熱處理對ZM6鎂合金TIG焊后組織性能的影響Effect of heat treatment on microstructure and mechanical properties on TIG welded ZM6 magnesium alloy

采用鎢極氬弧焊對ZM6鑄造鎂合金進行焊接，并對其進行了T6熱處理，利用光學顯微鏡及掃描電鏡對焊后及熱處理后的焊接接頭顯微組織進行觀察，對試樣進行顯微硬度和抗拉強度測試。結果表明：經過540 ℃固溶處理后，晶界處的化合物已基本固溶到基體。經200 ℃時效16 h后，出現3種析出相，并且焊縫及母材顯微硬度均達到最大值，分別為85HV和81HV。熱處理后拉伸試驗斷裂位置在熔合區附近，抗拉強度達到260 MPa，較未熱處理的160 MPa有較大提高。熱處理后拉伸斷口形貌呈現出兩個不同的區域，分別為解理和韌窩-解理混合斷裂。

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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