Friction stir processing (FSP) has confirmed its valuable contribution to refining microstructures and the improvement of mechanical properties for Mg-Al alloys. Reference papers illustrate that post-processing aging treatments enhance hardness, but with the application of a solution heat treatment prior to FSP. In this work, aging was performed at two different temperatures (170 and 300 °C) directly on friction stir processed samples of AZ91 produced using high pressure die casting (HPDC). High rotational speeds of the tools (2500 and 3000 rpm) increases the heat input and the temperature of the plates during the process up to 270 °C. Vickers microhardness (HV) increased by 15–20% in the nugget, compared to the as FSPed condition; moreover, a greater homogeneity of hardness values was found at the higher aging temperature used. The β-Mg₁₇Al₁₂ precipitates are randomly distributed inside grains of the stirred area, while in the thermomechanical affected zone (TMAZ) they have grown in a network similar to the old eutectic. A preliminary investigation of FSPed samples deformed at 300 °C found that an equivalent hardness increase is achievable using hot deformation due to dynamic precipitation; to find local homogeneity in hardness, it is worth performing a final aging.

中文翻译：

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高转速摩擦搅拌处理对HPDC Mg9Al1Zn时效的影响

搅拌摩擦加工（FSP）已经证实了其对精炼微结构和改善Mg-Al合金机械性能的宝贵贡献。参考文件表明，后处理的时效处理可以提高硬度，但是要在FSP之前进行固溶热处理。在这项工作中，老化是在两个不同的温度（170和300°C）下直接对使用高压压铸（HPDC）生产的AZ91进行摩擦搅拌处理的样品进行的。工具的高转速（2500和3000 rpm）在过程中将热量输入和板的温度提高到270°C。与FSPed条件相比，金块中的维氏显微硬度（HV）提高了15–20％；此外，在较高的时效温度下发现硬度值的均一性更高。β-镁₁₇ Al ₁₂沉淀物随机分布在搅拌区的晶粒内，而在热机械影响区（TMAZ）中，它们以类似于旧共晶的网络生长。对在300°C下变形的FSPed样品进行的初步研究发现，由于动态沉淀而产生的热变形可实现相当的硬度增加。为了找到硬度的局部均匀性，值得进行最后的时效处理。