The microstructure of localized deformation layers is inevitably altered in the machining process. In this study, the microstructural evolution of localized deformation layers due to tool wear in the turning of titanium alloy (Ti–6Al–4V) was examined via analysis of the grain boundaries, crystallographic texture, and phase transformation. The machined surface exhibited strong plastic activities within the flowing region in the case of a worn tool, and additional mechanical loads caused deeper deformation because of more ranges of the softened materials. The plastic activities in the localized deformation layer were enhanced by the additional thermomechanical loads because of tool wear, causing grain distortions, elongation, and deformed grain boundaries. High-density grain boundaries were clustered in the localized deformation layer with the increase in the tool wear, and the tool wear promoted the generation of local misorientation and a corresponding gradient. With the increase in the tool wear, the percentages of small grains increased, and various degrees of refinement occurred. The texture enhancement regions indicated that the preferential deformation texture was modified by the retained shearing, where the basal texture {10–10}〈0001〉 changed to shear C fibre textures. The phase transformation was analysed from the viewpoints of the variation in the relative peak intensities and the phase volume fractions. The microstructural evolution underwent a gradual transition process, which was determined by the thermomechanical conditions associated with the tool wear. The results have great significance for optimizing the tool wear values to improve the surface integrity and provide a novel avenue for material design.

中文翻译：

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机加工 Ti-6Al-4V 局部变形层中刀具磨损引起的微观结构演变

局部变形层的微观结构在加工过程中不可避免地发生改变。在这项研究中，通过分析晶界、晶体织构和相变，研究了钛合金 (Ti-6Al-4V) 车削过程中刀具磨损引起的局部变形层的微观结构演变。在刀具磨损的情况下，加工表面在流动区域内表现出强烈的塑性活动，并且由于软化材料的范围更大，额外的机械载荷会导致更深的变形。由于工具磨损，局部变形层中的塑性活动被额外的热机械载荷增强，导致晶粒扭曲、伸长和变形晶界。随着刀具磨损的增加，高密度晶界聚集在局部变形层中，刀具磨损促进了局部取向差和相应梯度的产生。随着刀具磨损的增加，小晶粒的百分比增加，并出现不同程度的细化。纹理增强区域表明，保留剪切改变了优先变形纹理，其中基底纹理{10-10}〈0001> 变为剪切 C 纤维纹理。从相对峰强度和相体积分数的变化角度分析相变。微观结构演变经历了一个逐渐转变的过程，这是由与工具磨损相关的热机械条件决定的。