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研究了准β热处理工艺窗口参数(保温时间和加热温度)对损伤容限型TC4-DT钛合金的疲劳裂纹扩展行为的影响,并采用金相显微镜和扫描电镜从显微组织、裂纹扩展路径及断口形貌进行了分析对比。结果表明:随着保温时间从5min延长至15min,原始β晶粒尺寸从130?m增大到230?m,转变点处ΔKt由17.5MPa?m1/2增大至19.4MPa?m1/2,当10MPa?m1/2≤ΔK≤20MPa?m1/2的低应力范围,裂纹扩展速率降低;随着加热温度从988℃升高至998℃,原始β晶粒尺寸从130?m增大至240?m,转变点处ΔKt由17.5MPa?m1/2增大至18.0MPa?m1/2,转折点前的裂纹扩展区的裂纹扩展速率降低;当温度继续升高至1008℃时,原始β晶粒尺寸增大至400?m,转折点处ΔKt增大至20.5MPa?m1/2,裂纹扩展速率在转折点附近降低,但在ΔK≥20.5MPa?m1/2的较大应力区域时,裂纹扩展速率无明显变化;温度升高或保温时间延长,裂纹扩展路径曲折度增加,二次裂纹数量增多、深度增加,断口表面粗糙度降低。
The influence of window parameters of quasi-β heat treatment process (holding time and heating temperature) on the fatigue crack growth behavior of the damage tolerance type TC4-DT titanium alloy was studied. The microstructure, crack propagation path, Fracture morphology analysis and comparison. The results showed that with increasing holding time from 5 min to 15 min, the original β grain size increased from 130 μm to 230 μm, and ΔKt increased from 17.5 MPa? M1 / 2 to 19.4 MPa? M1 / 2 at the transformation point. When the stress range of 10MPa? M1 / 2≤ΔK≤20MPa? M1 / 2 is low, the crack propagation rate decreases. As the heating temperature increases from 988 ℃ to 998 ℃, the original β grain size increases from 130μm to 240 m, the ΔKt at the transition point increased from 17.5 MPa? m1 / 2 to 18.0 MPa? m1 / 2, and the crack growth rate in the crack propagation zone before the turning point decreased. When the temperature continued to increase to 1008 ° C, The size increases to 400 μm, ΔKt increases to 20.5 MPa? M1 / 2 at the turning point, and the crack propagation rate decreases near the turning point. However, in the larger stress region of ΔK≥20.5 MPa? M1 / 2, the crack growth rate is Obviously. The temperature increase or holding time prolongs, the tortuosity of the crack propagation path increases, the number of secondary cracks increases, the depth increases, and the fracture surface roughness decreases.