Influence of High-Energy Pulse Current on the Mechanical Properties and Microstructures of Ti-6Al-4V Alloy
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Influence of High-Energy Pulse Current on the Mechanical Properties and Microstructures of Ti-6Al-4V Alloy Zhiyong Zhao, Guofeng Wang, Hongliang Hou, Baoshuai Han, Yanling Zhang, and Ning Zhang (Submitted May 7, 2017; in revised form August 30, 2017; published online September 25, 2017) This study reported the effect of the high-energy pulse current on the mechanical properties and microstructure evolution of Ti-6Al-4V alloy in the compression deformation process. The electroplastic compression (EC) of Ti-6Al-4V alloy was performed with discharge voltages of 50 and 70 V and strain rates of 0.01 and 0.03 s21, respectively. The results show that the mechanical properties of Ti-6Al-4V alloy greatly change under the influence of the high-energy pulse current. Metallographic examination and x-ray diffraction are performed to observe the microstructural evolution of the alloy. An obvious dynamic globularization occurs at the later stage of the EC process even though the temperature of the samples is relatively low. An a–b phase change also occurs during the EC process. The microstructural evolution of Ti6Al-4V alloy during the EC process is mainly attributed to the thermal and athermal effects of electropulsing, which promotes the dislocation motion and nucleation rate of dynamic globularization. Keywords
dynamic globularization, electroplastic compressing, phase change, Ti-6Al-4V alloy
1. Introduction Titanium and titanium alloys are the most popular materials in the fields of aerospace and aviation, navigation, and shipping. By having the most excellent comprehensive properties of a + b alloy, Ti-6Al-4V alloy has attracted the attention of designers due to its high specific strength and stiffness, good formability, reasonable ductility, and ability to withstand high temperatures and resist corrosion. This material has also been widely used in aeroengine, gas turbines, and other weightcritical applications (Ref 1-3). However, titanium alloys are difficult to be processed using conventional technology owing to its several inherent properties. Hot deformation in actual industrial processes, such as hot forging or rolling, is extensively used for manufacturing the semi-finished and finished products of Ti-6Al-4V alloy (Ref 4-6). The mechanical properties and forming process largely depend on the microstructure of materials. Different microstructure of the two-phase Ti-6Al-4V alloy, including Widmanstatten, basket-weave, equiaxed and duplex microstructures, can be obtained by heat treatment and plastic deformation (Ref 7). Ti6Al-4V alloy with equiaxed microstructure was considered to have good comprehensive mechanical properties. Thermomechanical treatment is an effective method to obtain equiaxed Zhiyong Zhao and Baoshuai Han, National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China and Beijing Aeronautical Manufacturing Technology Research Institute, Beijing 100024, China; Guofeng Wang, National Key Laboratory for Precision Ho
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