【作者】 王冰；

【导师】 张忠明；

【作者基本信息】 西安理工大学 ， 材料加工工程， 2007， 硕士

【摘要】 本文采用热挤压法使用自制挤压装置,对AZ31、AZ91镁合金焊丝成形工艺进行了实验研究。确定其成形工艺参数,如:挤压温度、挤压速度和挤压力等。成功制备出了AZ31、AZ91镁合金焊丝,并分析了焊丝的组织与性能。同时,进行了AZ31、AZ91镁合金焊丝的填丝TIG焊接,获得了成型良好的焊接接头。制备表面光洁、性能良好的φ3mm和φ4mm AZ31、AZ91镁合金焊丝的挤压工艺为:挤压温度:420℃;挤压力:9×10⁵N;出丝速度:0.8m/min¹m/min。当挤压温度过低时,焊丝表面会出现划伤和起皮现象;当挤压温度过高、冲头压力过大时,焊丝表面会出现大量热裂纹。热挤压法制备的镁合金焊丝晶粒细小,力学性能良好。其中,AZ31镁合金焊丝晶粒尺寸为5μm¹5μm,AZ91镁合金焊丝晶粒尺寸为10μm³0μm。与铸态相比,抗拉强度均提高了25%左右,延伸率提高1倍以上,AZ31镁合金焊丝硬度提升约85%;AZ91镁合金焊丝硬度提高约26.8%。使用实验制备的镁合金焊丝（AZ31焊丝和AZ91焊丝）焊接AZ31板材。随焊丝含铝量的提高,焊缝区的微观组织变化明显,晶粒尺寸趋于减小,同时晶界上β-Mg₁₇Al₁₂相逐渐增多。采用AZ91焊丝时,β-Mg₁₇Al₁₂相不连续的分布在晶界周围。与母材相比,焊缝区、热影响区和近焊缝区的共晶β-Mg₁₇Al₁₂相多。镁合金焊丝焊接AZ31镁合金板材可以获得较高的接头强度。AZ31和AZ91镁合金焊丝焊接AZ31板材,接头抗拉强度分别为210MPa和187MPa,是AZ31母材强度的83%和74%;接头延伸率分别为2.5%和2.1%。AZ91镁合金焊丝的接头硬度普遍高于AZ31合金焊丝。两种情况下焊接接头的硬度分布规律相同,均是焊缝区硬度最高,母材硬度次之,热影响区硬度最低。更多还原

【Abstract】 The technology for preparation of AZ31,AZ91 magnesium alloys welding wire by hot extrusion process was studied. The AZ31,AZ91 magnesium alloys welding wires were successfully prepared after the confirmation of the technological parameters, such as: extrusion temperature, extrusion speed and extrusion force, etc. Microstructure and mechanical properties of magnesium alloys welding wire were also analyzed. The nice bonding of welding joint was obtained by using TIG with AZ31,AZ91 magnesium alloys filler wire under rational welding condition. AZ31 and AZ91 magnesium alloys welding wire withφ3mm andφ4mm can be prepared by hot-extrusion when extrusion temperature is 420℃, extrusion speed is 0.8m/min～1m/min and extrusion force is 9×10⁵N. The welding wires have smooth and bright surface and good performance. Scratched and rough surface appeared when the extrusion temperature is too low, while hot crack emerges when the extrusion temperature and extrusion force are too high.The microstructure of hot extruded AZ31,AZ91 magnesium alloys welding wire were refined. Grain size of AZ31 was 5μm¹5μm, grain size of AZ91 was 10μm～30μm. Compared with as-cast AZ31 alloy, the tensile strength of the wires increases about 25%, elongation doubles, the hardness of AZ31 promotes by 85%. and the hardness of AZ91 promoted about 26.8%.The grain size decreased and theβ-Mg₁₇Al₁₂ phase increased at the grain boundary in the weld joint when the AZ31 welding wire was used to weld AZ31 plates by TIG.. While AZ31 bases was welded with AZ91 welding wire, theβ-Mg₁₇Al₁₂ phases in the weld joint discontinuously surrounded the grain boundary and there are moreβ-Mg₁₇Al₁₂ phases in weld zone and heat affected zone than in the base.The higher welded joint strength was obtained when magnesium alloys welding wire wasused for AZ31 base welding. When using AZ31 magnesium alloys welding wire, the tensile strength of welded joint increased by 83%, and reached to 210MPa. When using AZ91 magnesium alloys welding wire, tensile strength of welded joint was 187MPa and increase by 74%. The elongation of AZ31 welded joint using AZ31 and AZ91 magnesium alloys welding wire were 2.5% and 2.1%, respectively. The hardness of welded joint using AZ91 magnesium alloys welding wire is higher than that of using AZ91. The hardness variation in weld joints with different weld filler is the same, that is hardness in weld zone was highest, and the hardness in the base was higher than that in the heat affected zone.更多还原