Study on the formability, microstructures and mechanical properties of AlCrCuFeNix high-entropy alloys prepared by selective laser melting

Shuncun Luo, Zemin Wang*, Xiaoyan Zeng

Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and

Technology, Wuhan 430074, PR China

Abstract

Because of easy cracking caused by rapid solidification, fabricating dual-phase high-entropy alloys (DP-HEAs) through selective laser melting (SLM) has hardly been achieved. Here we reasonably design new DP-HEAs specific to SLM according to solid solutions formation criterion and HEA definition. Results show that Ni addition favors the formation of face-centered cubic (FCC) phase and facilitates the transition from columnar to equiaxed grains, thus the formability of AlCrCuFeNix (2.0 ≤ x ≤ 3.0) HEAs is improved. The SLMed AlCrCuFeNi3.0 HEA exhibits remarkably heterogeneous microstructures, such as modulated nanoscale lamellar or cellular dual-phase structures, and possesses the best combination of the ultimate tensile strength (~ 957 MPa) and ductility (~ 14.3 %). Also, it is discovered that high densities of Cr-enriched nano-precipitates are embedded in the ordered body-centered cubic (B2) phase. Finally, the underlying strengthening mechanisms are analyzed for the SLMed AlCrCuFeNi3.0 HEA. Keywords: High entropy alloy; Selective laser melting; Microstructure; Strength

Introduction

Due to their excellent mechanical properties, high entropy alloys (HEAs), as a new kind of multicomponent alloys containing at least five major elements, have attracted more and more attention from researchers [1 ,2 ]. HEAs favor forming simple solid solutions, such as face-centered cubic (FCC), body-centered cubic (BCC) and FCC + BCC, presumably owing to their ‘high ’ [1]. Generally, FCC HEAs exhibit excellent ductility but low strength. However, BCC HEAs show a contrary feature. Additionally, it is hard to realize a simultaneous increase of strength and ductility in single-phase HEAs because the lattice distortion induced strengthening and inherent solid solution strengthening are limited [3].

Intriguingly, dual-phase (DP) or multiple-phase HEAs have been reported to possess

superior synthetical properties principally arising from the phase metastability induced hardening and precipitation strengthening, which makes it a promising candidate for practical application in engineering [ 4 - 6 ]. Currently, the preparations of HEAs mainly depend on vacuum arc melting or casting [7], imposing high cost and enormous limitation to produce complex geometry shape.

However, selective laser melting (SLM), a high-efficient and economical laser additive

manufacturing (AM) technique, can rapidly fabricate metal components with a complex shape through successive deposition of raw powders layer-by-layer [8]. Recent researches suggest that the SLMed HEA parts exhibit nearly full densification and ultra-fine grains owing to rapid cooling rate (105~107 K/s) and high controllability of processing during SLM. This leads to better performance compared to that fabricated by casting [9]. Unfortunately, possibly due to * Corresponding author.

E-mail address: zmwang@hust.edu.cn (Z. Wang).

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Solid Freeform Fabrication 2019: Proceedings of the 30th Annual InternationalSolid Freeform Fabrication Symposium – An Additive Manufacturing Conference

Reviewed Paper

the inhibited formation of soft FCC phase and easy cracking induced by rapid solidification, processing FCC + BCC DP-HEAs through SLM has never been achieved [10,11]. Only SLMed single-phase FCC HEAs with high ductility have been extensively researched, such as FCC FeCoCrNi [12], C-containing FCC FeCoCrNi [13,14], FCC CoCrFeMnNi [15,16] HEAs.

To explore the feasibility of producing DP-HEA with high strength-ductility combination via SLM, the equiatomic AlCrCuFeNi alloy, as a representative SLMed single-phase BCC HEA [10], is switched to the non-equiatomic AlCrCuFeNix (x=2.0, 2.5, 2.75, 3.0) system, which exhibits partial transformation from BCC to FCC phase upon the addition of Ni according to the valence electron concentration (VEC) theory [ 17 ,18 ]. The configurational entropy of AlCrCuFeNi3 alloy is ~150% R (R denotes gas constant), and thus conforms well to the HEA definition. Recent studies indicate that the introduction of a ‘heterogeneous microstructure’ in metals or alloys can further contribute to achieving high strength-ductility combination, thus overcoming the strength-ductility trade-off [19-21]. Yet whether SLMed DP-HEAs also exhibit the heterogeneous microstructural features remains unclear. Little is known about the structure-property relationship for SLMed DP-HEAs. This study aims to examine the feasibility of SLM printing BCC + FCC DP-HEAs, and then disclose its heterogeneous microstructure as well as deformation behavior.

Experimental methods

In this work, argon gas atomized AlCrCuFeNi alloy powders with an average size of ~ 30.3 m [10], and Ni powders (purity larger than 99.8 wt.%) with a mean size of ~ 32 m were used as the original materials. Table 1 shows the chemical composition of AlCrCuFeNi powders. Before SLM processing, the two powders were mixed in the ball mill for 12 h to guarantee the homogeneous mixing of AlCrCuFeNi powders and Ni powders. The representative morphology of the mixed AlCrCuFeNi3 powders is shown in Fig. 1.

Table 1. Chemical composition of the raw AlCrCuFeNi alloy powders. Element Al Cr Cu Fe Ni

Wt.% 11.69 19.92 23.78 21.23 23.38 At.% 22.01 19.46 19.00 19.30 20.22

Fig. 1. SEM morphology of the mixed AlCrCuFeNi3 powders.

The SLM experiments were carried out in an argon atmosphere containing < 40 ppm O2 and H2O. Simultaneously considering the good formability and high relative density (>99.7%),

Ni

AlCrCuFeNi

626

the optimal processing parameters for producing AlCrCuFeNix (x=2.0, 2.5, 2.75, 3.0) HEAs via SLM were further optimized based on the previous investigation [10], as listed in Table 2.

Phase identification was carried out by using an X-ray diffractometer (XRD, x’pert3 powder) with Cu K radiation. The distribution of compositional elements of the as-SLMed sample was analyzed by electron probe microanalysis (EPMA 8050G). A scanning electron microscope (SEM, FEI Gemini SEM 300) equipped with a back-scattered electron (BSE) detector and an electron back (EBSD) system was applied to observe the microstructures along the building direction. Transmission electron microscopy (TEM) was carried out on Tecnai G2 F30 FEGTM operating at 300 kV. Using the optimal parameters, dog-bone-shaped tensile specimens with the gauge length of 20 mm, the thickness of 1.5 mm and width of 5 mm were printed along the build direction on a self-developed LSNF-1 SLM equipment. Using a Zwick testing machine, uniaxial tension experiments were carried out with a strain rate of 1 × 10 3 s 1 at room temperature. To ensure the data reproducibility, three repeated tests were performed.

Table 2. Optimized SLM processing parameters for preparing AlCrCuFeNix (x=2.0, 2.5, 2.75, 3.0) HEAs samples. Parameters Value

Laser power (W) 200 Scanning speed (mm/s) 400 Layer thickness (μm) 20 Hatching space (mm) 0.08

Results

Structures and formability

The XRD results of SLMed AlCrCuFeNix HEAs with different contents of Ni are shown in Fig. 2. It can be found that the FCC phase is present as x increases to 2.0, which confirms the transition from BCC to FCC phase upon the addition of Ni. With the further increase of Ni, the relative volume fraction deduced from the XRD diffraction pattern for FCC phase obviously increases while that of BCC decreases. A moderate amount of BCC phase (~ 11%) is still captured by XRD as x increases to 3.0. This clearly confirms that the AlCrCuFeNi3.0 HEA possesses dual-phase structures.

Fig. 2. XRD patterns of SLMed AlCrCuFeNix HEAs with different contents of Ni.

The BSE images of SLMed AlCrCuFeNix HEAs with various Ni content are shown in Fig.

20 40 60 80 100

• FCC♦ BCC/B2♦ ♦

♦♦

···x=2.0

x=2.5

x=2.75

x=3.0

2 Theta (Degree)

Inte

nsity

(a.u

.) ·♦

627

~ . --

J A

3. Obviously, the micro-cracks are largely eliminated with the increase of Ni content. Only traceamounts of micro-cracks appear in AlCrCuFeNi2.75 HEA. Finally, an increase to 3.0 Ni(AlCrCuFeNi3.0) completely eliminates the micro-cracks. Additionally, EPMA analysis resultsillustrate that the five principal elements of SLMed samples are nearly uniform distribution inthe sub-millimeter scale, verifying the homogeneous mixing of AlCrCuFeNi powders and Nipowders. Consequently, it can be concluded that a DP-HEA with good formability issuccessfully produced by SLM when x increases to 3.0. Then, the desired microstructures ofAlCrCuFeNi3.0 HEA are analyzed in detail in the following.

Fig. 3. Backscattered electron images of SLMed AlCrCuFeNix HEAs: (a) x=2.0; (b) x=2.5; (c) x=2.75; (d) x=3.0.

Microstructures

Fig. 4 (a-b) shows the SEM images of SLMed AlCrCuFeNi3 HEA along the building direction. Approximately equiaxed grains with different contrast are clearly observed (Fig. 4 (a)). Also, multiple ultrafine lamellar or cellular structures appear within the near-equiaxed grains. Meanwhile, the lamellar and cellular structures are usually interrupted at the grain boundaries, maybe contributing to the formation of near-equiaxed grains. Fig. 4 (b) shows the enlarged views of tiny lamellar structure. A large number of nano-precipitates with the mean size about 10 nm are present and distribute uniformly between the lamellar structures or cellular structures.

The bright-field TEM images further confirm the nano-sized lamellar and cellular structures of the SLMed AlCrCuFeNi3.0 HEA, as depicted in Fig. 4 (c) and (d), respectively.

(a) (b)

(c) (d)

628

10Dµm EHT= 1500kV t--------1 "-'.a,;i • 100 X \\1):7.9rrm

The selected area diffraction pattern (SADP) (the inset) in Fig. 4 (c) corresponding to the red circled region (Fig. 4 (c)) indicates the presence of disordered FCC phase. The clear superlattice spots marked by yellow circles in the SADP (the inset) in Fig. 4 (d) confirms that the blue circled region (Fig. 4 (c)) is ordered BCC (B2) phases. It was frequently reported that the strong negative mixing enthalpy of Al-Ni pair contributes to the formation of ordered B2 phase [22,23]. Meanwhile, the average thickness of FCC (~ 0.49 μm) in the lamellar regions is greater than that of the B2 phase (~ 0.14 m). Similarly, the cellular structures shown in Fig. 4 (d) belong to the FCC phases, while the narrow bright regions around the cellular boundaries belong to the B2 phases. The average diameter of these cellular structures is about 0.65 μm. Additionally, the dislocations appear to be emitted from the FCC/B2 phase boundaries and then patterned into the lamellar and cellular structures. But due to more dislocation slip systems in FCC structure than in BCC structure, the lamellar and cellular structures are observed to contain profuse dislocation networks in FCC phases, with relatively clean interiors of B2 phases. From the above, it can be concluded that the ultrafine lamellar regions consist of FCC and B2 lamellae, and the cellular non-lamellar regions compose of FCC cells with the B2 phases surrounded. Similar cellular structures were also discovered in laser additively manufactured 316L stainless steel [24].

Fig. 4. (a) SEM images along the building direction; (b) Enlarged view of lamellar structures

marked by red box in (a); (c) and (d) Bright-field TEM micrographs along the building direction; The insets SADPs correspond to the disordered FCC and ordered BCC (B2) phases,

respectively. The zone axes (Z.A.) of FCC and B2 phases are [011] and [011], respectively.

The scanning transmission electron microscopy (STEM) micrograph at high magnification is shown in Fig. 5 (a). Notably, the B2 lamellae contain profuse nano-precipitates, as observed by SEM. No secondary phases are discovered in the FCC lamellae. STEM-EDS elemental distribution maps (Fig. 5 (b)) of the yellow boxed region reveal that the B2 lamellae are

(a) (b)

(c)

FCC B2

(d)

629

enriched in Al and Cu, while the FCC lamellae are rich in Cr and Fe but depleted in Al and Cu elements. Also, the nano-precipitates are enriched in Cr. Such Cr-rich nano-precipitates embedded in B2 phases are first discovered in AlCrCuFeNi3.0 HEA although similar findings were reported in other HEAs [23,25,26].

Fig. 5 (c) shows the high-resolution TEM (HRTEM) image of a nano-precipitate inside B2 phase with [001] zone axis. The nano-precipitate with a diameter of about 10 nm is marked by the red dotted box. The Fast-Fourier-Transformation (FFT) pattern in the inset demonstrates that the nano-precipitates inside B2 phase are disordered BCC (A2) structures, then the matrix of the blue circled regions in Fig. 4 (c) and (d) should be the ordered BCC (B2) phase. Thus, it can be deduced that BCC phases are spinodally decomposed into a mixture of B2 phase plus A2 phase during SLM [10,23].

Fig. 5. (a) High magnification STEM image; (b) STEM-EDS maps of the yellow boxed region in (a); (c) HRTEM micrograph of a nano-precipitate inside B2 phase. Inset shows the

FFT pattern of the red boxed region corresponding to A2 nano-precipitate.

The typical microstructure analyzed by EBSD for the SLMed AlCrCuFeNi3.0 HEA is shown in Fig. 6 (a-b). Similarly, the grains under EBSD also present a near-equiaxed shape rather than a conventional columnar feature according to the inverse pole figure (IPF) in Fig. 6 (a). Meanwhile, a continuous variation of color and thus the change of orientation is clearly detected within one single grain, demonstrating that the near-equiaxed grains are filled with multiple ultrafine sub-structures. The GB map in Fig. 6 (b) shows that a significant fraction (~ 33.2% of total GBs) of low-angle grain boundaries (LAGBs, 2−15°) marked by white lines are detected within the near-equiaxed grains.

(a)

Cr Al

Fe Cu Ni

(b)

FCC B2+A2

A2

A2 Z.A.=[001]

(c)

B2 matrix

A2

630

Fig. 6 (c-d) show the microstructural characteristic within one single grain at a higher magnification. It can be observed that the FCC (red) and B2 (blue) phases in alternating lamellar morphology are indexed in EBSD phase map at the nanoscale (Fig. 6 (c)). These are in fairly good accordance with the results observed from TEM. Based on the EBSD phase map, the volume fraction of FCC and B2 phases is calculated to be about 89.2% and 10.4%, respectively. The corresponding kernel average misorientations (KAMs) marked as rainbow ranging from 0° to 2° are illustrated in Fig. 6 (d). Local misorientations across lamellar structures are clearly present, demonstrating the existence of high lattice distortions, particularly in the vicinity of FCC/B2 phase boundaries. The dislocation multiplication and accumulation induced by rapid solidification may significantly contribute to the high lattice distortion.

Fig. 6. (a) EBSD IPF map; (b) EBSD image quality (IQ) map with HAGBs (blue lines) and LAGBs (white lines) superimposed; (c) Phase map of magnified lamellar structures and (d)

corresponding KAM map.

Based on the above analyzation, it can be concluded that the SLMed AlCrCuFeNi3.0 HEA exhibits remarkably heterogeneous microstructures, both structural and chemical, including micron-sized near-equiaxed grains, nanoscale lamellar or cellular dual-phase structures, LAGBs, dislocations, nano-precipitates, and segregated elements (such as Cr, Al, and Cu). That is, the microstructure presents a multi-scale feature, nearly spanning from nanometre to sub-millimeter. The particular interests are the profuse A2 nano-precipitates embedded in B2 phases, as well as the solidification nanoscale lamellar or cellular dual-phase structure. These are scarcely observed in other reported SLMed HEAs [9-16].

Mechanical properties

Fig. 7 shows the tensile mechanical properties of SLMed AlCrCuFeNix (x=2.0, 2.5, 2.75, 3.0) HEAs. Due to the existence of many micro-cracks, the properties of AlCrCuFeNix (x=2.0, 2.5) HEAs are poor. However, the AlCrCuFeNi3 HEA exhibits the best combination of the

(a) (b)

(c) (d)

631

ultimate tensile strength (~ 957 MPa) and ductility (~ 14.3%). Comparing the strength and elongation of selected HEAs, the synthetic mechanical properties of SLMed AlCrCuFeNi3 HEA are superior to other SLMed HEAs [9,12-16], as-cast and cold-rolled plus annealed AlCrCuFeNi HEA system [27].

Fig. 7. Tensile mechanical properties of SLMed AlCrCuFeNix (x=2.0, 2.5, 2.75, 3.0) HEAs.

It is considered that each element in HEA can be acted as solute atoms [1]. This can trigger a huge Cottrell atmosphere in the dislocation field, thus locking the dislocation [28]. Then, large drag forces on dislocations will be induced by abundant solutes atoms, and more tensile forces are necessary to make the dislocation free from this atmosphere. Consequently, the tensile stress significantly increases. Once the applied forces become sufficiently large, dislocations will escape from the lock of Cottrell atmosphere and move to the next obstacle with small stress. Additionally, the profuse highly coherent A2 nano-precipitates can effectively pin and drag dislocations in terms of the Orowan mechanism [26], thereby largely strengthening the B2 phase. Therefore, similar to the solute atoms, the profuse coherent A2 nano-precipitates can also serve as the obstacles of hindering moving dislocations. The continually pinning and unpinning of dislocations lead to the high ultimate tensile strength.

Additionally, it has been reported that the pronounced strengthening in heterogeneous materials is ascribed to the effect of back stress [19,21]. First, both FCC and B2 lamellas experience elastic deformation in a similar manner. Then, the hard B2 lamellas continue to elastically deform when the soft FCC lamellas start deforming plastically. The A2 precipitation strengthening makes the B2 lamellas harder to be deformed, aggravating the incompatibility of deformation. Thus, geometrically necessary dislocations (GNDs) are needed to accommodate this deformation incompatibility [ 29 ]. The accumulated GNDs can result in distinctly strengthening of the soft FCC lamellas through cross-slip mechanisms and forest hardening. Consequently, the yield strength is significantly improved. Finally, both FCC and B2 lamellas undergo plastically deforming, but the soft FCC lamellas are subjected to severer deformation, introducing strain partitioning [30]. As a result, strain gradients are built up near the FCC/B2 interfaces. The strain gradient increases with the strain partitioning increasing, thereby generating distinct back stress strengthening. The back stress strengthening is believed to prevent early local necking and then enhances the strength and ductility [29].

Similarly, the soft FCC cells with the hard B2 phases surrounded can produce profuse boundaries separating domains with different hardness. Consequently, a high density of GNDs will pile up at the FCC/B2 phase boundaries, which is particularly favorable to induce significant back stress strengthening. Moreover, the back stress, in turn, results in strain

0

200

400

600

800

1000

0

4

8

12

16

20

3.02.752.5

Frac

ture

elo

ngat

ion

(%)

Stre

ngth

(MPa

)

Ni atomic ratio

Yield strength Ultimate tensile strength Fracture elongation

2.0

632

-D -

repartitions and a change of internal stresses, which may result in a high flow stress. However, further studies are needed to verify this possible mechanism. In conclusion, the lamellar or cellular dual-phase microstructures featured by a mixture of soft FCC and hard B2 phases exhibit a nano-scale structural hierarchy, which leads to the high ultimate tensile strength and good tensile ductility of SLMed AlCrCuFeNi3 HEA.

Conclusions

In summary, (FCC+BCC) DP-HEAs are first fabricated by the SLM technique. The SLMed AlCrCuFeNi3 HEA exhibits heterogeneous microstructures, thus producing high strength and good ductility simultaneously. The feasibility of SLM additive manufacturing technique to prepare AlCrCuFeNix (x=2.0, 2.5, 2.75, 3.0) DP-HEAs is explored. It is revealed that Ni addition favors the formation of FCC phases and improves the formability. The Cottrell atmosphere effect, A2 precipitation hardening and back stress strengthening induced by heterogeneous microstructures contribute to the high ultimate tensile strength (~ 957 MPa) and good ductility (~ 14.3 %) of SLMed AlCrCuFeNi3.0 HEA.

Acknowledgments

This work was supported financially by the Pre-research Fund Project of Ministry of Equipment and Development of China (No. 61409230301), and the Fundamental Research Funds for the Central Universities through Program No.2019kfyXMPY005 and No.2019kfyXKJC042.

References

[1] J.W. Yeh, S.K. Chen, S.J. Lin, et al. Nanostructured high entropy alloys with multipleprincipal elements: novel alloy design concepts and outcomes, Adv Eng Mater. 6(5)(2004) 299–303.

[2] B. Gludovatz, A. Hohenwarter, D. Catoor, E.H. Chang, E.P. George, R.O. Ritchie, A fracture-resistant high-entropy alloy for cryogenic applications, Science. 345 (2014)1153–1158.

[3] L.R. Owen, E.J. Pickering, H.Y. Playford, et al. An assessment of the lattice strain in theCrMnFeCoNi high-entropy alloy, Acta Mater. 122 (2017) 11–18.

[4] Z. Li, K.G. Pradeep, Y. Deng, et al. Metastable high-entropy dual-phase alloys overcomethe strength- 227–230.

[5] T. Yang, Y.L. Zhao, Y. Tong, Z.B. Jiao, J. Wei, J.X. Cai, X.D. Han, D. Chen, A. Hu, J.J.Kai, K. Lu, Y. Liu, C.T. Liu, Multicomponent intermetallic nanoparticles and superbmechanical behaviors of complex alloys, Science. 362 (2018) 933–937.

[6] T. Bhattacharjee, I.S. Wani, S. Sheikh, I.T. Clark, T. Okawa, S. Guo, P.P. Bhattacharjee, N.Tsuji, Simultaneous Strength-Ductility Enhancement of a Nano-Lamellar AlCoCrFeNi2.1Eutectic High Entropy Alloy by Cryo-Rolling and Annealing, Sci. Rep. 8 (2018) 3276.

[7] B. Gwalani, V. Soni, D. Choudhuri, M. Lee, J.Y. Hwang, S.J. Nam, H. Ryu, S.H. Hong, R.Banerjee, Stability of ordered L12 and B2 precipitates in face centered cubic based highentropy alloys - Al0.3CoFeCrNi and Al0.3CuFeCrNi2, Scr. Mater. 123 (2016) 130–134.

[8] Z.M. Wang, K. Guan, M. Gao, X.Y. Li, X.F. Chen, X.Y. Zeng, The microstructure andmechanical properties of deposited-IN718 by selective laser melting, J. Alloy Compd. 513(2012) 518–523.

[9] P.F. Zhou, D.H. Xiao, Z. Wu, X.Q. Ou, Al0.5FeCoCrNi high entropy alloy prepared byselective laser melting with gas-atomized pre-alloy powders, Mater. Sci. Eng. A. 739

633

(2019) 86–89. [10] S.C. Luo, P. Gao, H.C. Yu, J.J. Yang, Z.M. Wang, X.Y. Zeng, Selective laser melting of

an equiatomic AlCrCuFeNi high-entropy alloy: Processability, non-equilibriummicrostructure and mechanical behavior, J. Alloys Compd. 771 (2019) 387–397.

[11] P. D. Niu, R. D. Li, T. C. Yuan, S. Y. Zhu, C. Chen, M. B. Wang, L. Huang,Microstructures and properties of an equimolar AlCoCrFeNi high entropy alloy printedby selective laser melting, Intermetallics. 104 (2019) 24–32.

[12] Y. Brif, M. Thomas, I. Todd, The use of high-entropy alloys in additive manufacturing,Scr. Mater. 99 (2015) 93–96.

[13] W.Q. Wu, R. Zhou, B.Q. Wei, S. Ni, Y. Liu, M. Song, Nanosized precipitates anddislocation networks reinforced C-containing CoCrFeNi high-entropy alloy fabricated byselective laser melting, Mater. Charact. 144 (2018) 605–610.

[14] R. Zhou, Y. Liu, C.S. Zhou, S.Q. Li, W.Q. Wu, M. Song, B. Liu, X.P. Liang, P.K. Liaw,Microstructures and mechanical properties of C-containing FeCoCrNi high-entropy alloyfabricated by selective laser melting, Intermetallics. 94 (2018) 165–171.

[15] Z.G. Zhu, Q.B. Nguyen, F.L. Ng, X.H. An, X.Z. Liao, P.K. Liaw, S.M.L. Nai, J. Wei,Hierarchical microstructure and strengthening mechanisms of a CoCrFeNiMn highentropy alloy additively manufactured by selective laser melting, Scr. Mater. 154 (2018)20–24.

[16] R.D. Li, P.D. Niu, T.C. Yuan, P. Cao, C. Chen, K.C. Zhou, Selective laser melting of anequiatomic CoCrFeMnNi high-entropy alloy: Processability, non-equilibriummicrostructure and mechanical property, J. Alloys Compd. 746 (2018) 125–134.

[17] S. Guo, C. Ng, J. Lu, C.T. Liu, Effect of valence electron concentration on stability of fccor bcc phase in high entropy alloys, J. Appl. Phys. 109 (2011) 103505.

[18] T. Yang, Y.L. Zhao, W.H. Liu, J.H. Zhu, J.J. Kai, C.T. Liu, Y.L. Zhao, W.H. Liu, J.H.Zhu, J.J. Kai, C.T. Liu, Ductilizing brittle high-entropy alloys via tailoring valenceelectron concentrations of precipitates by controlled elemental partitioning, Mater. Res.Lett. 10 (2018) 600–606.

[19] Z.Q. Fu, B.E. MacDonald, Z.M. Li, Z.F. Jiang, W.P. Chen, Y.Z. Zhou, E.J. Lavernia,Engineering heterostructured grains to enhance strength in a single-phase high-entropyalloy with maintained ductility, Mater. Res. Lett. 6 (2018) 634–640.

[20] S. Shukla, D. Choudhuri, T.H. Wang, K.M. Liu, R. Wheeler, S. Williams, B. Gwalani,R.S. Mishra, Hierarchical features infused heterogeneous grain structure forextraordinary strength-ductility synergy, Mater. Res. Lett. 6 (2018) 676–682.

[21] J. Su, D. Raabe, Z.M. Li, Hierarchical microstructure design to tune the mechanicalbehavior of an interstitial TRIP-TWIP high-entropy alloy, Acta Mater. 163 (2019) 40–54.

[22] C. Li, M. Zhao, J.C. Li, B2 structure of high-entropy alloys with addition of Al. J ApplPhys. 104 (2008) 113504.

[23] J.Y. He, W.H. Liu, H. Wang, Y. Wu, X.J. Liu, T.G. Nieh, Z.P. Lu, Effects of Al additionon structural evolution and tensile properties of the FeCoNiCrMn high-entropy alloysystem, Acta Mater. 62 (2014) 105–113.

[24] Y.M. Wang, T. Voisin, J.T. McKeown, J. Ye, N.P. Calta, Z. Li, Z. Zeng, Y. Zhang, W.Chen, T.T. Roehling, R.T. Ott, M.K. Santala, P.J. Depond, M.J. Matthews, A. V. Hamza,T. Zhu, Additively manufactured hierarchical stainless steels with high strength andductility, Nat. Mater. 17 (2018) 63–70.

[25] D. Choudhuri, B. Gwalani, S. Gorsse, C. V. Mikler, R. V. Ramanujan, M. A. Gibson, R.Banerjee, Change in the primary solidification phase from fcc to bcc-based B2 in highentropy or complex concentrated alloys, Scr. Mater. 127 (2017) 186–190.

[26] X. Gao, Y. Lu, B. Zhang, N. Liang, G. Wu, G. Sha, J. Liu, Y. Zhao, Microstructuralorigins of high strength and high ductility in an AlCoCrFeNi2.1 eutectic high-entropy

634

alloy, Acta Mater. 141 (2017) 59–66. [27] S.G. Ma, J.W. Qiao, Z.H. Wang, H.J. Yang, Y. Zhang, Microstructural features and tensile

behaviors of the Al0.5CrCuFeNi2 high-entropy alloys by cold rolling and subsequentannealing, Mater. Des. 88 (2015) 1057–1062.

[28] A.H. Cottrell, B.A. Bilby, Dislocation theory of yielding and strain ageing of iron, ProcPhys Soci. Section A. 62 (1949) 49.

[29] E. Ma, T. Zhu, Towards strength–ductility synergy through the design of heterogeneousnanostructures in metals, Mater. Today. 20 (2017) 323–331.

[30] M.X. Yang, Y. Pan, F.P. Yuan, Y.T. Zhu, X.L. Wu, Back stress strengthening and strainhardening in gradient structure, Mater. Res. Lett. 4 (2016) 145–151.

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Data AnalyticsPredicting and Controlling the Thermal Part History in Powder Bed Fusion Using Neural Networks‘Seeing’ the Temperature inside the Part during the Powder Bed Fusion ProcessConditional Generative Adversarial Networks for In-Situ Layerwise Additive Manufacturing DataIn-Situ Layer-Wise Quality Monitoring for Laser-Based Additive Manufacturing Using Image Series AApplications of Supervised Machine Learning Algorithms in Additive Manufacturing: A ReviewReal-Time 3D Surface Measurement in Additive Manufacturing Using Deep LearningRoughness Parameters for Classification of As-Built and Laser Post-Processed Additive Manufactured SurfacesApplication of the Fog Computing Paradigm to Additive Manufacturing Process Monitoring and ControlSpectral X-ray CT for Fast NDT Using Discrete Tomography

Hybrid AMPart Remanufacturing Using Hybird Manufacturing ProcessesIntegration Challenges with Additive/Subtractive In-Envelope Hybrid ManufacturingRobot-Based Hybrid Manufacturing Process ChainIntegrated Hardfacing of Stellite-6 Using Hybrid Manufacturing ProcessInkjet Printing of Geometrically Optimized Electrodes for Lithium-Ion Cells: A Concept for a Hybrid Process ChainUltrasonic Embedding of Continuous Carbon Fiber into 3D Printed Thermoplastic Parts

Materials: MetalsComparison of Fatigue Performance between Additively Manufactured and Wrought 304L Stainless Steel Using a Novel Fatigue Test SetupElevated Temperature Mechanical and Microstructural Characterization of SLM SS304LFatigue Behavior of Additive Manufactured 304L Stainless Steel Including Surface Roughness EffectsJoining of Copper and Stainless Steel 304L Using Direct Metal DepositionSS410 Process Development and CharacterizationEffect of Preheating Build Platform on Microstructure and Mechanical Properties of Additively Manufactured 316L Stainless SteelCharacterisation of Austenitic 316LSi Stainless Steel Produced by Wire Arc Additive Manufacturing with Interlayer CoolingEffects of Spatial Energy Distribution on Defects and Fracture of LPBF 316L Stainless SteelEnvironmental Effects on the Stress Corrosion Cracking Behavior of an Additively Manufactured Stainless SteelEffect of Powder Chemical Composition on Microstructures and Mechanical Properties of L-PBF Processed 17-4 PH Stainless Steel in the As-Built And Hardened-H900 ConditionsPowder Variation and Mechanical Properties for SLM 17-4 PH Stainless SteelFatigue Life Prediction of Additive Manufactured Materials Using a Defect Sensitive ModelEvaluating the Corrosion Performance of Wrought and Additively Manufactured (AM) Invar ® and 17-4PHComparison of Rotating-Bending and Axial Fatigue Behaviors of LB-PBF 316L Stainless SteelA Study of Pore Formation during Single Layer and Multiple Layer Build by Selective Laser MeltingDimensional Analysis of Metal Powder Infused Filament - Low Cost Metal 3D PrintingAdditive Manufacturing of Fatigue Resistant Materials: Avoiding the Early Life Crack Initiation Mechanisms during FabricationAdditive Manufacturing of High Gamma Prime Nickel Based Superalloys through Selective Laser Melting (SLM)Investigating the Build Consistency of a Laser Powder Bed Fused Nickel-Based Superalloy, Using the Small Punch TechniqueFatigue Behavior of Laser Beam Directed Energy Deposited Inconel 718 at Elevated TemperatureVery High Cycle Fatigue Behavior of Laser Beam-Powder Bed Fused Inconel 718Analysis of Fatigue Crack Evolution Using In-Situ TestingAn Aluminum-Lithium Alloy Produced by Laser Powder Bed FusionWire-Arc Additive Manufacturing: Invar Deposition CharacterizationStudy on the Formability, Microstructures and Mechanical Properties of Alcrcufeniᵪ High-Entropy Alloys Prepared by Selective Laser MeltingLaser-Assisted Surface Defects and Pore Reduction of Additive Manufactured Titanium PartsFatigue Behavior of LB-PBF Ti-6Al-4V Parts under Mean Stress and Variable Amplitude Loading ConditionsInfluence of Powder Particle Size Distribution on the Printability of Pure Copper for Selective Laser MeltingInvestigation of the Oxygen Content of Additively Manufactured Tool Steel 1.2344The Porosity and Mechanical Properties of H13 Tool Steel Processed by High-Speed Selective Laser MeltingFeasibility Analysis of Utilizing Maraging Steel in a Wire Arc Additive Process for High-Strength Tooling ApplicationsInvestigation and Control of Weld Bead at Both Ends in WAAM

Materials: PolymersProcess Parameter Optimization to Improve the Mechanical Properties of Arburg Plastic Freeformed ComponentsImpact Strength of 3D Printed Polyether-Ether-Ketone (PEEK)Mechanical Performance of Laser Sintered Poly(Ether Ketone Ketone) (PEKK)Influence of Part Microstructure on Mechanical Properties of PA6X Laser Sintered SpecimensOptimizing the Tensile Strength for 3D Printed PLA PartsCharacterizing the Influence of Print Parameters on Porosity and Resulting DensityCharacterization of Polymer Powders for Selective Laser SinteringEffect of Particle Rounding on the Processability of Polypropylene Powder and the Mechanical Properties of Selective Laser Sintering Produced PartsProcess Routes towards Novel Polybutylene Terephthalate – Polycarbonate Blend Powders for Selective Laser SinteringImpact of Flow Aid on the Flowability and Coalescence of Polymer Laser Sintering PowderCuring and Infiltration Behavior of UV-Curing Thermosets for the Use in a Combined Laser Sintering Process of PolymersRelationship between Powder Bed Temperature and Microstructure of Laser Sintered PA12 PartsUnderstanding the Influence of Energy-Density on the Layer Dependent Part Properties in Laser-Sintering of PA12Tailoring Physical Properties of Shape Memory Polymers for FDM-Type Additive ManufacturingInvestigation of The Processability of Different Peek Materials in the FDM Process with Regard to the Weld Seam StrengthStereolithography of Natural Rubber Latex, a Highly Elastic Material

Materials: Ceramics and CompositesMoisture Effects on Selective Laser Flash Sintering of Yttria-Stabilized ZirconiaThermal Analysis of Thermoplastic Materials Filled with Chopped Fiber for Large Area 3D PrintingThermal Analysis of 3D Printed Continuous Fiber Reinforced Thermoplastic Polymers for Automotive ApplicationsCharacterization of Laser Direct Deposited Magnesium Aluminate Spinel CeramicsTowards a Micromechanics Model for Continuous Carbon Fiber Composite 3D Printed PartsEffect of In-Situ Compaction and UV-Curing on the Performance of Glass Fiber-Reinforced Polymer Composite Cured Layer by Layer3D Printing of Compliant Passively Actuated 4D StructuresEffect of Process Parameters on Selective Laser Melting Al₂O₃-Al Cermet MaterialStrengthening of 304L Stainless Steel by Addition of Yttrium Oxide and Grain Refinement during Selective Laser MeltingApproach to Defining the Maximum Filler Packing Volume Fraction in Laser Sintering on the Example of Aluminum-Filled Polyamide 12Laser Sintering of Pine/Polylatic Acid CompositesCharacterization of PLA/Lignin Biocomposites for 3D PrintingElectrical and Mechancial Properties of Fused Filament Fabrication of Polyamide 6 / Nanographene Filaments at Different Annealing TemperaturesManufacturing and Application of PA11-Glass Fiber Composite Particles for Selective Laser SinteringManufacturing of Nanoparticle-Filled PA11 Composite Particles for Selective Laser SinteringTechnique for Processing of Continuous Carbon Fibre Reinforced Peek for Fused Filament FabricationProcessing and Characterization of 3D-Printed Polymer Matrix Composites Reinforced with Discontinuous FibersTailored Modification of Flow Behavior and Processability of Polypropylene Powders in SLS by Fluidized Bed Coating with In-Situ Plasma Produced Silica Nanoparticles

ModelingAnalysis of Layer Arrangements of Aesthetic Dentures as a Basis for Introducing Additive ManufacturingComputer-Aided Process Planning for Wire Arc Directed Energy DepositionMulti-Material Process Planning for Additive ManufacturingCreating Toolpaths without Starts and Stops for Extrusion-Based SystemsFramework for CAD to Part of Large Scale Additive Manufacturing of Metal (LSAMM) in Arbitrary DirectionsA Standardized Framework for Communicating and Modelling Parametrically Defined Mesostructure PatternsA Universal Material Template for Multiscale Design and Modeling of Additive Manufacturing Processes

Physical ModelingModeling Thermal Expansion of a Large Area Extrusion Deposition Additively Manufactured Parts Using a Non-Homogenized ApproachLocalized Effect of Overhangs on Heat Transfer during Laser Powder Bed Fusion Additive ManufacturingMelting Mode Thresholds in Laser Powder Bed Fusion and Their Application towards Process Parameter DevelopmentComputational Modelling and Experimental Validation of Single IN625 Line Tracks in Laser Powder Bed FusionValidated Computational Modelling Techniques for Simulating Melt Pool Ejecta in Laser Powder Bed Fusion ProcessingNumerical Simulation of the Temperature History for Plastic Parts in Fused Filament Fabrication (FFF) ProcessMeasurement and Analysis of Pressure Profile within Big Area Additive Manufacturing Single Screw ExtruderNumerical Investigation of Extrusion-Based Additive Manufacturing for Process Parameter Planning in a Polymer Dispensing SystemAlternative Approach on an In-Situ Analysis of the Thermal Progression during the LPBF-M Process Using Welded Thermocouples Embedded into the Substrate PlateDynamic Defect Detection in Additively Manufactured Parts Using FEA SimulationSimulation of Mutually Dependent Polymer Flow and Fiber Filled in Polymer Composite Deposition Additive ManufacturingSimulation of Hybrid WAAM and Rotation Compression Forming ProcessDimensional Comparison of a Cold Spray Additive Manufacturing Simulation ToolSimulated Effect of Laser Beam Quality on the Robustness of Laser-Based AM SystemA Strategy to Determine the Optimal Parameters for Producing High Density Part in Selective Laser Melting ProcessRheology and Applications of Particulate Composites in Additive ManufacturingComputational Modeling of the Inert Gas Flow Behavior on Spatter Distribution in Selective Laser MeltingPrediction of Mechanical Properties of Fused Deposition Modeling Made Parts Using Multiscale Modeling and Classical Laminate Theory

Process DevelopmentThe Use of Smart In-Process Optical Measuring Instrument for the Automation of Additive Manufacturing ProcessesDevelopment of a Standalone In-Situ Monitoring System for Defect Detection in the Direct Metal Laser Sintering ProcessFrequency Inspection of Additively Manufactured Parts for Layer Defect IdentificationMelt Pool Monitoring for Control and Data Analytics in Large-Scale Metal Additive ManufacturingFrequency Domain Measurements of Melt Pool Recoil Pressure Using Modal Analysis and Prospects for In-Situ Non-Destructive TestingInterrogation of Mid-Build Internal Temperature Distributions within Parts Being Manufactured via the Powder Bed Fusion ProcessReducing Computer Visualization Errors for In-Process Monitoring of Additive Manufacturing Systems Using Smart Lighting and Colorization SystemA Passive On-line Defect Detection Method for Wire and Arc Additive Manufacturing Based on Infrared ThermographyExamination of the LPBF Process by Means of Thermal Imaging for the Development of a Geometric-Specific Process ControlAnalysis of the Shielding Gas Dependent L-PBF Process Stability by Means of Schlieren and Shadowgraph TechniquesApplication of Schlieren Technique in Additive Manufacturing: A ReviewWire Co-Extrusion with Big Area Additive ManufacturingSkybaam Large-Scale Fieldable Deposition Platform System ArchitectureDynamic Build Bed for Additive ManufacturingEffect of Infrared Preheating on the Mechanical Properties of Large Format 3D Printed PartsLarge-Scale Additive Manufacturing of Concrete Using a 6-Axis Robotic Arm for Autonomous Habitat ConstructionOverview of In-Situ Temperature Measurement for Metallic Additive Manufacturing: How and Then WhatIn-Situ Local Part Qualification of SLM 304L Stainless Steel through Voxel Based Processing of SWIR Imaging DataNew Support Structures for Reduced Overheating on Downfacing Regions of Direct Metal Printed PartsThe Development Status of the National Project by Technology Research Assortiation for Future Additive Manufacturing (TRAFAM) in JapanInvestigating Applicability of Surface Roughness Parameters in Describing the Metallic AM ProcessA Direct Metal Laser Melting System Using a Continuously Rotating Powder BedEvaluation of a Feed-Forward Laser Control Approach for Improving Consistency in Selective Laser SinteringElectroforming Process to Additively Manufactured Microscale StructuresIn-Process UV-Curing of Pasty Ceramic CompositeDevelopment of a Circular 3S 3D Printing System to Efficiently Fabricate Alumina Ceramic ProductsRepair of High-Value Plastic Components Using Fused Deposition ModelingA Low-Cost Approach for Characterizing Melt Flow Properties of Filaments Used in Fused Filament Fabrication Additive ManufacturingIncreasing the Interlayer Bond of Fused Filament Fabrication Samples with Solid Cross-Sections Using Z-PinningImpact of Embedding Cavity Design on Thermal History between Layers in Polymer Material Extrusion Additive ManufacturingDevelopment of Functionally Graded Material Capabilities in Large-Scale Extrusion Deposition Additive ManufacturingUsing Non-Gravity Aligned Welding in Large Scale Additive Metals Manufacturing for Building Complex PartsThermal Process Monitoring for Wire-Arc Additive Manufacturing Using IR CamerasA Comparative Study between 3-Axis and 5-Axis Additively Manufactured Samples and Their Ability to Resist Compressive LoadingUsing Parallel Computing Techniques to Algorithmically Generate Voronoi Support and Infill Structures for 3D Printed ObjectsExploration of a Cable-Driven 3D Printer for Concrete Tower Structures

ApplicationsTopology Optimization for Anisotropic Thermomechanical Design in Additive ManufacturingCellular and Topology Optimization of Beams under Bending: An Experimental StudyAn Experimental Study of Design Strategies for Stiffening Thin Plates under CompressionMulti-Objective Topology Optimization of Additively Manufactured Heat ExchangersA Mold Insert Case Study on Topology Optimized Design for Additive ManufacturingDevelopment, Production and Post-Processing of a Topology Optimized Aircraft BracketManufacturing Process and Parameters Development for Water-Atomized Zinc Powder for Selective Laser Melting FabricationA Multi-Scale Computational Model to Predict the Performance of Cell Seeded Scaffolds with Triply Periodic Minimal Surface GeometriesMulti-Material Soft Matter Robotic Fabrication: A Proof of Concept in Patient-Specific Neurosurgical SurrogatesOptimization of the Additive Manufacturing Process for Geometrically Complex Vibro-Acoustic MetamaterialsEffects of Particle Size Distribution on Surface Finish of Selective Laser Melting PartsAn Automated Method for Geometrical Surface Characterization for Fatigue Analysis of Additive Manufactured PartsA Design Method to Exploit Synergies between Fiber-Reinforce Composites and Additive Manufactured ProcessesPreliminary Study on Hybrid Manufacturing of the Electronic-Mechanical Integrated Systems (EMIS) via the LCD Stereolithography TechnologyLarge-Scale Thermoset Pick and Place Testing and ImplementationThe Use of Smart In-Process Optical Measuring Instrument for the Automation of Additive Manufacturing ProcessesWet-Chemical Support Removal for Additive Manufactured Metal PartsAnalysis of Powder Removal Methods for EBM Manufactured Ti-6Al-4V PartsTensile Property Variation with Wall Thickness in Selective Laser Melted PartsMethodical Design of a 3D-Printable Orthosis for the Left Hand to Support Double Bass Perceptional TrainingPrinted Materials and Their Effects on Quasi-Optical Millimeter Wave Guide Lens SystemsPorosity Analysis and Pore Tracking of Metal AM Tensile Specimen by Micro-CtUsing Wax Filament Additive Manufacturing for Low-Volume Investment CastingFatigue Performance of Additively Manufactured Stainless Steel 316L for Nuclear ApplicationsFailure Detection of Fused Filament Fabrication via Deep LearningSurface Roughness Characterization in Laser Powder Bed Fusion Additive ManufacturingCompressive and Bending Performance of Selectively Laser Melted AlSi10Mg StructuresCompressive Response of Strut-Reinforced Kagome with Polyurethane ReinforcementA Computational and Experimental Investigation into Mechanical Characterizations of Strut-Based Lattice StructuresThe Effect of Cell Size and Surface Roughness on the Compressive Properties of ABS Lattice Structures Fabricated by Fused Deposition ModelingEffective Elastic Properties of Additively Manufactured Metallic Lattice Structures: Unit-Cell ModelingImpact Energy Absorption Ability of Thermoplastic Polyurethane (TPU) Cellular Structures Fabricated via Powder Bed FusionPermeability Analysis of Polymeric Porous Media Obtained by Material Extrusion Additive ManufacturingEffects of Unit Cell Size on the Mechanical Performance of Additive Manufactured Lattice StructuresMechanical Behavior of Additively-Manufactured Gyroid Lattice Structure under Different Heat TreatmentsFast and Simple Printing of Graded Auxetic StructuresCompressive Properties Optimization of a Bio-Inspired Lightweight Structure Fabricated via Selective Laser MeltingIn-Plane Pure Shear Deformation of Cellular Materials with Novel Grip DesignModelling for the Tensile Fracture Characteristic of Cellular Structures under Tensile Load with Size EffectDesign, Modeling and Characterization of Triply Periodic Minimal Surface Heat Exchangers with Additive ManufacturingInvestigating the Production of Gradient Index Optics by Modulating Two-Photon Polymerisation Fabrication ParametersAdditive Manufactured Lightweight Vehicle Door Hinge with Hybrid Lattice Structure

Attendee ListAuthor Index