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首页> 外文期刊>Journal of Materials Science >Precipitation hardening of Zr-modified Mg-Ca-Zn alloy
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Precipitation hardening of Zr-modified Mg-Ca-Zn alloy

机译：Zr改性Mg-Ca-Zn合金的沉淀硬化

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The microstructure and mechanical properties of Mg-Ca-Zn alloys with 1 wt.% Zr were investigated in as-cast and heat-treated conditions. A substantial decrease in grain size (from 65 A mu m for the Mg-Ca-Zn base alloy to 22 A mu m) was observed. The alloy was solution treated at 410 A degrees C for up to 96 h followed by aging at 175 A degrees C for up to 24 h. Conventional techniques, X-ray diffraction, EM + EDS, and TEM were used to characterize the microstructure of the alloy. The microstructure obtained after heat treatment had equiaxed grains with evenly distributed binary phase Zn2Zr. The binary Mg2Ca and ternary Mg2Ca6Zn3 phases were identified in the matrix and at grain boundaries surrounded by precipitate-depleted zones (PDZs). The thermal stability of the Zr-modified alloys was examined by microhardness measurements conducted after prolonged exposures of the alloys to elevated temperatures. It was found that Zr is a structure-stabilizing factor. Its influence was associated with the formation of Zn2Zr phase that does not undergo coarsening at the elevated temperatures used (due to the low diffusivity of Zr). The nanoscale mechanical properties of grain boundary PDZs were analyzed using combined nanoindentation and atomic force microscopy. These mechanical properties were then correlated to the composition and precipitate distribution in PDZs. An increase in the solution treatment duration from 10 to 96 h at 410 A degrees C resulted in expansion of PDZs from similar to 0.75 to similar to 3 A mu m, while the following aging at 175 A degrees C for up to 24 h did not lead to a detectable change in PDZs. The analysis indicates that the lowest hardness was found in the region where Zn2Zr precipitates density was low, regardless of the solute concentration.
机译：在铸造和热处理条件下研究了Zr为1 wt％的Mg-Ca-Zn合金的显微组织和力学性能。观察到晶粒尺寸显着减小（从Mg-Ca-Zn基合金的65 Aμm降至22 Aμm）。合金在410 A的温度下固溶处理长达96小时，然后在175 A的温度下老化24小时。常规技术，X射线衍射，EM + EDS和TEM用于表征合金的微观结构。热处理后获得的显微组织具有等轴晶，其二元相Zn2Zr均匀分布。 Mg2Ca和Mg2Ca6Zn3三元相在基体中和被析出物贫化区（PDZs）包围的晶界处被识别。 Zr改性合金的热稳定性通过将合金长时间暴露在高温下进行的显微硬度测量来检查。发现Zr是结构稳定因子。其影响与Zn2Zr相的形成有关，该相在所使用的高温下不会发生粗化（由于Zr的低扩散性）。结合纳米压痕和原子力显微镜分析了晶界PDZs的纳米级力学性能。然后将这些机械性能与PDZ中的成分和沉淀物分布相关。在410 A的温度下，固溶处理时间从10 h增加到96 h，导致PDZ从类似的0.75扩展到3 Aμm，而随后在175 A的温度下长达24 h的老化没有导致PDZ发生可检测的变化。分析表明，无论溶质浓度如何，在Zn2Zr析出密度低的区域发现最低的硬度。

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