半固态锻造Ti14合金的拉伸性能和组织演变特征

摘要

通过室温和高温拉伸性能测试,对比研究了Ti14合金经常规锻造(950℃)和半固态锻造(1 000℃和1 050℃)后试样在不同温度区间的宏观力学行为,分析了微观组织演变规律、断口微观形貌及断裂特征.结果表明:合金经半固态锻造后表现出高强度、低塑性的力学特征,随着半固态锻造温度的升高,合金力学性能下降.半固态锻造过程中组织的变化是引起力学性能差异的主要原因,而组织演变的主要特征是Ti2Cu析出相形态和分布的变化.随着半固态温度的升高,更多的液相在晶界析出,并在凝固过程中析出大量板条状Ti2Cu相,最终在晶界上形成偏析带组织.这种带状组织在拉伸过程中引发了解离断裂,导致了低塑性.此外,通过再结晶退火可以有效地细化半固态组织,改善强度性能.%Tensile properties of a new α+Ti2Cu alloy after solid forging at 950 ℃ and semi-solid forging at 1 000 ℃ and 1 050 ℃ were investigated over the temperature range of 20-600 ℃.The results reveal that high strength and low ductility are obtained in all semi-solid forged alloys.Tensile properties decrease as the semi-solid forging temperature increases,and cleavage fractures are observed after semi-solid forging at 1050 ℃.The variations in tensile properties are attributed to the coarse microstructures obtained in the semi-solid alloys.It is found that the elevated semi-solid temperatures lead to more liquid precipitates along the prior grain boundaries,which increases the peritectic precipitation and formation of Ti2Cu precipitation zones during re-solidification.Recrystallization heat treatment leads to fine microstructure of semi-solid forged alloys,resulting in improvement of tensile properties.