發(fā)布時間：2019-05-17 19:09

【摘要】：ZK60鎂合金具有較好的力學(xué)性能,但其價格較高,而MB8鎂合金具有優(yōu)異的耐腐蝕性能,采用MB8鎂合金代替ZK60鎂合金可提高接頭抗腐蝕能力和降低成本。為此,本文對ZK60和MB8鎂合金薄板分別進(jìn)行同材質(zhì)及異材質(zhì)的光纖激光焊接工藝研究,分析工藝參數(shù)對焊接接頭的宏觀形貌、顯微組織、力學(xué)性能、斷裂位置、斷口形貌的影響,并采用滲透檢測方法檢驗接頭表面缺陷。試驗結(jié)果表明,同材質(zhì)ZK60鎂合金焊縫組織為細(xì)小等軸晶,主要由α-Mg基體和MgZn2相構(gòu)成;同材質(zhì)MB8鎂合金焊縫組織為等軸晶和柱狀樹枝晶,主要由α-Mg基體和Mn相構(gòu)成;ZK60與MB8異材質(zhì)鎂合金焊縫組織為等軸晶和柱狀樹枝晶,主要由α-Mg基體和MgZn2相構(gòu)成。經(jīng)滲透檢測均未發(fā)現(xiàn)表面缺陷,焊接接頭成型良好,當(dāng)工藝參數(shù)不合適時,有少量氣孔存在。對于同材質(zhì)ZK60鎂合金焊接接頭,抗拉強(qiáng)度最高可達(dá)到母材的92.1%,熔合線附近顯微硬度較低,斷裂多發(fā)生在焊縫中心至熔合線附近區(qū)域內(nèi),斷口呈現(xiàn)韌性斷裂為主導(dǎo)的混合斷裂形貌;對于同材質(zhì)MB8鎂合金焊接接頭,抗拉強(qiáng)度最高可達(dá)到母材的83.1%,熔合線附近顯微硬度較低,斷裂多發(fā)生在焊縫中心附近,斷口呈現(xiàn)準(zhǔn)解理斷裂形貌。對于ZK60與MB8異材質(zhì)鎂合金焊接接頭,其抗拉強(qiáng)度均顯著大于同材質(zhì)MB8鎂合金焊接接頭,且在較寬的工藝參數(shù)范圍內(nèi),接頭抗拉強(qiáng)度大于MB8母材抗拉強(qiáng)度。MB8側(cè)熔合線附近顯微硬度較低,斷裂均發(fā)生在焊縫中心至MB8母材區(qū)域內(nèi),斷口呈現(xiàn)準(zhǔn)解理斷裂形貌。
[Abstract]:ZK60 magnesium alloy has good mechanical properties, but its price is high, while MB8 magnesium alloy has excellent corrosion resistance. Using MB8 magnesium alloy instead of ZK60 magnesium alloy can improve the corrosion resistance and reduce the cost of the joint. In this paper, the optical fiber laser welding process of ZK60 and MB8 magnesium alloy sheets with the same material and different material is studied, and the effects of process parameters on the macroscopic morphology, microstructure, mechanical properties, fracture position and fracture morphology of the welded joints are analyzed. The surface defects of the joint were examined by osmotic detection method. The experimental results show that the weld microstructure of the same material ZK60 magnesium alloy is fine equiaxed crystal, which is mainly composed of 偽-Mg matrix and MgZn2 phase, and the weld microstructure of the same material MB8 magnesium alloy is isometric crystal and columnar dendritic crystal, which is mainly composed of 偽-Mg matrix and Mn phase. The weld microstructure of ZK60 and MB8 magnesium alloy is equiaxed crystal and columnar dendrite, which is mainly composed of 偽-Mg matrix and MgZn2 phase. No surface defects were found by osmotic test, the welded joints were well formed, and a small number of pores existed when the process parameters were not timely. For the welded joints of ZK60 magnesium alloy of the same material, the highest tensile strength can reach 92.1% of that of the base metal, the microhardness near the fusion line is low, and most of the fractures occur in the area from the center of the weld to the near the fusion line. The fracture surface shows a mixed fracture morphology dominated by ductile fracture. For the welded joints of MB8 magnesium alloy of the same material, the highest tensile strength can reach 83.1% of that of the base metal, the microhardness near the fusion line is low, the fracture mostly occurs near the center of the weld, and the fracture surface shows quasi-cleavage fracture morphology. For the welded joint of ZK60 and MB8 magnesium alloy, the tensile strength of the welded joint is significantly higher than that of the same material MB8 magnesium alloy welded joint, and in a wide range of process parameters, The tensile strength of the joint is higher than that of the MB8 base metal. The microhardness near the fusion line of MB8 side is lower, the fracture occurs in the area from the center of the weld to the MB8 base metal, and the fracture surface shows quasi-cleavage fracture morphology.
【學(xué)位授予單位】：陜西理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG456.7

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