(1. 東北大學(xué) 材料與冶金學(xué)院，沈陽(yáng) 110004；2. 北京航空制造工程研究所，北京 100024)
摘 要: 920 ℃、應(yīng)變速率為1×10−3和2×10−4 s−1時(shí)，對(duì)不同初始晶粒尺寸(2.6、6.5和16.2 μm)的Ti-6Al-4V合金進(jìn)行超塑性拉伸變形。采用光學(xué)顯微鏡、透射電鏡觀察變形后的顯微組織。結(jié)果表明，初始晶粒尺寸的不同對(duì)超塑性變形中的組織演變及變形機(jī)制有著顯著的影響。拉伸變形中晶粒明顯粗化，變形誘發(fā)晶粒長(zhǎng)大是超塑性變形組織的重要特征之一；隨著變形程度的增大，應(yīng)變誘發(fā)的晶粒長(zhǎng)大顯著增大，并且遠(yuǎn)大于靜態(tài)長(zhǎng)大的增幅。對(duì)于細(xì)晶粒材料(2.6和6.5 μm)，位錯(cuò)運(yùn)動(dòng)協(xié)調(diào)的界面滑動(dòng)是其變形的主要機(jī)制。而對(duì)于晶粒較粗的材料(16.2 μm)，超塑變形機(jī)制是晶界滑動(dòng)與晶內(nèi)位錯(cuò)運(yùn)動(dòng)的共同作用。隨著晶粒尺寸的增大，以晶界滑動(dòng)為主的變形方式逐漸轉(zhuǎn)向以晶內(nèi)位錯(cuò)運(yùn)動(dòng)為主。
關(guān)鍵字: Ti-6Al-4V合金；超塑性變形；晶粒尺寸；晶粒長(zhǎng)大；變形機(jī)制
（1. School of Materials and Metallurgy, Northeastern University,Shenyang 110004, China;2. Beijing Aeronautical Manufacturing Technology Research Institute,Beijing 100024, China）
Abstract:Superplastic tensile tests were carried out for Ti-6Al-4V alloy using different initial grain sizes (2.6, 6.5 and 16.2 μm) at 920 ℃ with an initial strain rate of 1×10−3 and 2×10−4 s−1. To get an insight into the effect of grain size on microstructural evolution and superplastic deformation mechanisms, the microstructures of deformed alloy were investigated by using an optical microscope and transmission electron microscope. The results indicate that there is dramatic difference in the superplastic deformation mode of fine and coarse grained Ti-6Al-4V alloys. Grain growth is clearly observed, and strain inducing grain growth is one of the important microstructural characteristics during superplastic deformation. Moreover, grain growth induced by strain becomes dramatic with the increase of deformation, which is obviously larger than the static growth. For fine grained material, boundary sliding accommodated by dislocation motion is the main deformation mechanisms. For coarse grained material, superplastic deformation is accommodated by the mixture of grain boundary sliding and intragranular dislocation motions. It indicates a transition from boundary sliding to matrix deformation with the coarsening of grains.
Key words: Ti-6Al-4V alloy; superplastic deformation; grain size; grain growth; deformation mechanism
