Enhancement of uniform plastic deformation for pure titanium foils by applying pre-strain combining with resistance heating method for microforming
Enhancement of uniform plastic deformation for pure titanium foils by applying pre-strain combining with resistance heating method for microforming
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DOI：
10.1016/j.jmrt.2020.08.108
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发表时间：
2020-11
期刊：
影响因子：
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通讯作者：
Q. Zheng;T. Furushima
中科院分区：
文献类型：
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作者：
Q. Zheng;T. Furushima
纯钛在室温下可成形性差，通常在高温下变形，变形后强度降低。提出采用预应变与电阻加热相结合的方法来提高其塑性，这种方法可以一次进行。利用RH拉伸试验机研究了该工艺对50μm厚纯钛箔拉伸变形的影响。用激光散斑数字图像相关(DIC)系统测量了全应变场。在10−2和10−1s−1的较高名义应变率下，在16 0℃的低温下施加1%~2%的单轴拉伸预应变，然后在名义应变率为10−3s−1的RT下进行拉伸试验。结果表明，虽然极限拉伸强度(UTS)随着预应变的增加略有下降，但最大降幅在4%以内，表明预应变对UTS的影响可以忽略不计。从DIC分析得到的应变分布在UTS处相对均匀。均匀延伸率随着预应变的增加而增加。最高增幅达到36%。结果表明，用RH加热厚度为50μm的钛箔的升温速度约为加热厚度为1 mm的钛片的340倍。RH的快速响应使所提出的工艺应用于制造微型零件的大规模生产成为可能。
Pure titanium (Ti) is usually deformed at elevated temperatures due to its poor formability at room temperature (RT), resulting in its strength reduction after deformation. Applying pre-strain combining with resistance heating (RH) method, which can be conducted at one procedure, was proposed to enhance its plasticity in this work. The influence of the proposed process on tensile deformation of pure Ti foils with 50 μm thick was investigated using a RH assisted tensile testing system. Full strain field was measured by a digital image correlation (DIC) system with laser speckles. Uniaxial tensile pre-strain ranging from 1% to 2% was applied at a low temperature of 160 °C with relatively high nominal strain rates of 10−2and 10−1s−1. Then tensile tests were conducted at RT with a nominal strain rate of 10−3s−1. As results, although the ultimate tensile strength (UTS) slightly decreased with increasing pre-strain, the maximum decreasing rate was within 4%, indicating that the effect of pre-strain on UTS is negligible. The strain distribution analyzed from DIC was relatively uniform at UTS. Uniform elongation increased with increasing pre-strain. The maximum increasing rate achieved 36%. It is confirmed that the heating rate using RH for heating Ti foils with 50 μm thick is about 340 times larger than that for heating Ti sheets with 1 mm thick. The quick response of RH makes it possible for the application of the proposed process to mass production for manufacturing microparts.