Hot deformation behavior and constitutive model of TC18 alloy during compression

The hot deformation behavior of TC18 alloy at strain rates ranging from 1 × 10^-4 to 1 × 10^-2 s^-1 and temperatures ranging from 25 to 800 °C was studied using a WDW-300 electronic universal testing machine. The relationships between true stress and true strain show that flow stress decreases with the increase of temperature and increases as strain rate increases. The effect of strain rate on the flow stress becomes pronounced at higher temperatures. At room temperature, the river pattern characteristic of brittle fracture and the dimple pattern typical of ductile fracture are found to exist in different regions of fracture surfaces of the samples. An improved constitutive relationship is proposed to accurately describe the flow stress of TC18 by considering the effect of strain. And a microscopic model is also deduced which can link the physical mechanisms to the macroscopic experimental results. A good agreement is obtained between the predictions of the microscopic model and the results of the macroscopic experiment.