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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。
The effect of aging time on the microstructure and mechanical properties of low cost β (LCB) Ti-6.6Mo-4.5Fe-1.5Al titanium alloy was studied. The relationship between microstructure and fatigue fracture cracking was also studied. Prolonging the aging time contributes to the increase of the volume fraction of secondary α and β grains and the partial spheroidization of the initial α phase. The tensile strength (1565MPa) and the fatigue limit (750MPa) were the highest when the alloy was heat-treated at 500 ° C for 0.5h, while the alloy obtained after heat treatment at 500 ° C for 4h had the lowest tensile strength (1515MPa) and the lowest fatigue limit (625MPa). The fracture mode of alloy treated by heat treatment at 500 ° C for 4h was transgranular fracture, while the fracture mode of alloy treated by heat treatment at 500 ° C for 0.5h was the combination of transgranular fracture and intergranular fracture. Cracks formed on the outer surface of the fatigue specimen extend along the initial alpha phase on the beta grain boundaries.