University of Illinois at Urbana-Champaign Thermo- -Mechanical Fatigue of Cast Mechanical Fatigue of Cast Thermo 319 Aluminum Alloys 319 Aluminum Alloys Huseyin Sehitoglu, 1 Carlos C. Engler-Pinto Jr. 2 , Hans J. Maier 3 ,Tracy J. Foglesong 4 1 University of Illinois at Urbana- Champaign, USA, 2 Ford Motor Company, Dearborn, 3 Universität- GH Paderborn, Germany, 4 Exxon , Houston Research Supported by Ford Motor Company Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Outline Outline • Use of Aluminum Alloys in engine blocks and cylinder heads • Thermo-Mechanical Fatigue Results • Summary • Modeling Studies (Precipitation hardened aluminum alloys) Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Percentage of Vehicles with Aluminum Percentage of Vehicles with Aluminum Engine Blocks and Heads (*) Engine Blocks and Heads (*) 1994 2000 2005 Heads Passenger cars 78% 85% 95% Light trucks 20% 40% 60% Blocks Passenger cars 13% 30% 50% Light trucks 5% 10% 20% (*) Delphi VIII Study, 1996 Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Advantages of cast aluminum Advantages of cast aluminum • Lightweight – V-8 Engine Block: 150 lbs Cast Iron vs. 68 lbs Aluminum • Cast into complex shapes • Increased thermal conductivity Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Practical Application Practical Application • Cylinder Heads Spark Plug Inlet Valve Exhaust Valve Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Al319- -T7B T7B Al319 • Nominal Composition in weight percentage Al Si Cu Mg Mn Fe Zn Ti Cr Bal. 7.2- 3.3- 0.25- 0.20- * 0.25 0.25 0.05 7.7 3.7 0.35 0.30 max max max – (*) WAP319: max 0.4% Fe - EAP319: max 0.8% Fe • Thermal treatment – solutionizing at 495°C for 8 hours followed by precipitating at 260°C for 4 hours) Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Thermo- -Mechanical Fatigue Cycles Mechanical Fatigue Cycles Thermo • Simultaneously changing strain and 300 temperature (T) T (¡C) 200 • In-Phase : max-strain at max-T • Out-of-Phase : max-strain at min-T 100 1 1 IP IP ε mech (%) ε mech (%) 0 0 OP OP -1 -1 0 2 4 6 100 200 300 time (min) T (¡C) Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Thermo- -Mechanical Fatigue Mechanical Fatigue Thermo • Fatigue of materials subjected to simultaneously changing temperature and strain. Temp. TMF OP TMF IP T max • ε tot = ε th + ε mech • Terminology ε max ε min – in-phase Mech. Strain – out-of-phase T min Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign TMF Testing TMF Testing Micro-Computer ε ε ε ε vs. t ε ε ε ε T vs. t T F load cell pyrometer Induction extensometer Heating Hydraulic Testing Machine Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Experimental Procedures Experimental Procedures • Isothermal LCF – 20°C, 150°C, 250°C and 300°C – 2 × 10 -1 s -1 , 4 × 10 -3 s -1 and 5 × 10 -5 s -1 • Thermo-Mechanical Fatigue – 100–300°C — 5 × 10 -5 s -1 Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign TMF Loops TMF Loops 200 1 Cycle Out-of-Phase In-Phase ∆ε m = 0.6% 200 ∆ε m = 0.54% 100 1220 Stress (MPa) 100¡C 0 100¡C 300¡C 200 -100 20 300¡C N f = 2460 N f = 390 1 -200 -0.4 -0.2 0.0 0.2 0.4 -0.4 -0.2 0.0 0.2 0.4 Mechanical Strain (%) Mechanical Strain (%) Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign TMF OP 100- -300°C 1.0% 300°C 1.0% TMF OP 100 200 100°C 100 Stress (MPa) 200°C 0 -100 300°C STRESS1-2fea Stress1-2 STRESS300fea Stress300 -200 -3 -6x10 -4 -2 0 2 4 6 Strain Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Fatigue Life Criterion Fatigue Life Criterion 120 Maximum Stress (MPa) 80 50% Load Drop 40 LCF - 250°C - 0.3% - 0.5 hz WAP319-T7B 0 0 5000 N f Number of Cycles Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Precipitate Precipitate Coarsening Coarsening 80 Yield Strength (MPa) Initial 60 40 20 Exposure at 300°C 0 45000 cycles / ~25 hours (300°C, ∆ε m = 0.2%). 0 20 40 60 80 100 120 time (h) Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign TMF Loops TMF Loops IP Inelastic Strain (%) 0.6 0.4 0.2 0.0 -0.2 -0.4 200 -200 100¡C OP IP OP Stress (MPa) IP Stress (MPa) 100 -100 0 0 300¡C -100 100 -0.6 -0.4 -0.2 0.0 0.2 0.4 OP Inelastic Strain (%) Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign TMF – – Peak Stresses Peak Stresses TMF 300 OP IP 250 σ max - σ min 200 100¡C Stress (MPa) 150 300¡C 100 50 2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 2 0.1 1 Inelastic Strain Range (%) Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign TMF – – Stress Range Evolution Stress Range Evolution TMF 350 EAP319-T7B TMF OP TMF IP 300 Initial Behavior Stress Range (MPa) 250 IP N f /2 200 OP N f /2 150 100 50 0 500 1000 1500 2000 2500 Number of Cycles Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Cyclic Stress- -Strain Curves Strain Curves Cyclic Stress 400 WAP319 WAP319 EAP319 TMF OP TMF OP 350 TMF IP TMF IP 300¡C 0.5 hz -5 s -1 Stress Range (MPa) 300 300¡C 5x10 250 200 EAP319 150 2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 2 0.0001 0.001 0.01 Inelastic Strain Range Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign TMF Life TMF Life 5 Room 4 150¡C 40 hz Temperature 3 250¡C 40 hz Mechanical Strain Range 250¡C 0.5 hz 2 -5 s -1 250¡C 5x10 -5 s -1 300¡C 5x10 0.01 300¡C 0.5 hz TMF OP 6 TMF IP 5 4 3 2 EAP319-T7B 0.001 1 2 3 4 5 6 7 8 10 10 10 10 10 10 10 10 Cycles to Failure Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign TMF Life TMF Life 400 TMF IP Room 350 -5 s -1 Temperature 5x10 300 250¡C -3 s -1 250 2x10 Stress Range (MPa) 200 150 150¡C 100 -5 s -1 TMF OP 5x10 -1 s -1 2x10 -3 s -1 300¡C 2x10 -5 s -1 EAP319-T7B 300¡C 5x10 50 1 2 3 4 5 6 7 8 10 10 10 10 10 10 10 10 Cycles to Failure Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign TMF Life TMF Life OP + LCF 2 0.01 Inelastic Strain Range 8 6 IP 4 2 EAP319 250¡C 0.5 hz 0.001 -5 s -1 250¡C 5x10 8 6 300¡C 0.5 hz -5 s 4 -1 300¡C 5x10 WAP319 TMF OP TMF OP 2 TMF IP TMF IP 0.0001 1 2 3 4 5 10 10 10 10 10 Cycles to Failure Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign EAP319- -T7B T7B EAP319 TMF- -OP OP TMF 100– –300°C 300°C 100 ∆ε m ∆ε =0.6% m =0.6% N f =2460 c. N f =2460 c. Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign EAP319- -T7B T7B EAP319 TMF- -IP IP TMF 100– –300°C 300°C 100 ∆ε m ∆ε =0.54% m =0.54% N f =390 c. N f =390 c. Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign 5 4 WAP EAP Prediction 0 = 70 µ m a TMF-IP 3 TMF-OP 2 300 µ m Mehanical Strain Range 0.01 9 8 7 6 5 4 3 2 2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 1 2 3 4 10 10 10 10 N f Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Summary Summary 1. TMF stress-strain behavior is identical for both IP and OP loading conditions. TMF-IP lives are shorter than TMF-OP (based on the mechanical or inelastic strain range) lives. 2. Creep damage dominates for TMF-IP loading and in the high strain range regime. 3. The secondary alloy (EAP319) is softer than the primary alloy (WAP319), but TMF lives are very similar. Department of Mechanical and Industrial Engineering
University of Illinois at Urbana-Champaign Aluminum- -Copper Alloys Copper Alloys Aluminum • Precipitate-dislocation interactions – Anisotropy on plastic flow behavior (Hosford & Zeisloft ‘72, Bate et al. ‘81, Barlat & Liu ‘98, Choi & Barlat ‘99) – Bauschinger effect (Abel & Ham ‘66, Moan & Embury ‘79, Wilson ‘65) Coherent particles - GP zones and θ '' (Price and Kelly ‘64) • – Higher yield stress than Al shearing of particles – Comparable work hardening rates and deformation to Al Semi-coherent - θ ' ( P & K ‘64, Russell & Ashby ‘70) • – High yield stress and high work hardening rates Incoherent particles - θ ( P & K ‘64, R & A ‘70) • – Low initial yield stress – Highest rates of work hardening Department of Mechanical and Industrial Engineering
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