Metal Matrix Composites (MMCs)

Metal Matrix Composites (MMCs)
Properties, Applications & Machining
Olivier Beffort
EMPA, Swiss Federal Laboratories for Materials Research and Testing
Dept. Materials Technology
Feuerwerkerstrasse 39
CH-3602 Thun
olivier.beffort@empa.ch
www.empathun.ch
6. Internationales IWF-Kolloquium
18/19.04.2002, Egerkingen, CH
structure of the talk
• introduction to MMCs
• typical properties of MMCs
• applications of MMCs
• machining of MMCs
• outlook - trends in R&D, market forecasts
ca. 1975
sources: NASA & AFRL
Space Shuttle - main cargo bay struts
material: MMC - 6061/B/50f
total weight saving: 145 kg (-44% vs Al)
materials costs: > 1’000 US-$ / kg
ca. 1999
VW-Lupo (Tdi) - rear brake drums
material: MMC - A359/SiC/20p
weight of drum: 1.55 kg
materials costs: < 5 US-$ / kg
source: VW
MMCs - materials with tailored properties ...
... by combination of metals and ceramics
specific properties of metals and ceramics
metals.........
Al
Mg
(Ti)
toughness
electrical & thermal conductivity
heat resistance, "environmental stability"
processability
ceramics..... Young’s Modulus, hardness, wear resistance
SiC
strength
Al2O3
low coefficient of thermal expansion
(shape of ceramic: fibres, particles)
C, B4C
Types of reinforcement for MMCs
particles and "foams"
particles (ceramics, carbon, ...)
volume fraction: 5 - 75%
size: 0.1 - 500 µm
"foams" (ceramics, graphite, ...)
cearmic volume fraction: 20 - 90%
pore size: 50 nm - 1 mm
Types of reinforcement for MMCs
fibres
100 Pm
short fibres (ceramics, carbon, ...)
volume fraction: 10 - 30%
size: ∅: 1 - 6 µm, L: 10-500 µm
cont. fibres (ceramics, carbon, ...)
volume fraction: 40 - 70%
size: ∅: 6-150 µm, L: ∞
structure of the talk
• introduction to MMCs
• typical properties of MMCs
• applications of MMCs
• machining of MMCs
• outlook - trends in R&D, market forecasts
particle reinforced MMCs
(PRM) vp: 5-75 %
• isotropic properties
• high wear resistance
• low density ............................................... 2.6 - 3.1 g/cm3
• high elastic modulus ............................... 90 - 300 GPa
• high strength ............................................ 300 - 1000 MPa
• good thermal conductivity ...................... 120 - 200 W/mK
• low coeff. of thermal expansion (CTE) ... 7 - 20 10-6/K
fibre reinforced MMCs
(FRM) vf: 10-70 %
• anisotropic properties
• low density ........................ 1.8 - 3.2 g/cm3
• high strength ..................... 500 - 2000 MPa
• high elastic modulus ....... 120 Ÿ 300 GPa
• low CTE ............................. 0 - 10 10-6/K
• elevated temperature resistance (strength, fatigue, creep)
structure of the talk
• introduction to MMCs
•typical properties of MMCs
• applications of MMCs
• machining of MMCs
• outlook - trends in R&D, market forecasts
MMC brake discs & drums applications
MMC - type: AlSiMg/SiC/20-30p
trains (ICE)
VW Lupo
Toyota RAV-4EV
Plymouth Prowler
GM EV-1, Precept, Impact
Ford Prodigy
Lotus Elise (1st series)
race carts (various)
....
source: Lotus Cars Ltd.
source:
Knorr Bremse
automotive applications - engine
Toyota Celica
source: Kolbenschmidt
source: Honda
cylinder blocks and pistons
(local reinforcement for wear and creep resist.)
material: AlSi + short fibres and/or particles
Porsche 911, Boxster
Toyota Celica
Honda Prelude, NSX, ...?
power conversion / electr. packaging applications
IGBT-modules (Insulated Gate Bipolar Transistor)
"thermal management applications"
50 mm
MMC - type:
AlSi/SiC/70p
CTE: 7-9 10-6/K
max rated voltage: VCE = 3300 V
Nominal current IC = 1200 A
source: EUPEC
structure of an IGBT-module
Bond Wire
CTE [ppm/K]
Solder
Si
Si
Si
Al2O3 or AlN Insulation
Cu or Al Heats Spreader
Grease
Heat
source: ABB Semiconductors
Cooler
Copper
4.2
6.7 / 4.4
17 / 23.5
17 / 23.5
further MMC applications:
• racing, sports, leisure
• cylinder liners, push rods, brake calipers, ...
• spikes for racing shoes & tires, golf clubs, bicycle frames, ....
• aerospace applications
• Space Shuttle - main cargo bay struts
• Boeing 777 / Pratt & Whitney - fan exit guide vanes
• Eurocopter - blade sleeves
• F16 - ventral fins, fuel access door covers
• thermal and electric transportation
• heat sinks, electronic packaging, ....
• cooking ware
• power transmission cables (electric conductors)
• robotics, linear technology, weaving machines, ........
• military applications, .....
structure of the talk
• introduction to MMCs
• typical properties of MMCs
• applications of MMCs in transportation
• machining of MMCs
• outlook - trends in R&D, market forecasts
frequent statements concerning MMC machining
• MMC cannot be machined.................................... no !
• conventional tools cannot be used for MMCs.... yes !
• diamond tools are a must for MMC machining... yes !
• MMCs cannot be machined cost effectively........ no !
• MMCs are difficult to machine............................. yes !
why are MMCs difficult to machine ?
because of the relative hardness of the reinforcing materials
tool wear mechanisms occuring during
MMC machining
• abrasion due to hardness of reinforcement
• impact fatigue, break-outs
tools suitable for MMC machining
• PCD or CVD diamond tools are the best
• do not use CBN tools
• do not use HSS tools (not even coated ones)
• do not use un-coated WC/Co tools
influence of tool material on tool wear
0.6
PKD, vc 500 m/min
WC/TiN, vc 150 m/min
flank wear vB, [mm]
0.5
0.4
0.3
MMC material:
vc:
feed:
DOC:
operation:
0.2
0.1
0
0
2
4
6
8
time, [min]
source: Duralcan machining guidelines
10
12
14
Al/Al2O3/20p
500 m/min
0.4 mm/rev
1.5 mm
turning
parameters affecting machinability
machining performance or machinability is
defined in terms of tool life, material removal rate
or surface quality of machined part
the influencing parameters are :
• MMC material - particle type, vol. fract, temper, ...
• tool - type and grade
• machining parameters - feed, speed, DOC
influence of MMC - reinforcement
the following characteristics decrease tool life:
• increasing particle volume fraction
• increasing particle size
• increasing particle hardness
• increasing aspect ratio of particles
influence of MMC - quality & temper
the following characteristics decrease tool life:
• defects (porosity, inclusions, segregations, ...)
• age hardening (peak aged condition T6)
influence of tool - type and grade
controversy - PCD or CVD diamond ???
for PCD tools, influence of diamond grain size:
• three common PCD grades: 2, 10 and 25 Pm
• 25 Pm best wear resistance; for roughing
• 2 Pm best edge quality for finishing
roughing and finishing operations
for roughing coarse grained PCD (or CVD)
and the most possible aggressive feed rate
and depth of cut are recommended: best
tool life performance
for finishing fine grained PCD or CVD and
moderate feed rate and depth of cut are
recommended: best surface finish quality
influence of machining parameters
the following characteristics increase tool life:
• high feed rate (< 0,5 mm/rev)
• high depth of cut (< 5 mm)
• medium cutting speed (300-500 m/min)
influence of feed rate on material removal
10000
volume removed (MMC), [cm3]
9000
8000
MMC material:
tool material:
vc :
DOC:
operation:
7000
Duralcan F3S.20S
PCD
300m/min
0.5 mm
turning (stop @ 0.25 vB mm)
6000
5000
4000
3000
2000
1000
0
0,1
0,2
feed rate, [mm/rev]
source: Duralcan machining guidelines
0,4
machining operations
• turning
feasible, PCD or CVD diamond tools
• milling
feasible, PCD or CVD diamond tools
• drilling
difficult, PCD or CVD diamond tools
• tapping
critical, CVD tools in development stage
tap forming is an alternative to tap cutting
• sawing
feasible, WC- or PCD tipped blades
• grinding feasible, diamond grinding
MMC machining cost issues - example
US-study concerning machining costs of brake rotors
cast iron rotor
parts per day:
1900
tool costs, $/day 402
MMC rotor
3131
2048
cost savings
0.15 $/rotor
PCD - tools
reference
CVD - tools
tool costs, $/day
568.75
MMC drilling cost issues - sp3 examples
Ford Motors Co.
drilling 6.8 mm diam. holes 1.00´´ deep into Al/SiC/20p
drilling conditions: speed:1350 rpm, feed: 0.0075 ipr
WC/Co-drills: 1 - 2 holes per drill ⇒ $9 - $18 /hole
CVD-drills: 330 holes per drill ⇒ $0.40 /hole
MSE
drilling 0.25´´ diam. holes into Al/SiC/20-48p
WC/Co-drills: < 1 hole per drill
CVD-drills: >200 holes per drill ⇒ $0.52 /hole
(cost of CVD drill: $115/drill
machining - conclusions
• recommended machining
guidelines should be respected
• only diamond tools should be
used for machining MMCs
• an MMC with an ultrafine and low hardness
reinforcement is preferred
• except tapping, most common machining
operations are possible
structure of the talk
• introduction to MMCs
• typical properties of MMCs
• applications of MMCs in transportation
• machining of MMCs
• outlook - trends in R&D, market forecasts
materials and process development - future
materials development
• selectively reinforced structures
• functional, adaptive materials
• graded materials
process technology
• "reactive" in-situ generation of MMCs
• near net shape MMC processing technologies
• low cost MMC processing technologies
machining
• adapted tools (materials, coatings, geometries, ...) and lubricants
• optimised machining parameters
• alternative machining processes
MMC market forecasts 1999-2004
3500
3400
annual MMC world market, [t]
3000
market share: 62.2 %
market share: 70.3 %
AAGR: + 16.3 %
1999
2004
2500
1999: 2.5 Mio kg, 103 Mio US-$
2004: 4.9 Mio kg, 173 Mio US-$
2000
1500
1600
market share: 26.5 %
market share: 21.9 %
AAGR: + 9.8 %
1000
1000
668
500
market share: 5.4 % market share: 5.9 %
market share: 3.3 % market share: 4.5 %
AAGR: + 7.7 %
AAGR: + 3.3 %
137
161
152
220
0
ground
transportation
source: BCC, USA
thermal
management
aerospace /
defense
industrial /
recreational equip.
http://www.empathun.ch
http://mmc-assess.tuwien.ac.at