Cu 含量对Ti-Cu合金半固态可锻性及锻造后力学性能的影响

通过镦锻试验和模锻实验研究了Ti-Cu系合金半固态锻造行为，并对锻材进行了拉伸试验，讨论了Cu含量对半固态可锻性及力学性能的影响。结果表明：1000 °C至1150°C半固态锻造较常规锻造具有较小的顶锻压力；其中，1000 °C至1050°C间半固态锻造的Ti-Cu系合金均表现出较好的可锻性，在75%的锻造变形量下无明显缺陷。分析认为，Ti-Cu系列合金中含有较多的低熔点Ti2Cu相，随着半固态温度升高或Cu含量的增加，材料中的液相含量增加，增加的液相含量对变形起到润滑作用，减少了固相变形引起的应力集中，有效的降低了变形抗力，改善了成形性。力学性能研究表明：半固态锻造Ti-Cu系合金较常规锻造合金强度升高，塑性降低。随着Cu含量的升高，合金的强度明显提升，塑性降低。分析认为：力学性能的变化主要是由于Ti2Cu相析出含量、形态和分布相关，随着Cu含量和半固态温度的升高，更多Ti2Cu相在晶内和晶界析出，引起析出强化作用，同时，晶界析出的针状Ti2Cu相形成了偏析带，降低了合金塑形。

Effect of Cu concentration on the semi-solid formability and mechanical properties of Ti-Cu alloy

The formability during semi-solid deformation of Ti-Cu alloys and its mechanical properties after semi-solid forging are investigated. The formability is evaluated by upsetting and die forging tests. Tensile test is also performed to study the mechanical properties of Ti-Cu alloy after semi-solid forging. The results show that low upsetting force can be obtained in the semi-solid state ranging from 1000 °C to 1150°C, which is better than by conventional processing. Die forging tests show excellent workability with a forging ratio of 75% at the temperatures ranging from 1000 °C to 1050°C. The Ti2Cu phase increases with the increase of Cu concentration, and more liquid precipitates during semi-solid deformation at higher temperatures and Cu concentrations, which relaxes the stress concentration caused by solid deformation and improves the formability. Tensile test reveals that semi-solid forged Ti-Cu alloy exhibits higher strength and lower ductility than conventional forged alloy. The Ti-Cu alloy has lower ductility and higher strength with the increasing of Cu concentration. The difference in tensile properties is attributed to the varieties of Ti2Cu precipitates at different Cu concentration and semi-solid forging temperature.