热处理对铸造Ti15-3合金显微组织和力学性能的影响

Effect of heat treatment on microstructure and mechanical properties of cast Ti15-3 alloy

借助光学显微分析、TEM和SEM分析手段研究了不同热处理工艺对Ti15 - 3合金显微组织和力学性能的影响 .结果表明 :合金在铸态时的组织特征为粗大的 β相 ,由于合金中没有析出相的弥散强化作用 ,因而合金的强度低 .在不同温度时效处理后 ,在晶内和晶界析出α相 ,随着时效温度和时效时间的增加 ,析出相不断粗化 .与铸态相比 ,合金时效后强度大幅度提高而延伸率大幅度下降 ,在变形过程中 ,合金中的位错在析出相周围形成缠结 .合金塑性下降的原因主要是原始 β晶粒粗大和晶界析出相使晶界弱化 .

The effect of heat treatment on the microstructure and mechanical properties of cast Ti15-3 alloy have been studied by means of TEM, SEM and optical microscope, and results show microstructure of as cast alloy is characterized as large beta grains. For lack of strengthening action of precipitation, the tensile strength of the alloy is low but its elongation is high. After solution treatment flollowed by different aging treatments, it was observed that alpha phases precipitated in the grains or at the grain boundaries. With the aging temperature rising or holding time prolonged, the precipitation phases become coarser continuously. Compared with the as cast condition, the tensile strength of as heat treated alloy was considerably increased, but the elongation was dramatically decreased. Meanwhile, the dislocation tangled around the precipitation phases during the deformation process. The reasons for lower plasticity of alloy can be interpreted as the original large beta grains and the precipitation of alpha phases at the grain boundaries.