Mechanical response and microcrack formation in a fine-grained duplex TiAl at different strain rates and temperatures

摘要

Compressive behavior of this alloy was studied at strain rates of 0. 001 and 2000 sec(sup -1) and temperatures from -196 C to 1200 C. Temperature dependence of yield stress was found to depend on strain rate: At the quasi-static strain rate, 0.001 sec(sup -1), the yield stress decreases with temperature with a plateau between 200 and 800 C. At the high strain rate, 2000 sec(sup -1), the yield stress exhibits a positive temperature dependence above 600 C. Strain hardening rate decreases dramatically with temperature in the very low and high temperature regions with a plateau at intermediate temperatures for both strain rates. As the strain rate increases, the strain hardening rate plateaus extended to higher temperatures. The strain rate sensitivity increases slightly with temperature (but less than 0.1) for strain rates above 0.001 sec(sup -1). However, at a strain rate of 0.001 sec(sup -1), there is a dramatic increase in the strain rate sensitivity with temperature; above 1100 C, the rate sensitivity becomes much larger. Microcracks occurring in grain interiors and at grain boundaries were observed at all strain rates and temperatures. Formation and distribution of microcracks were found to vary depending on strain rate and deformation temperature.