Microstructure and mechanical properties of TA15 alloy after thermomechanical processing

Thermo-mechanical processing (TMP) is one of effective techniques for fabricating of bulk ultrafine grained materials, which employs plastic deformation and heat treatment. In this paper, three different thermo-mechanical processing routes were used. The optimum processing route is that the alloy was forged in beta and alpha + beta phase field respectively, and the immediate water-quenching was conducted after forging. The equiaxed and fine-grained TA15 alloy with mean grain size of 2 mu m was successfully fabricated. Based on observation and analysis of microstructure evolution during thermo-mechanical processing, the main mechanism of grain refinement is continuous dynamic recrystallization, and the acicular marstensite alpha, phase resulted from fast waterquenching after forging in beta phase field is contributed to further grain refinement in alpha + beta phase field. Compared with the as-received material, it is found that the mechanical properties of the fine-grained TA15 alloy at room and high temperatures were enhanced significantly. Additionally, according to SEM analysis, the fine-grained TA15 alloy shows a typically ductile fracture mode, but the fracture surface of as-received material is of quasicleavage fracture character.