(1. 清華大學(xué) 機(jī)械工程系 先進(jìn)成形制造教育部重點(diǎn)實(shí)驗(yàn)室，北京 100084；
2. 南陽師范學(xué)院 材料科學(xué)與工程系，南陽 473004；
3. 中鋁鄭州研究院 綠色冶金研究所，鄭州 450001)
摘 要: 通過疲勞試驗(yàn)機(jī)/掃描電鏡的原位觀察、以及掃描電鏡/圖像分析軟件的定量分析，研究AZ31鎂合金鑄軋板材熱變形過程中的空洞演化行為。結(jié)果表明：鎂合金板材熱變形過程中，空洞首先在晶界尤其是在三叉交界處形核，隨后不斷長(zhǎng)大和聚合，導(dǎo)致材料斷裂；空洞的長(zhǎng)大具有方向選擇性，與拉伸軸方向垂直的空洞容易長(zhǎng)大。空洞長(zhǎng)大機(jī)制的理論模型計(jì)算與試驗(yàn)結(jié)果對(duì)照表明：孔徑小于2 μm小空洞的圓度系數(shù)接近1，其主要長(zhǎng)大機(jī)制為晶界擴(kuò)散；孔徑大于2 μm大空洞的圓度系數(shù)和取向角均比較分散，其主要長(zhǎng)大機(jī)制是塑性變形。
關(guān)鍵字: AZ31鎂合金；鑄軋板材；空洞；擴(kuò)散；塑性變形
hot deformation
（1. Key Laboratory for Advanced Manufacturing by Materials Processing Technology, Ministry of Education,
Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China;
2. Department of Materials Science and Engineering, Nanyang Normal University, Nanyang 473006, China;
3. Green Metallurgy Research Department, Zhengzhou Research Institute, CHAICO, Zhengzhou 450001, China）
Abstract: The cavity evolution behavior of twin-roll-cast AZ31 magnesium alloy sheet during hot deformation was investigated by in-situ SEM observation on the fatigue testing machine, and the characteristics of cavity were quantitative measured using graphical analysis software. The results show that the cavity nucleates while the twin-roll-cast AZ31 alloy sheet deforms, and the cavity starts on the tri-grain boundary. The continuously growth and coalescence of the cavities induce the material fracture. The cavities grow directionally and prefer to grow along axis perpendicular to the loading axis. The comparison between the theory analysis and experimental results shows that the shape of the cavity with diameter less than 2 μm is nearly spherical, and the main cavity growth mechanisms is diffusion. In contrast, the cavities with diameter larger than 2 μm tend to be elongated with the long axis parallel to the loading axis, the main cavity growth mechanisms is plasticity deformation.
Key words: AZ31 magnesium alloy; twin-roll-cast sheets; cavity; diffusion; plasticity deformation
