机械合金化和热处理对高熵合金MgTiVCrNi微观组织演化和相结构的影响

Effect of Mechanical Alloying and Treatment on the Microstructure Evolution and Phase Structure of the Entropy Alloys MgTiVCrNi

通过机械合金化球磨反应制备了含不同组元数和等摩尔比组成的合金体系Mg-TiV-Cr-Ni,利用XRD、EDS能谱分析、TEM以及DSC/TG热分析了组元数及热处理对合金球磨产物微观组织和相形成规律的影响.结果表明：经20h球磨后,二元合金Mg-Cr、Mg-V与MgTi体系几乎不发生合金化反应,随合金主组元数的增加,高混合熵效应可促进多元合金组元之间的相互反应和固溶,其中五元高熵合金Mg Ti VCr Ni球磨产物可形成富Mg的非晶相与贫Mg的纳米晶BCC型相.经400-600℃热处理后,合金Mg Ti VCr Ni球磨组织中的非晶相经晶化后转变为新的和贫Mg的BCC型结构相,当温度提高至600℃时,残余的金属Cr逐渐在BCC型相中固溶,最终形成稳定的单相BCC型固溶体.球磨高熵合金Mg Ti VCr Ni中形成的BCC型固溶体结构具有较高的热稳定性.

The equiatomic multi-components Mg-Ti-V-Cr-Ni high-entropy alloys were synthesized by mechanical alloying（MA）. By using XRD analysis, EDS mapping, SEM, TEM and thermal analysis, the effect of ball milling and subsequent annealing on the phase microstructure evolution of the milled alloys powders were investigated. The results showed that after high energy ball milling for 20 h no crystalline solid solutions and compounds formed for binary immiscible system Mg-V and Mg-Cr, but the reaction and solid solubility between the multi-components could be evidently enhanced with increase of the equiatomic multicomponent number, and thus an amorphous phase richen in Mg and nanocrystalline with BCC type were formed in milled Mg Ti VCr Ni alloy. The amorphous phase transformed to Mg-free nanocrystalline phase with BCC type when the milled Mg Ti VCr Ni alloy was annealed at 400-600o C for 1h.With increase of the annealing temperature, the residual metal Cr is gradually dissolved into the BCC type solution and finally formed a stable and single BCC solid solution. The BCC type solution formed in the milled Mg Ti VCr Ni alloy exhibited a good thermal stability.