Effects of the width of secondary α phase on Dynamic Mechanical Properties and Sensitivity of Adiabatic Shear Banding in bimodal microstructures of TC4 alloy

Abstract:

In this paper, the dynamic mechanical properties and sensitivity of adiabatic shear banding of TC4 alloy having bimodal microstructures were invesgated using Split Hopkinson Bar.The bimodal microstructures with different width of secondary α phase (α_s) were obtained via different heat treatment. The results showed that the width of α_s increased with the decreasing of cooling rate. Under dynamic compression experiments, the dynamic strength decreased as the width of α_s increased; while the dynamic strain exhibited an opposite trend. Under forced shearing experiments, the sensitivity of adiabatic shear banding decreased as the width of α_s increased. Besides, the sensitivity of adiabatic shear banding increased for the same microstructure with the increasing of impact velocity. Combined with the effects of volumn fraction of transformed β and width of α_s on dynamic mechanical properties and sensitivity of adiabatic shear banding of TC4 alloy, the bimodal microstructure obtained by the heat treatment,980℃/1h/A+550℃/4h/A, had good high strength and low sensitivity of adiabatic shear banding matching. The optimal bimodal microstructure had a volumn fraction of transformed β matrix of 80.7% and the width of α_s plates was 1.74 μm.

Key words:bimodal microstructure of TC4 alloy, secondary α phase, dynamic mechanical properties, sensitivity of adiabatic shear banding