Composite Materials
description
Transcript of Composite Materials
Composite Materials
Resistance Welding
Lesson ObjectivesWhen you finish this lesson you will understand:•
Learning Activities1. View Slides; 2. Read Notes, 3. Listen to lecture4. Do on-line workbook
Keywords
Matrix Materials
Magnesium• Lowest density (37% lighter than aluminum) • Aerospace applications• Creeps at low temp• Relatively low strength• Prone to variety of corrosion problems
Aluminum• Easy to process, inexpensive• Density only 35% of Steel• Can be alloyed to fairly high strengths• 57% stiffer than Magnesium• Excellent corrosion resistance• Most widely used material
Matrix Materials
Titanium• Twice as strong as aerospace aluminum• 65% heavier than aluminum, but 65% stiffer• Temp & corrosion resistant = use in demanding environments
Copper, Iron, Nickel, Tungsten• Special use alloys
• Electronic Circuits• Metal forming dies• Jet engines• Military applications
Reinforcements
Ceramics• Silicon Carbide (SiC)• Aluminum Oxide (Al2O3)• Titanium Carbide (TiC)• Boron Carbide (B4C)
Other• Graphite (C)• Titanium Diboride (TiB2)
Metal Filaments• Boron• Steel• Tungsten
Choice of matrix and reinforcement depends on:• Desired properties of composite• Compatibility between matrix and reinforcement• MMC Processing route
orcementinfrer
matrixm
compositec
fractionvolumeV
consideredpropertyX
Where
VXVXX rrmmc
Rule of Mixtures
Designation for MMC
Matrix + Reinforcement / Volume % Form
Matrix = metal or alloy designation of matrixReinforcement = chemical formula of reinforcementVolume % = Volume percent without the % signForm = Form of the reinforcement
• f, fiber or filament• c, chopped fiber• w, whisker• p, particulate
Example: 6061 + SiC/20w
Welding Handbook, AWS
Particulate Composite
Short-Fiber Composite
Long-Fiber Composite Laminated Composite
Manufacturing ProcessesWelding Handbook, AWS
Processing Methods
Solid StateSemi-solidLiquid
Solid State Processing
Bonding of continuous fibers between metal foils to make panels• Aerospace Applications• Ti/Sic; Al/B
Laminated Composite
Powder Metallurgy• Mix particles of matrix with reinforcement• Vacuum hot press (near solidus)• Extrude or roll• Al/B4C; Al/SiC
Semi-Solid Processing
Spray Deposition
Chilled Plate
MMC Build UpMMC Build Up
Flame Spray MatrixFlame Spray Matrix
Flame Spray Reinforcement
………..
Rheocasting• Mix reinforcement into matrix held between solidus and liquidus
TEMP
COMP
x
Liquid Processing
Infiltration• Interfacial reactions can be a problem
Applications - From Ukraine
Krivov, Optimization of design-production…,Welding in the World, Nov-Dec 1994
Applications
Krivov, Optimization of design-production…,Welding in the World, Nov-Dec 1994
Krivov, Optimization of design-production…,Welding in the World, Nov-Dec 1994
Welding Handbook, AWS
Detrimental Weld Pool Chemical Reactions
]l[Al2]s[OMgAl3]s[OAl4]Al[Mg3
)TiAlAlTi](l[Al]Al[Si]s[TiC]s[SiC]l[Al3]Al[Ti5
]Al[Si3]s[CAl]s[SiC3]l[Al4
4232l
3ll
l34
[l] indicates liquid phase[s] indicates solid phase[All] indicates in solution with liquid aluminum
ResistanceWelding
ArcWelding
Time-Temp Effect of Chem Reaction
Welding Handbook, AWS
Capacitor Discharge• Stud Welding• Solid State• Fusion Weld• Brazing
Capacitor Discharge Stud Welding
MMC Materials Welded• 6061, 2024, 6061/SiC/40p, 6061/SiC/48f, 6061/B4C/30p,
AZ61/B4C/40p• Studs = 0.25 in; Sheet=0.13 in• Time = 0.4 ms• Solidification rate = 106 C/s
Welding Handbook, AWS
Stud Welding
Welding Handbook, AWS
Welding Handbook, AWS
Capacitor Discharge - Solid State Welding• Ti-6Al-4V/SiC Sheets• Ti-6Al-4V/SCS-6
Diffusion (solid state) BondNo Melting
Failure Occurred Upon Loading Remote from Weld Interface
Baeslack & Froes, Joining Similar & Dissimilar……,JOM March 1995
SCS-6 is a complex fiber with SiC vapor deposited onto a graphite carbon core
Increase in Welding Current (Voltage) Causes ChangeFrom Solid State to Fusion Weld
Cox et al, Capacitor Discharge RSW of SiC Fiber…Welding Journal, Oct 1993
Capacitor Discharge Solid State WeldNo liquid - Weld Strength 80% of Monolithic
SCS-6 Fiber
Cox et al, Capacitor Discharge RSW of SiC Fiber…Welding Journal, Oct 1993
Solid State Weld with no Fiber degradation
Cox et al, Capacitor Discharge RSW of SiC Fiber…Welding Journal, Oct 1993
Capacitor Discharge - Fusion Welding
Partial Melting Fusion Weld
Cox et al, Capacitor Discharge RSW of SiC Fiber…Welding Journal, Oct 1993
Solidified Liquid around fiber, Property degradation
Cox et al, Capacitor Discharge RSW of SiC Fiber…Welding Journal, Oct 1993
Al-7Zn/CBAlSi-4BrazingFoil
Low force = expulsion> 400 lb = fiber packing at weld center (see next slide)
Spot Brazing Continuous C Fiber MMC
Welding Handbook, AWSBrazing
Spot Brazing Continuous SiC Fiber MMC
Ti-22Al-23Nb/SiC
Ti-Cu-NiBraze Foil
Baeslack & Froes, Joining Similar & Dissimilar……,JOM March 1995
Baeslack & Froes, Joining Similar & Dissimilar……,JOM March 1995
ResistanceWelding
ArcWelding
Time-Temp Effect of Chem Reaction
Welding Handbook, AWS
Resistance Spot Welding• Solid State• With Melting/Solidification
Spot Welding
Welding Handbook, AWS
Adjusting Welding ForceWelding TimeTo Avoid FiberCrushing inAl/B MMC
Welding Handbook, AWS
(Continuous Fiber)
Aluminum/Boron Continuous Fiber
Hersh, Resistance Spot Weld MMC,Welding Journal, June 1970
Aluminum/Boron Continuous Fiber
Hersh, Resistance Spot Weld MMC,Welding Journal, June 1970
Aluminum/Boron Continuous Fiber
Hersh, Resistance Spot Weld MMC,Welding Journal, June 1970
Aluminum/Boron Continuous Fiber
Hersh, Resistance Spot Weld MMC,Welding Journal, June 1970
Aluminum/Boron Continuous Fiber
Hersh, Resistance Spot Weld MMC,Welding Journal, June 1970
Spot Welding Discontinuous Fibers
Segregation of reinforcement (see next slide)
Welding Handbook, AWS