Tensile property and fracture behavior of hot-rolled CoTi intermetallic compound

Abstract

B2-type CoTi intermetallic compound was arc-melted, hot-rolled at 1273 K and then recrystallized at 1323 K. Tensile tests were carried out at temperatures from room temperature to 1223 K. Tensile behavior and fracture mode of CoTi were divided into three regions depending on temperature. From room temperature to ∼773 K, almost no plastic deformation was observed. In this region, fracture surfaces showed a mixed mode of quasi-cleavage and intergranular fracture. Above 773 K, a considerable necking began to occur, and tensile elongation increased with increasing temperature, accompanied by a brittle quasi-cleavage fracture. From 1073 to 1223 K, ∼50% tensile elongation took place, accompanied by almost 100% reduction in area. At this temperature region, a chisel edge type fracture took place. The brittle–ductile transition temperature (BDTT) of CoTi was defined as ∼800 K under the condition used in the present study. Also, the influence of thermal vacancies on mechanical properties of CoTi was briefly discussed.