Effect of grinding parameters on microstructure evolution of TC21 titanium alloy with bimodal starting microstructure

This study aims to investigate the deformation behavior of two-phase titanium alloy Ti–6Al–3Mo–2Zr–2Sn–2Nb–1Cr (TC21) during grind hardening (GH) process. According to dynamic material modeling (DMM) combine Kumar’s instability criterion, the processing maps were constructed to discuss processing properties of material. Results suggest that the ideal processing region is in the temperature of 880 °C, strain rate range 10−3-0.03s−1. The evolution mechanism of α phase was revealed using TEM microstructural analysis under different grinding conditions. It is interesting that, some secondary-precipitated α phase with approximate orientation usually combine to form lamellar α colonies, while some ones with different orientations split to short rod-like or globular structure particularly at higher grinding depth. The optimum grinding parameters for TC21 is at grinding depth range 60–90 μm, wheel speed of 20  m s−1 followed by aging treatment. Most of all, the GH technology has a significantly advantage than heat treatment for exhibiting higher micro-hardness and lower friction coefficient.