Alumina Reinforced High Porosity Al-alloys with Extreme Hardness

Alumina Reinforced High Porosity Al-alloys with

Extreme Hardness

Dr. László A. Gömze1, University of Miskolc,

Miskolc, Hungary

Tel.: +36 30 746 [email protected]

Zellulare Werkstoffe May 10-11, 2011, Freiberg, Germany

Ludmila N. Gömze2, IGREX Engineering Service Ltd.

Igrici, Hungary

Tel.: +36 30 746 [email protected]

Our Aims

On the basis of industry requirements develop ceramic reinforced low density new material compositions with some extreme mechanical properties as:

• dynamic strength, • hardness, • wear resistance.

.

Alumina Reinforced High Porosity Al-alloys with Extreme Hardness [email protected] http://keramia.uni-miskolc.hu [email protected]


• On the basis of ceramic matrices develop hetero-modulus and hetero-viscous complex material systems to save transport and flying equipment from collisions and hits with metallic and other bodies at speeds of:

v ≥ 1000 m/s.

• Develop high porosity, low density hetero-modulus ceramic reinforced composites of light metal alloys with increased hardness and wear resistance.



Our main research directions

• Multiple values of Young’s modulus

• High damage tolerance

• Ability to absorb and dissipate the elastic energy during crack propagation

• Good thermal shock resistance



Advantages of Hetero-Modulus Materials

Advantages of Hetero-Modulus and Hetero-Viscous Complex Materials

• High damage tolerance• Higher deformation tolerance• Ability to absorb and

dissipate the collision energy• Relax by time mechanical

stress developed in body during high speed collisions.



Some Complex Materials Having Excellent Dynamic Strength

Automobile tyres Asphalt mixturesCeramics made from hetero-modulus and

hetero-viscous particles





Typical Destruction of Ceramic Composites Under High Speed (HS) Collisions (u≥1000 m/sec)

Typical destruction of ceramic composites (L=3 mm) during high speed collision

Typical destruction of ceramic composites (L=4 mm) during high speed collisions

The Energy Engorgement Through Fractures and Deformation of Hetero-Modulus and Hetero-Viscous Complex Materials during high speed

collision• Complex material has several Young’s modulus (E=var.) and viscosity (η=var.)• Flying (hit) object has inhomogeneous density (ρ≠const.)

ρi: density of the „i-th” component of flying object; [kg/m3]

A1j and A2j: surface of fractures of „j-th” Young’s modulus component of hetero-modulus body [m2]

A3j: surface of deformed „j-th” Young’s modulus component of hetero-modulus body [m2]Ej: The Young’s modulus of the „j-th” component of hetero-modulus body ; [N/m2]

i=1, 2, …, n: the number of different density components of flying objectj=1, 2, …, n: the number of different Young’s modulus components of hetero-modulus body l1j and l2j: deep and „movement” of fractures of „j-th” Young’s modulus component of hetero-modulus body [m]

l3j: Size of deformation of „j-th” Young’s modulus component of hetero-modulus body [m]RPj and RSj: the pressure and shear strength of „j-th” Young’s modulus component of hetero-modulus body [N/m2]

Vi: volume of „i-th” component of flying object [m3]

K

kkkk

M

jjjjspH

n

iii lAlAEWWWVu

144

133

1

2

2



The General Equation of Shear Stress Relaxation in Complex Hetero-Modulus and Hetero-Viscous Ceramics after High Speed

Collision

CDeCeC

tAC

AB

ABt

AC

AB

AB

2

2

2

2

422

421

Where:

C1 and C2: constants of integration



• Having multiple values of Young’s modulus therefore these composite materials have ability to absorb and dissipate the elastic energy during crack propagation.

• Thanking to ceramic particles these material compositions have better hardness and wear resistancy.

• Due to metallic parts these hetero-modulus composite materials have much higher thermal conductivities and better thermal shock resistances.



Advantages of Hetero-modulus Ceramic Reinforced Light Metal Alloys

Methods to increase mechanical properties



Short fiber reinforced　 complex

material

Particle reinforced　complex material

Continous fiber reinforced　 complex

material

Some methods to prepare foams and composite materials



Impregnation of the molten

metal

PoreMetal

• There are several methods to produce foams, cellular materials and low density, high porosity composites.

The main technological steps used by authors



• Selecting the ceramic raw materials and pore forming additives

• Forming and sintering the high porosity Al2O3 cellular ceramics

• Filtering the Al metal alloys into the Al2O3 cellular ceramic matrix of the required shapes

• Tempering and reactive resintering

Preparing high porosity Al2O3 cellular ceramics



• Selection of Al2O3 powder.• Selection the raw material additives.• Preparing the raw material (Al2O3) and the pore forming additives

(A,B,C,D,E,G) mix.• Shaping and forming the raw material (Al2O3) and the pore forming

additives (A,B,C,D,E,G) mix.• Sintering the formed raw material (Al2O3) with the pore forming

additives (A,B,C,D,E,G).• Examination the quality of the prepared Al2O3 ceramics as matrix

material for Al alloys.

Selection of Al2O3 powders and pore forming additives



Part ic le D iam eter (µ m .)

Volum e %

0

10

20

30

0

10

20

30

40

50

60

70

80

90

100

1.0 10.0 100.0 1000.0

I II III IVAl2O3 (g) 100 100 100 100

A (g) 12 12 12 12B (g) 10C (g) 10D (g) 10E (g) 2.5G (g) 6 6 6 6Water

(g)x x x x

Distribution of the particle size of the alumina



• Shaping and forming specimens from the raw material (Al2O3) and the pore forming additives (A,B,C,D,E,G) mix:

Forming the prepared raw material mix with pore forming additives



• Sintering curve of the specimens from the formed raw material (Al2O3) with the pore forming additives (A,B,C,D,E,G)

Sintering the formed specimens

0 10 20 300

200

400

600

800

1000

1200

1400

Time, /hourtTe

mpe

ratu

re,

/℃

T

1st step

2nd step

Natural Cooling

1st step

Heating rate: 50 ℃/hour

Heating temperature: 300 ℃

Keeping time: 2 hour

Atmosphere: Air

2nd step

1st Heating rate: 50 ℃/hour

2nd Heating rate: 100 ℃/hour

Heating temperature: 1350 ℃

Keeping time: 5 hour

Atmosphere: Air



Modelling the pore-forming process during sintering Al2O3 cellular ceramics

Liquid

Gas 　(Vapor)

Gas

Gas 　(Vapor)

From “Liquid and Solid” to “Gas (Vapor)”

From “Solid” to “Liquid”

: Liquid (Material G, Water)

: Solid (Additive materials B, C, D)

: Solid (Additive material E)



The achieved porosities of Al2O3 cellular ceramic material for matrix

Porosity of Alumina

III

III

IV

I

IIIII

IVI II III

IV

46

48

50

52

54

56

58

Poro

sity P

/%Ave.Max.Min.



The typical microstructures of the developed Al2O3 cellular ceramic matrix material



Filtering the Al metal alloys into the Al2O3 cellular ceramics

Argon gas

Al-alloy

Cellular Al2O3



Problems of wetting during filtering the Al metal alloys into the Al2O3 cellular ceramics

Material

Material

θ

Molten metal

Pressure less impregnation

method

Pore

Contact angle

PPressure

impregnation method



Typical microstructures of the developed low density Al2O3 reinforced high porosity Al alloys during not enough wetting

Al-alloy

Al2O3

Fe, Mn

Fe, Mn Fe

Fe

Al

Si



Typical microstructures of the developed low density Al2O3 reinforced high porosity Al alloys with extreme hardness



Surface hardness of the developed high porosity hetero-modulus Al alloy composites

HV10 hardness values measured on samples

Number of measure

HV10 hardness

1 12572 11783 12884 11235 11106 1231

Average 1198INSTRON Tukon 2100B hardness tester



Summary

• The authors successfully find at least one pore forming additive using which the wetting angle between Al2O3 matrix and Al-alloy could have considerably decreased.

• The developed new, cellular ceramics reinforced, low density Al-alloy composites have at least two, or more moduli of Young and have excellent ability to dissipate mechanical stresses.

• The developed by authors alumina reinforced high porosity Al-alloys have density less, than 1.3 g/cm3 and at 100 N loading force hardness higher than HV 1100.

Acknowledgement

The authors acknowledge to Igrex Engineering Service Ltd. for the financial and technical support of this research for several years and to young colleagues and PhD students of Department of Ceramic and Silicate Engineering at the University of Miskolc (Hungary) for laboratory tests and assistance.



Thank you very much for your time and kind attention !

http://keramia.uni-miskolc.hu http://www.szte.org.hu/folyoirat

László A. GömzeUniversity of Miskolc

3515, Miskolc, [email protected]

Phone: +36 30 7462714

Liudmila N. GömzeIgrex Ltd.

3459, Igrici, [email protected]

Phone: +36 30 7462713



Alumina Reinforced High Porosity Al-alloys with Extreme Hardness

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