Effect of the subsolvus and supersolvus solution treatments on the basket-weave microstructure, room and high temperature properties of TC21 alloy

Abstract

In this study, two different microstructures were obtained after subsolvus solution treatment (910 °C + 550 °C) and supersolvus solution treatment (1010 °C + 550 °C) in TC21 alloy. The relationship of microstructure with room and high temperature properties was studied. The results showed that at room temperature, both samples after two treatments had high hardness. At room temperature, the subsolvus sample had high tensile strength of 1070 MPa and moderate plasticity and impact toughness, while the supersolvus sample was hard and brittle. The high strength and toughness of subsolvus sample was owing to its clear basket-weave structure within finer β grains which contributes to fine grain strengthening and the increase of crack tortuosity. Poor plasticity and toughness of supersolvus sample could be mainly attributed to its incomplete basket-weave structure, coarse β grains, Widmannstatten α and some coarse α-phase in the grain boundary. Both samples showed excellent high temperature tensile properties and stability at 400 °C, the tensile strength was still as high as 1000 MPa while plasticity was significantly improved. With the tensile temperature increasing to 600 °C, the alloys showed obvious softening as the tensile strength significantly decreased and elongation increased.