(重慶大學(xué) 材料科學(xué)與工程學(xué)院，重慶 400044)
摘 要: 采用3種焊接速度(60、100和240 mm/min)對(duì)5 mm厚2024和7075鋁合金板材進(jìn)行攪拌摩擦對(duì)接焊試驗(yàn)，利用電子背散射衍射(EBSD)、硬度測(cè)試、拉伸試驗(yàn)、掃描電鏡和極化曲線(xiàn)測(cè)試對(duì)2024-7075異種鋁合金攪拌摩擦焊接頭的顯微組織、力學(xué)性能及腐蝕行為進(jìn)行了研究。結(jié)果表明：接頭焊核區(qū)發(fā)生動(dòng)態(tài)再結(jié)晶形成細(xì)小的等軸晶。沿板厚方向從軸肩區(qū)到底部區(qū)的平均晶粒尺寸依次減小，且焊核區(qū)不同位置處的平均晶粒尺寸均隨著焊接速度的增加而減小。異種接頭焊核區(qū)不同位置形成不同類(lèi)型的剪切織構(gòu)，其類(lèi)型隨焊接速度的改變而變化。接頭焊核區(qū)硬度呈現(xiàn)“W”型分布趨勢(shì)，且低于母材硬度。較低硬度值區(qū)域位于熱影響區(qū)，隨著焊接速度的降低，各區(qū)硬度值呈現(xiàn)下降的趨勢(shì)。接頭強(qiáng)度隨著焊接速度的增加而升高，焊接效率達(dá)到90.3%。與母材相比，焊接接頭焊核區(qū)的耐蝕性最差，這主要是由于異種焊接接頭焊核區(qū)發(fā)生了顯著的電偶腐蝕，導(dǎo)致較高的腐蝕電流密度。
關(guān)鍵字: 鋁合金；攪拌摩擦焊；微觀(guān)組織；力學(xué)性能；腐蝕性能
（College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China）
Abstract:2024 and 7075 aluminum alloys sheets of 5 mm thickness were used to conduct the friction stir butt welding tests by employing three welding speeds (60, 100 and 240 mm/min).The microstructure, mechanical properties and corrosion behavior of dissimilar friction stir welded 2024-7075 joints were studied by using electron backscatter diffraction (EBSD), hardness testing, tensile testing, scanning electron microscopy and polarization curves testing. The results show that the dynamical recrystallization occurs in the weld nugget to form fine equiaxed grains. The average grain size decreases from the shoulder region to the bottom region in the thickness direction, and the average grain size at different positions in the weld nugget decreases with the welding speed increasing. Different types of shear textures form at different locations in the weld nugget region of the dissimilar joint, and vary with the change of the welding speed. The hardness profile of the weld nugget zone shows a “W” type distribution trend, and its hardness value is lower than that of the base metals. The lower hardness value is located in the heat-affected zone. As the welding speed decreases, the hardness value of each zone shows a downward trend. The strength of the joint increases with the increase of the welding speed, and the welding efficiency reaches 90.3%. Comparing with the base metals, the weld nugget zone in the joint exhibits the worst corrosion resistance, mainly because of the significant galvanic corrosion in the weld nugget zone of the dissimilar weld joint, resulting in a higher corrosion current density.
Key words: aluminum alloy; friction stir welding; microstructure; mechanical property; corrosion property
