本文選題：5A06鋁合金 + 攪拌摩擦焊　； 參考：《太原科技大學(xué)》2017年碩士論文

【摘要】：攪拌摩擦焊技術(shù)是新型固相連接方法,可以有效解決傳統(tǒng)熔化焊接方法中易出現(xiàn)的熱裂紋、接頭熱影響區(qū)軟化及焊接變形等問題,為鋁合金等低熔點金屬的焊接提供了新方法。攪拌摩擦焊接過程復(fù)雜,而焊接溫度場能夠直觀地反映接頭溫度分布情況,通過溫度場的模擬研究可以進一步了解其焊接機制,對焊接參數(shù)的優(yōu)化及避免缺陷形成具有重要指導(dǎo)意義。本文首先建立了5A06鋁合金攪拌摩擦焊接過程的熱輸入模型,采用ANSYS有限元分析軟件對不同工藝參數(shù)下的焊接溫度場進行數(shù)值模擬,研究攪拌摩擦焊接過程溫度場分布規(guī)律以及攪拌頭轉(zhuǎn)速和焊接速度對溫度場的影響;通過對比模擬與試驗方法所測熱循環(huán)結(jié)果,驗證模型準確性;使用超景深顯微鏡觀察焊縫表面成形、內(nèi)部缺陷及焊核區(qū)微觀組織;利用顯微硬度計測試接頭橫截面硬度。得到如下結(jié)論:溫度場模擬結(jié)果顯示焊縫中心溫度低于軸肩邊緣,軸肩外側(cè)峰值溫度隨距焊縫中心距離增大而降低,焊縫兩側(cè)溫度場對稱分布。攪拌頭轉(zhuǎn)速影響峰值溫度,而焊接速度影響峰值溫度停留時間,轉(zhuǎn)速增大,峰值溫度升高,焊速增大,峰值溫度停留時間減少。試驗與模擬結(jié)果對比表明本文采用的熱量自適應(yīng)熱源模型能夠準確模擬焊接過程溫度場分布規(guī)律。對于12 mm厚鋁合金,最佳焊接參數(shù)為ω=220 r/min,v=8 cm/min,此時焊縫峰值溫度達到377°C,材料軟化程度及流動性較好,可以得到無缺陷、成形良好的焊縫。5A06鋁合金接頭顯微硬度與晶粒大小有關(guān),焊核區(qū)組織發(fā)生動態(tài)再結(jié)晶,轉(zhuǎn)變?yōu)榫鶆蚣毿〉容S晶,該區(qū)域硬度值與母材相比提高了約15%,達到84 HV。在接頭橫截面硬度呈“n”型分布,而焊縫厚度方向上晶粒尺寸與硬度無明顯變化。攪拌頭轉(zhuǎn)速提高,焊核區(qū)晶粒長大,顯微硬度有降低趨勢;焊接速度對晶粒尺寸及顯微硬度影響較小。
[Abstract]:Friction stir welding (FSW) is a new solid-phase bonding method, which can effectively solve the problems such as hot crack, heat affected zone softening and welding deformation, which can be used to weld low melting point metals such as aluminum alloy. The process of friction stir welding is complex, and the welding temperature field can directly reflect the temperature distribution of the joint. Through the simulation of the temperature field, the welding mechanism can be further understood. It is of great significance to optimize the welding parameters and avoid the formation of defects. In this paper, the heat input model of 5A06 aluminum alloy friction stir welding process is established, and the numerical simulation of welding temperature field under different process parameters is carried out by using ANSYS finite element analysis software. The distribution of temperature field in friction stir welding process and the effect of rotating speed and welding speed of stir head on temperature field were studied, and the accuracy of the model was verified by comparing the results of heat cycle measured by simulation and test methods. The weld surface forming, internal defects and microstructure of the nuke zone were observed by using the hyperfield depth microscope, and the cross section hardness of the joint was measured by microhardness meter. The results show that the center temperature of the weld is lower than the edge of the shaft shoulder and the peak temperature of the outside side of the shaft shoulder decreases with the increase of the distance from the center of the weld and the temperature field on both sides of the weld is symmetrically distributed. The rotating speed of the mixing head affects the peak temperature, while the welding speed affects the residence time of the peak temperature, the rotational speed increases, the peak temperature increases, the welding speed increases, and the peak temperature residence time decreases. The comparison of experimental and simulation results shows that the heat adaptive heat source model can accurately simulate the distribution of temperature field in welding process. For 12mm thick aluminum alloy, the optimum welding parameter is 蠅 220rmin / min / 8 cm / min, and the peak weld temperature reaches 377 擄C, the softening degree and fluidity of the material are good, and there is no defect. The microhardness of the well-formed weld. 5A06 aluminum alloy joint is related to the grain size. Dynamic recrystallization takes place in the microstructure of the nugget zone, which is transformed into uniform fine equiaxed crystal. Compared with the base metal, the hardness of the region is increased by about 15%, reaching 84 HV. The hardness of the cross section of the joint is "n" distributed, but the grain size and hardness have no obvious change in the direction of weld thickness. With the increase of the rotating speed of the mixing head, the grain size in the nugget region grows and the microhardness decreases, and the effect of welding speed on the grain size and microhardness is small.
【學(xué)位授予單位】：太原科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG453.9

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