不同冷却介质下多道次搅拌摩擦加工对 AZ91镁合金组织和性能影响

对铸态 AZ91镁合金板进行了三种不同冷却条件下的多道次搅拌摩擦加工，即两次空气、一次空气和一次水下、两次水下的搅拌摩擦加工，并对其组织和力学性能进行了研究。研究结果表明：在多道次搅拌摩擦加工过程中，剧烈的塑性变形使搅拌区内呈网状的第二相β-Mg17 Al12显著破碎变成细小颗粒状，搅拌区的微观组织均得到了显著细化，三种不同冷却条件下样品的平均晶粒尺寸分别为5．8μm，1．4μm 和0．8～1μm；两次水下加工的组织更为细小，其显微硬度、抗拉强度和延伸率较其他两种冷却条件下多道次搅拌摩擦加工样品的高，分别为94．7 HV，355．5 MPa 和31．5％。

Microstructure and Properties of AZ91 Magnesium Alloy Prepared by Multi-pass Friction Stir Processing under Different Cooling Conditions

Multi-pass friction stir processes (MP-FSP)were conducted on cast AZ91 magnesium alloy plate under three different types of cooling condition,including two passes in air,one pass in air and one pass in water,and two passes in water.And microstructure and mechanical properties of the experimental materials were studied.The results show that the second phase,β-Mg17 Al12 ,is changed into particles because of the severe plastic deformation during MP-FSP.Meanwhile,the microstructures in stir zone are refined signifi-cantly and the average grain sizes are 5.8 μm,1 .4 μm and 0.8-1 μm respectively.Due to its finer microstructure,the microhardness, tensile strength and elongation of the specimen processed under two passes in water are 94.7 HV,355.5 MPa and 31 .5 %,which are higher than the other two different cooling conditions.