稀土钇、铈变质真空差压铸造ZL114A合金的力学性能及蠕变机制  

Mechanical Properties and Creep Mechanism of Yttrium and Cerium Modified ZL114A alloy via Vacuum Counter-pressure Casting

作　　者：陈义斯 芦刚 严青松 黄普英 徐翩 毛蒲 周泽远 CHEN Yisi;LU Gang;YAN Qingsong;HUANG Puying;XU Pian;MAO Pu;ZHOU Zeyuan(National Defense Key Disciplines Laboratory of Light Alloy Processing Science and Technology,Nanchang Hangkong University,Nanchang 330063)

机构地区：[1]南昌航空大学轻合金加工科学与技术国防重点学科实验室,南昌330063

出　　处：《机械工程学报》2023年第18期186-195,共10页Journal of Mechanical Engineering

基　　金：国家自然科学基金(51861027);江西省研究生创新专项资金(YC2021-S672);轻合金加工科学与技术国防重点学科实验室开放课题研究基金(EG201903451,EG202103418)资助项目。

摘　　要：为进一步提升复杂薄壁铝合金构件力学性能,尤其是抗高温蠕变能力,基于真空差压铸造工艺,分别采用稀土钇(Y)、铈(Ce)元素对ZL114A进行变质处理。系统测试了样品硬度、拉伸性能、蠕变应变,观察分析稀土元素对合金组织结构演变的影响,揭示变质ZL114A蠕变机制及强化机理。结果表明,随着Y、Ce含量的增加,ZL114A力学性能均呈先增大后减小的趋势,最优稀土添加量为0.3 wt.%,此时蠕变应力指数分别为3.52和3.88,蠕变过程均由位错粘滞性滑移主导。稀土元素在提升成分过冷的同时可形成异质形核核心,故α-Al晶粒得到一定细化,共晶硅相由碎片状转变为纤维状,原枝晶组织逐渐球化并向等轴晶发展。此外,稀土Y倾向点块状析出,而富Ce相则呈丝带状组织,二者主要分布于晶界处并部分固溶于合金基体。稀土原子起到钉扎作用阻碍位错运动进而强化晶界,并抑制高温下Mg2Si粗化分解以及Mg元素扩散造成的耐热性弱化。归因于稀土原子尺度差异造成的分布形态不同,Y变质效果相对更好。In order to further improve the mechanical properties of complex thin-walled aluminum alloy structural parts,especially the high temperature creep resistance,rare earth yttrium(Y)and cerium(Ce)were applied to modify ZL114A based on vacuum counter-pressure casting process.According to the experimental results of hardness,tensile properties,and creep strain,combined with the influence of rare earth elements on the evolution of the alloy microstructure,the creep mechanism and strengthening mechanism of the modified ZL114A alloy were revealed.The results indicate that the mechanical properties of alloy first increase and then decrease with the increase of Y and Ce,and the optimal addition is 0.3 wt.%.At this time,the creep stress indexes are 3.52 and 3.88 respectively,and the creep process is dominated by dislocation viscous slip.The rare earth atoms can improve the constitutional supercooling and as the core for heterogeneous nucleation which result in the grain refinement of a-Al.Meanwhile,the fragmented eutectic silicon phase changes into fibrous form and the original dendrites gradually spheroidized and developed into equiaxed crystal.Additionally,Y tends to precipitate in block form while the Ce rich phase presents as a ribbon structure,and the both elements are mainly distributed in the grain boundaries and partly dissolved in the alloy matrix.Therefore,the grain boundaries are strengthened due to the dislocation movement is hindered by the rare earth phase via pinning effect.Simultaneously,the weakening of heat resistance due to the coarsening and decomposition of Mg2Si and the diffusion of Mg can be inhibited by Y or Ce atoms at a high temperature.The modification effect of Y is relatively better because of the different of distribution morphology which is contributed to the scale difference in Y and Ce atoms.

关 键 词：蠕变机制 真空差压铸造 稀土变质 ZL114A 

分 类 号：TG292[金属学及工艺—铸造]