热处理对ZM6镁合金TIG焊后组织性能的影响Effect of heat treatment on microstructure and mechanical properties on TIG welded ZM6 magnesium alloy

采用钨极氩弧焊对ZM6铸造镁合金进行焊接，并对其进行了T6热处理，利用光学显微镜及扫描电镜对焊后及热处理后的焊接接头显微组织进行观察，对试样进行显微硬度和抗拉强度测试。结果表明：经过540 ℃固溶处理后，晶界处的化合物已基本固溶到基体。经200 ℃时效16 h后，出现3种析出相，并且焊缝及母材显微硬度均达到最大值，分别为85HV和81HV。热处理后拉伸试验断裂位置在熔合区附近，抗拉强度达到260 MPa，较未热处理的160 MPa有较大提高。热处理后拉伸断口形貌呈现出两个不同的区域，分别为解理和韧窝-解理混合断裂。

Tungsten inert gas welds were performed on cast ZM6 magnesium alloy and T6 heat treatment was carried out followed. The microstructures of welded joints and heat treated joints were investigated by optical and scanning electron microscopy. The microhardness and tensile strength were determined. The results demonstrate that after solution treatment at 540 ℃, the compounds in the grain boundary dissolve into the matrix. After aging at 200 ℃ for 16 h, three kinds of precipitates appear. The microhardness of weld seam and base metal reaches the maximum, which are 85HV and 81HV, respectively. The fracture locations of heat treated specimens in the tensile test are near the fusion zone. The heat treated specimens show the ultimate tensile strength of 260 MPa. Compared with not heat-treated of 160 MPa, the tensile strength of heat treated specimens is improved significantly. The tensile fracture of heat treated specimen surface shows two different areas, which are cleavage fracture and dimple-cleavage mixed fracture, respectively.

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