半固态等温热处理对铸态AZ80镁合金组织影响.pdf

学兔兔 半固态等温热处理 对铸态AZ80镁合金组织的影响 Effects of Semi—Solid IsothermaI Heat Treatment on Structure of Magnesium Alloy AZ80 艾秀兰 杨 军 权高峰 (大连交通大学辽宁省轨道交通关键材料重点实验室，辽宁省大连市 1 16028) 摘要：研究了等温热处理温度和保温时间对铸态AZ80镁合金半固态组织演变的影响。研究结果表明：在 热处理过程中，随保温时间的延长，初生 相演变过程是，首先由大部分粗大的树枝晶二次枝晶臂合并成为大 块状，而后大块状晶粒在晶粒内部及晶界处液相和固液界面的曲率共同作用下熔化分离为小块状，继续保温 则圆整化；保温时间相同，等温处理的温度越高，枝晶演变过程越快，保温温度越高或保温时间越长，球状晶粒 也容易趋于长大。AZ80镁合金半固态成形所需的最佳工艺条件为加热温度570~C左右，保温时间30min。 关键词：镁合金，半固态成形，等温热处理，组织演变 中图分类号：TG146．2+2；文献标识码：A；文章编号：1006—9658(2009)01—3 Abstract：The effects of isothermal heat treatment temperature and holding time on microstrueture evolution of AZ80 magnesium alloy in semi—solid state have been studied．The results showed that during heat treatment，with holding time extension，aphase evolution process is as follows：the most secondary arms of coarse dendrite grains were combined to form big block crystal grains first；Then under the action of curvature of liquidus in grain and grain‘。 boundary，as well as curvature in interface between solidus and liquidus，the block crystal grains was melted and separated to small block grains and turn to spheroidal shape when the holding time was identica1．The higher the isothermal heat treatment temperature was，the faster the process of mierostructure evolution was．The higher the holding temperature or the longer the holding time was，the more susceptible for the spheroidal structure to grow up． The optimal semi-solid structure for semi-solid-forming can be obtained with holding time for 30rain at about 570~C． Keywords：Mg alloy，semi—solid forming，isothermal heat treatment，mierostrueture evolution 镁合金是目前工业应用中最轻的金属结构材 粗大的／3一Mg。 A1， 容易破裂，形成裂纹源，引起低塑 料，具有高的比强度和