Effect of Strain Hardening and Aging Processes on Microstructure Evolution, Tensile and Fatigue Properties of Cast Ti-6Al-2Sn-2Zr-2Mo-1.5Cr-2Nb-0.1Si Alloy

Abstract: The effect of strain hardening and aging processes on microstructure, tensile and fatigue properties was investigated on cast TC21 samples with a chemical composition of Ti-6.1Al-2.96Mo-2.11Nb-1.98Sn-2.05Zr-1.44Cr-0.1Si. Plastic deformation (strain hardening) was applied on swaged samples at room temperature with 2%, 3% and 4% strain. By applying aging process at 575°C for 4 hr, secondary α-platelets were precipitated in the transformed β-phase. Maximum hardness (HV440) was achieved for 4%def. + aged samples. However, minimum hardness (HV323) was recorded for aged samples. Maximum ultimate tensile strength (1311MPa) and elongation (14%) were obtained for 4% def. + aged samples due to presence of high amount of dislocation density as well as precipitation of secondary α-platelets in the residual β-phase. Minimum ultimate tensile strength (1020MPa) and elongation (3%) were reported for as-cast samples. Theoretical study using ANSYS software program was carried out for estimating fatigue limits for investigated samples. For validating the theoretical results, experimental test was done using rotating bending fatigue testing machine on three selected conditions of swaged, 2%def. + aged and 4%def. + aged. Maximum estimated fatigue strength of 775 MPa was obtained for 4%def. + aged samples, and the experimental one was 755 MPa. Hence, the difference between estimated and experimental fatigue limits for 4%def. + aged samples was less than of 3%. Graphical Abstract: [Figure not available: see fulltext.] © 2021, American Foundry Society.