热连轧Ti-6Al-4V合金的蠕变行为及影响因素

Creep behaviors and effect factors of hot continuous rolled Ti-6Al-4V alloy

采用热处理、蠕变性能测试及位错组态的衍衬分析,研究热连轧Ti-6Al-4V合金的蠕变行为及影响因素。结果表明:经低于β相变点的固溶处理,合金的组织结构由高固溶度的等轴α相和网篮组织组成;随着固溶温度提高,网篮组织数量增多;经1000℃固溶处理后合金可获得完全网篮组织;与940℃固溶时效合金相比,经1000℃固溶时效合金在420℃、575MPa条件下具有较低的应变速率和较长的蠕变寿命;在试验的温度和应力范围内,计算出该合金的蠕变激活能为249.8kJ/mol;在蠕变期间,热连轧合金的变形机制是位错在具HCP结构的α相中发生双取向滑移,940℃固溶处理合金的蠕变机制是波浪状<a+c>位错在α相中发生锥面滑移,而经1000℃固溶处理合金的变形机制是(1/2)<111>位错在具BCC结构的β相中发生多系滑移;经1000℃固溶处理合金中所含的高含量富V的β相可提高合金蠕变抗力,这是合金具有较低应变速率和较长蠕变寿命的主要原因。

By heat treatment, measurement of creep properties and contract analysis of dislocations configuration, the creep behaviors and the effect factors of hot continuous rolled （HCR） Ti-6Al-4V alloy were investigated. The results show that, after the alloy solution treated at temperatures lower than ,8 phase transformation point, the microstructures of the alloy consist of the supersaturation equiaxial a phase and network basket structure. The quantities of the network basket structure increase as the solution temperature increases, and the full network basket structure may be obtained after solution-treated at 1 000℃. Compared with the alloy solution treated at 940 ℃, the alloy solution treated at 1 000℃ displays a lower strain rate and a longer creep lifetime under the conditions of the applied stress of 575 MPa at 420℃. In the range of the applied temperatures and stresses, the creep activation energy of the alloy is calculated to be 249.8 kJ/mol. The deformed mechanism of HCR alloy during creep is double orientation slipping of dislocations activated within a phase with HCP structure, while the deformed feature of the alloy solution treated at 940℃ is the wave-like （a＋c） dislocations activated on the pyramidal planes in a phase. After solution treated at 1 000℃, the deformed mechanism of the alloy is the multiple slipping of （1/2） （111） dislocations activated within,8 phase with BCC structure. In this alloy, the high volume fraction V-riched β phase may enhance the creep resistance of the alloy. This is the main reason why this alloy possesses relatively low strain rate and long creep lifetime.