The current study presents the fatigue crack growth behaviour of titanium alloy Ti6Al4V parts manufactured by selective laser melting (SLM), obtained as standard 6 mm thick compact specimens (CT). Both the crack propagation under constant amplitude loading and the transient crack growth behaviour after the application of overloads were studied. The effect of the mean stress and the transient retardation behaviour were analysed using the crack closure parameter, obtained both by compliance and digital image correlation techniques. A reduced crack closure level for the stress ratio $$\hbox {R}=0$$ R = 0 was detected and for $$\hbox {R}=0.4$$ R = 0.4 no crack closure was observed. The digital image correlation technique showed better results in the Paris regime and during the transient retardation behaviour. The overload application produced crack growth retardation due to the increase of the crack closure effect. The failure surfaces showed a transgranular crack growth in $$\upbeta $$ β phase contouring the martensitic $$\upalpha $$ α phase.

中文翻译：

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激光选区熔化制备 Ti6Al4V 合金试样的疲劳裂纹扩展行为

目前的研究展示了通过选择性激光熔化 (SLM) 制造的钛合金 Ti6Al4V 零件的疲劳裂纹扩展行为，获得了标准 6 毫米厚的紧凑试样 (CT)。研究了恒幅载荷下的裂纹扩展和施加过载后的瞬态裂纹扩展行为。使用裂纹闭合参数分析平均应力和瞬态延迟行为的影响，该参数通过柔量和数字图像相关技术获得。检测到应力比 $$\hbox {R}=0$$ R = 0 的裂纹闭合水平降低，并且 $$\hbox {R}=0.4$$ R = 0.4 没有观察到裂纹闭合。数字图像相关技术在巴黎制度和瞬态延迟行为期间显示出更好的结果。由于裂纹闭合效应的增加，过载应用产生了裂纹扩展延迟。失效表面显示出在 $$\upbeta $$ β 相中的穿晶裂纹扩展，轮廓为马氏体 $$\upalpha $$ α 相。