在空气中和水下对AZ91镁合金铸造板材进行搅拌摩擦加工,并对材料的微观组织和力学性能进行了分析测试.研究结果表明:由于水的强制冷却作用,水下搅拌摩擦加工板的搅拌区面积小于空气中加工板,两种板材搅拌区的微观组织均得到了显著细化,平均晶粒尺寸分别为1.9μm和3.5μm；热机影响区均形成了纤维状组织,且水下搅拌摩擦加工板的组织更为细小；空气中加工板的热影响区出现了组织粗化,而水下加工板的热影响区的晶粒尺寸与母材相当.两种加工工艺均使第二相β-Mg17Al12由原始铸态组织中连续网状变为颗粒状.由于水下加工板的组织更为细小,其硬度、抗拉强度和伸长率较空气中搅拌摩擦加工板高.%Normal and submerged friction stir processing ( SFSP) were applied to prepare fine-grained AZ91 alloy, and microstructure and mechanical properties of the processed materials were investigated. The results show that owing to cooling water, the stir zone ( SZ) area of SFSP is smaller than that of normal FSP, and microstructures are significantly refined, which the average grain sizes were 1.9μm and 3.5μm respectively. The fibrous structure in the thermal-mechanically affected zone (TMAZ) , but the average grain size of SFSP was finer. Microstructure of the normal FSP coarsened in the heat affected zone ( HAZ) , while the grain size of the SFSP plate was almost equal to that of the base material ( BM ). The second phase β-Mg17 Al12 of both two processes were changed from network into particles in SZ. The hardness, tensile strength and elongation of SFSP material were higher than those of normal FSP.
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