低成本β钛合金热处理后的显微组织变化和力学性能(英文)

研究了时效时间对低成本β(LCB)Ti-6.6Mo-4.5Fe-1.5Al钛合金的显微组织和力学性能的影响,以及显微组织与疲劳断裂裂纹的产生、延伸的联系。延长时效时间有助于二次α相和β晶粒体积分数的增多以及初始α相的部分球化。在500°C下热处理0.5h的合金得到的拉伸强度最大(1565MPa),疲劳极限最高(750MPa);而在500°C下热处理4h的合金得到的拉伸强度最小(1515MPa),疲劳极限最低(625MPa)。在500°C下热处理4h的合金的断裂模式为穿晶断裂,而在500°C下热处理0.5h的合金的断裂模式为穿晶断裂和沿晶断裂的混合。在疲劳样品的外表面形成的裂纹沿β晶界上初始α相延伸。

Microstructure evolution and mechanical properties of heat treated LCB titanium alloy

The influence of ageing time on microstructure and mechanical properties of low-cost beta （LCB） titanium alloy with a chemical composition of Ti-6.6Mo-4.5Fe-1.5Al was investigated. The correlation between microstructure and fatigue crack initiation and growth was also studied. Increasing ageing time tended to increase the volume fraction of the secondary α-precipitates, β-grain size and partial spheroidization of primary α-phase. The maximum tensile strength （1565 MPa） and fatigue limit （750 MPa） were obtained for the samples aged at 500 °C for 0.5 h, while the minimum ones of 1515 MPa and 625 MPa, respectively, were reported for the samples aged at 500 °C for 4 h. The samples aged at 500 °C for 4 h showed a transgranular fracture mode. However, the samples aged at 500 °C for 0.5 h revealed a mixture fracture mode of transgranular and intergranular. The formed cracks on the outer surface of the fatigue samples were found to propagate through the β-grains connecting the primary α-particles existing at the β-grain boundaries.