Hot deformation behavior and microstructure evolution of TC17 alloy with lamellar and β treated starting microstructures during stepped strain rate compression

Abstract

The hot deformation behavior and microstructure evolution of TC17 alloy with lamellar and β treated starting microstructures during stepped strain rate (20 s−1 + 0.1 s−1, 20 s−1 + 1 s−1 and 20 s−1 + 10 s−1) hot compression (840 °C) were investigated in this study. The high strain rate of 20 s−1 was applied from beginning to 40 % compression and was changed to 0.1 s−1, 1 s−1 and 10 s−1 respectively during 40–60 % range. Results show that the alloy with two microstructures exhibited similar flow curves during the whole strain range while the lamellar sample displays more evident flow softening during second compression stage with strain rate of 10 s−1. The obvious adiabatic shearing band (ASB) with coarsen β grains inside was formed in the 40 % compressed lamellar alloy and the high dislocation density was featured at grain boundaries. The stability of β phase in ASB was lower than that of the β treated alloy with same compression mainly due to the occurrence of α→β dynamic transformed (DT). Both the microstructure evolution of lamellar/β treated alloys after 60 % compression was dominated by dynamic recovery (DRV) associated grain decomposition mechanism except the dramatic dynamic recrystallization (DRX) of lamellar alloy with stepped strain rate of 1 s−1. The dot/lath-like α precipitation was achieved in both the 60 % compressed alloys and it was promoted by higher stepped strain rate.