Abstract:The microstructure and phase composition of semi-solid Ti14 alloy (α-Ti+Ti2Cu) with different cooling modes (furnace cooling—FC, air cooling—AC and water quenching—WQ) were investigated by OM, SEM and XRD. The results show that the three cooling modes have no effects on the phase composition of Ti14, but influence the morphology and distribution of Ti2Cu. The microstructure of Ti14 after furnace cooling consisted of granular Ti2Cu precipitates, which distributed in a certain direction presenting strip and dentritic structure. After air cooling, Ti2Cu precipitates were granular or lamellar in the grains and grain boundaries; while after water quenching, the microstructure was composed of coarse grain boundary, and no evident precipitates were observed. The semi-solid Ti14 alloy undergoes peritectic solidification during cooling process. The peritectic reaction occurs in the liquid/β/Ti2Cu trijunctions region, which makes the solute distribution there irregular, and the trijunctions dynamics quite complicated. Meanwhile the cooling modes also influence the peritectic reaction extent, and thus affect the following eutectoid, resulting in different microstructure with different cooling modes.