热处理工艺对Ti-3Al-6Mo-2Fe-2Zr合金组织和性能的影响

采用OM、SEM和XRD等方法研究了固溶时效热处理对近β型钛合金(Ti-3Al-6Mo-2Fe-Zr)显微组织、力学性能及耐腐蚀性能的影响。结果表明,随着固溶温度的升高,初生α相的含量逐渐降低,经930 ℃固溶处理后,合金为单一β相。固溶温度在830 ℃以下时,随着固溶温度的升高,初生α相逐渐转变为β相,第二相强化作用减弱,合金强度逐渐降低,塑性逐渐提高,断裂方式为微孔聚集型;固溶温度在830 ℃以上时,随着固溶温度的升高,β相晶粒逐渐粗化,合金强度降低,塑性下降,断裂方式由微孔聚集型断裂向解理断裂转变。随着固溶温度从780 ℃升高至930 ℃,初生α相的含量降低,β/α相界逐渐减少,耐腐蚀性能提升。经780 ℃固溶1 h(水冷),500 ℃ 时效6 h(随炉冷却)处理后,细小针状的次生α相于亚稳β相中沉淀析出,合金强度显著提高,但塑性下降。

Influence of heat treatment process on microstructure and properties of Ti-3Al-6Mo-2Fe-2Zr alloy

Influences of solution and aging treatment on microstructure, mechanical properties and corrosion resistance of near-β titanium alloy (Ti-3Al-6Mo-2Fe-Zr) were studied by means of optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD). The results show that with the increase of solution temperature, the content of primary α phase gradually decreases. After solid solution treatment at 930 ℃, the alloy phase composition becomes a single β phase. When the solution temperature is below 830 ℃, the primary α phase gradually transforms into β phase with the increase of solution temperature. The strengthening effect of the second phase is weakened, resulting in a decrease in strength and an increase in plasticity. When the solution temperature is above 830 ℃, the β-phase grains gradually coarsen with the increase of solution temperature, leading to a decrease in strength and plasticity. The fracture mode also changes from micropore coalescence fracture to cleavage fracture. The corrosion resistance is improved as a result of the decrease of content of α phase and β/α phase boundary, as the solution temperature increases from 780 ℃ to 930 ℃. After the solution treatment at 780 ℃ for 1 h followed by water quenching and aging treatment at 500 ℃ for 6 h followed by furnace cooling, the fine needle-like secondary α phase precipitates within the metastable β phase, resulting in an increase in strength and a decrease in plasticity.