Microstructure and mechanical properties of TA15 alloy after thermo-mechanical processing

Abstract

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 β and α+β 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 µm 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 α′ phase resulted from fast water-quenching after forging in β phase field is contributed to further grain refinement in α+β 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 quasi-cleavage fracture character.