Microstructural evolution of an ECAE-formed ZK60-RE magnesium alloy in the semi-solid state
Microstructural evolution of an ECAE-formed ZK60-RE magnesium alloy in the semi-solid state
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DOI：
10.1016/j.msea.2008.12.042
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发表时间：
2009-04
期刊：
影响因子：
6.4
通讯作者：
Zude Zhao;Qiang Chen;Yanbin Wang;D. Shu
中科院分区：
文献类型：
--
作者：
Zude Zhao;Qiang Chen;Yanbin Wang;D. Shu
先前的文献已经提出或报道了通过应变诱导熔融激活（SIMA）工艺制备AZ91D镁合金半固态坯料。然而，尚未对 Mg-Zn-Zr 系列镁合金进行详细研究。本文研究了添加稀土（RE）的ZK60镁合金在部分重熔过程中的显微组织演变。 SIMA 工艺中引入等通道角挤压 (ECAE)，以取代传统的镦粗或挤压。结果表明，ECAE成功挤压铸态ZK60-RE镁合金。 ECAE 形成的 ZK60-RE 的半固态微观结构由晶界液膜包围的细小球状晶粒组成。当固体分数从 0.75 (600°C) 降低到 0.65 (615°C) 时，立方粗化速率常数 K 从 255 增加到 371μm3s−1。随着 ECAE 次数的增加，这意味着畸变能增加，晶粒尺寸更细，液体形成率提高。这种研究鼓励人们相信，ECAE与半固态部分重熔相结合，可以生产出晶粒细小、球状的镁合金半固态坯料，适合半固态加工。
AZ91D magnesium alloy semi-solid billets prepared by the strain-induced melt activation (SIMA) process have been proposed or reported in previous literature. However, no detailed investigation has been conducted regarding Mg–Zn–Zr series magnesium alloys. In this paper, the microstructural evolution of ZK60 magnesium alloy with a rare earth (RE) addition during partial remelting has been studied. Equal channel angular extrusion (ECAE) was introduced into the SIMA process to replace conventional upset or extrusion. The results show that as-cast ZK60-RE magnesium alloys are successfully extruded by ECAE. The semi-solid microstructure of ECAE-formed ZK60-RE consists of fine and spheroidal grains surrounded by grain boundary liquid films. The cubic coarsening rate constant, K, increases from 255 to 371μm3s−1when the solid fraction decreases from 0.75 (600°C) to 0.65 (615°C). With increasing numbers of ECAE passes, which means increasing distortion energy, grain sizes are finer and liquid formation rates are enhanced. This kind of research encourages the belief that the combination of ECAE and partial remelting in the semi-solid state can produce magnesium alloy semi-solid billet with fine and spheroidal grains, which is suitable for semi-solid processing.