摘要
目的Ti-6Al-4V双相钛合金因综合性能优异而广受关注,但其变形和加工困难,电火花线切割可以突破局限进行精细加工制备。旨在探究电火花线切割工艺参数对Ti-6Al-4V合金切割表面质量及效率的影响规律,并揭示对应参数下样品加工的表面硬度规律。方法考虑脉冲宽度、脉冲间隙、功放管数和运丝速度4个切割参数,以钛合金的切口平整度、重铸层厚度和切割时间为评价指标,设计正交实验,优化正交实验获得的最佳参数组合,使用纳米压痕仪对优化参数的样品进行表面硬度测试,得到加工表面硬度的分布规律。结果正交实验和极差分析结果显示,相较于脉冲间隙和运丝速度,脉冲宽度和功放管数对各指标的影响更大,而加工表面质量和加工效率呈对立关系。依据正交实验结果优化参数得到了3组可兼顾表面质量和加工效率的优化组合方案,分别有切口平整、切割时间短和重铸层厚度小等优点。纳米压痕测试结果显示,重铸层的硬度均高于热影响区与基体,为基体的1.2~3.9倍,而热影响区的硬度随功放管数的增大呈先升高再降低的趋势,其面积随功放管数增大而增大。结论对于电火花切割Ti-6Al-4V合金,脉冲宽度和功率放大管数为主要影响因素,可以通过正交实验获得最优工艺参数组合,并根据不同需要选择最适合的组合。电火花切割后样品表面重铸层的硬度最高,在表面处理时需去除,热影响区硬度存在明显起伏也需要去除。
Dual-phase titanium alloys,such as Ti-6Al-4V,are widely used in aerospace,biomedical,and marine applications owing to the desirable combination of their mechanical properties and relatively low density.However,the low thermal conductivity and high chemical reactivity of titanium alloys severely restrict the performance of conventional machining processes,particularly in achieving fine surface finishes and dimensional accuracy for geometrically complex components.Wire electrical discharge machining(WEDM),which leverages controlled electrical discharge erosion,overcomes the precision limitations of traditional methods through non-contact material removal.However,improper selection of electrical parameters will not only increase the thickness of the recast layer and heat-affected zone with mechanical property mismatches relative to the bulk material,but also deteriorate kerf flatness and reduce machining efficiency.The work aims to investigate the effect of WEDM parameters on the surface quality and machining efficiency of Ti-6Al-4V alloy,and elucidate the mechanical properties of machined surfaces under optimized conditions.To achieve systematic evaluation,an orthogonal experimental design was implemented with four controlled factors of pulse width,discharge gap,power amplifier tube number,and wire speed.Three performance metrics including kerf flatness,recast layer thickness,and machining time were selected as evaluation criteria.Range analysis was conducted to determine the hierarchical significance of parameter effects.Optimized parameter combinations were identified based on orthogonal experimental results.Nanoindentation tests were performed on samples processed with optimized parameters to evaluate the hardness gradients across the recast layer,heat-affected zone,and bulk material,with testing positions strictly confined to identicalα/βlamellar colonies to eliminate crystallographic anisotropy effects.The results demonstrated that pulse width and tube number had a more significant effect on the machining indices of Ti-6Al-4V alloy than discharge gap and wire speed.Although a trade-off relationship between surface quality and machining efficiency was identified,parameter optimization enabled three combinations achieving satisfactory coordination.Group 8 exhibited the best kerf flatness,Group 10 reached the shortest machining time,and Group 11 yielded the smallest recast layer thickness.Nanoindentation results revealed that the hardness of the recast layer was consistently higher than both the heat-affected zone and bulk material,measuring approximately 1.2 to 3.9 times that of the bulk material.Compared to the bulk material,the hardness of the heat-affected zone initially increased and then decreased with the increasing power amplifier tube numbers,while its areal extent expanded proportionally with tube numbers.Additionally,within the same colony,the recast layer and heat-affected zone exhibited greater hardness dispersion,whereas the bulk material remained relatively stable.This study indicates that the recast layer thickness is dominated by the pulse width,and the machining efficiency is determined by the tube number mostly in WEDM of Ti-6Al-4V alloy.Several optimal WEDM parameter combinations can be obtained through orthogonal experiments,allowing prioritization of precision or productivity based on application requirements.The recast layer,which exhibits brittleness and microstructural incompatibility with the bulk material,requires removal during post-processing.Although the heat-affected zone retains a microstructure similar to the bulk material,the significant hardness fluctuations necessitate concurrent removal.These findings provide practical guidance for selecting WEDM parameters to achieve precision and productivity in titanium alloy machining,particularly for safety-critical components demanding stringent surface integrity standards.
作者
徐鹏华
李沅沅
苗斌
孙梓洋
杨佳硕
郑士建
XU Penghua;LI Yuanyuan;MIAO Bin;SUN Ziyang;YANG Jiashuo;ZHENG Shijian(Tianjin Key Laboratory of Materials Laminating Fabrication and Interface Control Technology,School of Materials Science and Engineering,Hebei University of Technology,Tianjin 300401,China)
出处
《表面技术》
北大核心
2025年第12期134-144,共11页
Surface Technology
基金
国家自然科学基金(52101013)
河北省自然科学基金(E2022202004)。
关键词
钛合金
电火花线切割
正交实验
重铸层
硬度
titanium alloy
WEDM
orthogonal experiment
recast layer
hardness
