摘要
采用铜模喷铸制备了AZ91+0.75Ce快冷合金,研究了热处理温度及保温时间对合金非平衡组织热稳定性的影响。结果表明:铜模喷铸显著降低了镁合金的晶粒尺寸及二次枝晶间距,抑制了晶界β相形成并有效改善了Al-Ce稀土相形貌。经320℃时效处理后,快冷合金的晶界处优先形成不连续析出β相,其体积分数随时效时间的延长而增加,同时晶粒内部形成细小弥散的Al-Ce相。当时效温度升高到370℃时,快冷合金中初生α-Mg相形貌由枝晶转变为细小多边形,β相体积分数显著下降。由于Al-Ce析出相对高温晶粒生长的钉扎效应,快冷合金细晶组织的热稳定性得到提高。由于细晶强化和固溶强化的综合影响,快冷合金显微硬度为103 HV0.2,相比铸态合金提高了43%。经320℃时效处理8 h后,晶界的不连续析出β相及晶内连续析出的Al-Ce相导致合金硬度增加到129 HV0.2,相比原始快冷合金提高了25.2%。
Rapid solidified AZ91+0.75 Ce alloy was prepared by copper mould spray casting,and the effects of aging temperature and holding time on thermal stability of non-equilibrium microstructure of the alloy were studied.The results show that the size of the magnesium alloy and the spacing of secondary dendrites are significantly reduced by the copper mold spray casting,accompanied by the inhibition ofβphase at grain boundary and morphology improvement of Al-Ce phase.After aging at 320℃,discontinuousβphase precipitates preferentially at grain boundary and its volume fraction increases with the increase of aging time,and the fine dispersed Al-Ce phase is formed in the grain.When the aging temperature increases to 370℃,the morphology of primaryα-Mg phase of the rapid solidified alloy changes from dendrite to fine polygon,and the volume fraction ofβphase decreases significantly.Due to the pinning effect of Al-Ce precipitates against grain growth,the thermal stability of fine grain structure of the rapid solidified alloy is improved.Due to the comprehensive influence of fine grain strengthening and solid solution strengthening,the microhardness of the rapid solidified alloy is 103 HV0.2,which is 43%higher than that of the as cast alloy.After aging at 320℃for 8 h,the microhardness of the alloy increases to 129 HV0.2 due to the discontinuous precipitation ofβphase at grain boundary and continuous precipitation of Al-Ce phase within the grain,which is 25.2%higher than that of the original rapid solidified alloy.
作者
朱堂葵
杨伟
刘灵
ZHU Tang-kui;YANG Wei;LIU Ling(School of Electromechanical and Information Technology,Yiwu Industrial and Commercial College,Yiwu 322000,China;School of Aeronautical Manufacturing Engineering,Nanchang Hangkong University,Nanchang 330063,China)
出处
《材料热处理学报》
CAS
CSCD
北大核心
2021年第12期36-43,共8页
Transactions of Materials and Heat Treatment
基金
国家自然科学基金(51461032,52061032)
义乌工商职业技术学院重点科研项目(ZD2021CS414-02)
江西省教育厅资助项目(GJJ180513)。
关键词
稀土镁合金
冷却速率
非平衡凝固
热稳定性
rare earth magnesium alloy
cooling rate
non-equilibrium solidification
thermal stability
