ABSTRACT

Shape memory alloy (SMA), also called memory metal, is a smart material that exhibits unique shape memory effect and superelasticity properties. NiTi alloys attract researchers because of their myriad applications in areas such as aerospace, medicine, and robotics. In the present NiTi SMA fabrication, the Cu and Zr elements were added to increase the martensitic transformation temperatures. The current study focuses on the machining of high-temperature Ni₄₄Ti₅₀Cu₄Zr₂ SMA by coated wire electric discharge machining (W-EDM). Machining quality features like surface undulation and material removal were studied by considering current (I), servo voltage (SV), pulse on time (T_on), angle of cut (A_C), and pulse off time (T_off). Parametric analysis of machining characteristics has been investigated by conducting experiments following the response surface approach based central composite design (RSM-CCD). It was found that MRR has increased by 57% and Ra by 58% with a gradual increase in pulse on time and applied current and decreases gradually on increasing servo voltage and pulse off time. XRD analysis reveals the presence of an oxide layer on the wire-EDMed surface. The study of SEM confirms the formation of the melted layer, micro-voids, and micro-cracks, resulting in surface irregularities.

摘要

形状记忆合金 (SMA)，也称为记忆金属，是一种具有独特形状记忆效应和超弹性特性的智能材料。NiTi 合金因其在航空航天、医学和机器人等领域的无数应用而吸引了研究人员。在目前的 NiTi SMA 制造中，添加了 Cu 和 Zr 元素以提高马氏体转变温度。目前的研究重点是通过涂层线材电火花加工 (W-EDM) 加工高温 Ni ₄₄ Ti ₅₀ Cu ₄ Zr ₂ SMA。通过考虑电流 (I)、伺服电压 (SV)、脉冲导通时间 (T _on )、切削角 (A _C) 和脉冲关闭时间 (T _off )。通过遵循基于响应面方法的中心复合设计 (RSM-CCD) 进行实验，对加工特性的参数分析进行了研究。发现随着脉冲导通时间和施加电流的逐渐增加，MRR 增加了 57%，Ra 增加了 58%，并随着伺服电压和脉冲关闭时间的增加而逐渐减小。XRD 分析揭示了在线EDMed 表面上存在氧化层。SEM 研究证实了熔化层、微孔洞和微裂纹的形成，导致表面不规则。