(1. 中南大學 材料科學與工程學院，長沙 410083；
2. Department of Chemical and Materials Engineering, University of Auckland, Auckland 1102, New Zealand)
摘 要: 利用兩種等通道角擠壓(ECAP)方法(普通單步ECAP和兩步ECAP)制備細晶ZK60合金。采用金相顯微鏡、掃描電鏡、透射電鏡和X射線衍射儀對合金的組織和織構(gòu)進行觀察，通過拉伸試驗研究不同ECAP方法對合金力學性能的影響。結(jié)果表明：與單步ECAP變形相比，兩步ECAP變形，由于降低了變形溫度，晶粒細化效果更好；經(jīng)過(240 ℃，4道次)+(180 ℃，4道次)兩步ECAP變形后，合金晶粒細化至約0.8 μm；合金的力學性能與材料的織構(gòu)密切相關(guān)，由于存在織構(gòu)軟化效應(yīng)，與擠壓態(tài)相比，經(jīng)單步ECAP變形后合金的強度有所降低，而伸長率明顯提高；但經(jīng)兩步ECAP變形后，由于細晶強化和亞結(jié)構(gòu)強化的作用，合金的強度得到提高。
關(guān)鍵字: ZK60 鎂合金；等通道角擠壓； 顯微組織；力學性能；動態(tài)回復；再結(jié)晶；織構(gòu)
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
(2. Department of Chemical and Materials Engineering, University of Auckland, Auckland 1102, New Zealand）
Abstract:Ultra-fine grain ZK60 magnesium alloys were fabricated separately by conventional single-step equal channel angular pressing (ECAP) processing and two-step ECAP processing. The microstructures and mechanical properties of the ZK60 magnesium alloys were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy and tensile test, and the texture was measured by XRD. The results show that, two-step ECAP is more effective in grain refinement than single-step ECAP process due to the lower deformation temperature. The grain size is refined to 0.8 μm after being processed with treatment of (240 ℃, 4 passes)+(180 ℃, 4 passes). Compared with the as-received ZK60 alloy, the single-step ECAP processed alloy has lower strength but higher elongation to failure. The decrease in strength is mainly ascribed to texture softening. However, after two-step ECAP process, the strength is improved due to the enhancement of fine grain strengthening and substructure strengthening.
Key words: ZK60 magnesium alloy; equal channel angular pressing; microstructure; mechanical properties; dynamic recovery; recrystallization; texture
