Background Mg AZ31B sheet alloy has advantages of low density, high strength and high stiffness. However, it has limited formability at room temperature, and unknown behavior at complex forming conditions, especially in the thermoforming process. The objective of this research is: 1) Design and optimize test devices for elevated-temperature tension / compression (T / C) of sheet metal alloys 2) Measure T / C plastic hardening curves for Mg AZ31B sheet 3) Develop constitutive laws for Mg AZ31B sheet alloys (0.1/s-10-4/s, 150oC-300oC) 4) Simulate thermo-assistant deep drawing of Mg AZ31B, enhancing formability using non-isothermal heating strategies 1

Sheet Tension / Compression Test Room Temperature G=36.8mm B=50.8mm W=15.2mm L>3mm Side Force Mg AZ31B, O-temper, 3.2mm Laser extensometer Boger et al., Int. J. Plast., 2005 Lou et al., Int. J. Plast., 2007 2

Sheet Tension / Compression Test Elevated Temperature 3

Sheet Tension / Compression Test Elevated Temperature 4

Constitutive Equations, 150oC-300oC: Mg AZ31B 1mm sheet M1 <7MPa>: M2opt <4MPa>: <0.03> <0.98> <0.49> 5

Thermo Deep Drawing Axisymmetric Uniform Temperature: 150oC-300oC: Punch: t = 1.0 mm R = 60 mm Blank holder Die R = 5 mm 25 mm Uniform Temperature: 150oC-300oC: Axisymmetric Material Model: M2opt Friction coeffcient = 0.08 Fix the positions of blank holder and die Finer Mesh in the corner of punch and die Velocity of punch = 10, 1, and 0.1 mm/s hto air = 20 W/m2K 300oC 6

Thermo Deep Drawing R=60mm, Punch speed = 1mm/s Failure criteria: thickness strain = -0.2 150oC-300oC 50 mm 150oC 14 mm Necking LDR = Di/Df (Depth) 10mm/s 1mm/s 0.1mm/s 150oC 1.9 (38mm) 1.9 (37mm) 200oC 250oC 1.8 (36mm) 300oC 1.8 (35mm) 150oC-200oC 2.3 (58mm) 2.2 (49mm) 150oC-250oC 2.4 (63mm) 2.6 (72mm) 2.6 (73mm) 150oC-300oC 3.2 (121mm) 3.2 (123mm) 3.3 (125mm) *Diameter of finished cup: Df = 55.2mm 7

Conclusions Develop high-temperature T/C device Temperature range: RT - 450oC DT (Gage Length) < 8oC Heating time = 10 minutes for 250oC High Temperature T/C testing of Mg AZ31B sheet: Inflected flow (twinning) disappears between 130oC - 140oC Constitutive equations for Mg AZ31B sheet: Experiments, numerical fitting and FEA verification 150oC - 300oC, 0.1-10-4/s, standard deviation = 4MPa Thermo-assistant deep drawing: Non-isothermal heating improve the LDR from 1.9 to 3.3 8

Mg AZ31B Sheet Formability: Experiment and Simulation K. Piao and R. H. Wagoner Department of Materials Science and Engineering, The Ohio State University