發(fā)布時間：2018-05-08 02:26

  本文選題：激光對接焊 + 填粉��； 參考：《湖南大學》2015年碩士論文

【摘要】：鋼鋁異種材料焊接結構高強輕質等方面的綜合優(yōu)勢使其在汽車制造領域應用越來越廣泛,有利于汽車輕量化的發(fā)展。但二者物理化學性質差異明顯,相互固溶度低,極易生成Fe-Al脆性金屬間化合物,嚴重影響焊接接頭的力學性能。因此,鋼鋁異種合金連接成為焊接領域的難點。本文選取第三代車身用鋼TG-1和5251鋁合金為研究對象,從焊接工藝參數(shù)控制和合金元素作用機制兩方面入手,率先運用同軸送粉技術實現(xiàn)鋼鋁異種材料的激光對接熔釬焊接,開展鋼鋁激光熔釬焊特性和界面行為研究,利用金相顯微鏡、掃描電鏡、微區(qū)X射線衍射、拉伸試驗機、納米壓痕等手段系統(tǒng)分析了接頭的金相組織、元素分布、界面主要物相、斷口形貌和接頭力學性能等,以期為實現(xiàn)高質量鋼鋁異種材料激光熔釬焊接提供理論依據(jù)和技術支持。首先,通過填加AlSi12、AlSi5、Al Cu5、Zn Al15合金粉末,分析接頭特性,研究不同元素對焊件表面形態(tài)、微觀界面層結構特征的影響,并評定不同粉末填加下的接頭力學性能。優(yōu)化的工藝參數(shù)下,均獲得有效的鋼鋁熔釬焊接連接。Si元素作用下,界面層主要生成Fe_4Al_(13)、FeAl_3Si及Fe_(0.905)Si_(0.0905)等化合物,Fe-Si相及Fe-Al-Si相降低了接頭脆性;Cu元素在界面層處未形成Al-Cu及Fe-Al-Cu相,但固溶在析出的Fe_4Al_(13)中,通過降低Fe、Al原子擴散速率影響界面反應;Zn元素固溶在Fe_4Al_(13)中,沒有改變Fe-Al相的晶體結構,卻改善了其性能。AlSi12合金粉末作用下接頭抗拉強度最高,為128.3 MPa,約為鋁合金母材強度的68%,說明Si元素含量的增加有利于降低界面層硬度。綜合焊縫成形性、界面層的微觀組織及接頭力學性能,AlSi12粉末作用效果最好。其次,在工藝方面,研究界面層厚度、工藝參數(shù)及接頭強度之間的關系,尋求金屬間界面層相關控制機理。界面層厚度與各工藝參數(shù)存在一定聯(lián)系,需要合理匹配焊接工藝參數(shù),將界面層厚度控制在10μm范圍內。接頭的抗拉強度與界面層厚度之間雖暫時未發(fā)現(xiàn)明顯的線性及函數(shù)相關性,但有效的釬接接頭界面層厚度大部分集中在此范圍。接頭強度在有效激光功率范圍內,呈現(xiàn)先增長后降低的趨勢,且隨焊接速度的增加而逐漸增大。而在有效間隙范圍內,接頭強度隨對接間隙的增大逐漸降低。論文研究結果對開發(fā)異種金屬連接新工藝和促進輕量化結構應用具有一定的理論意義和應用價值。
[Abstract]:The comprehensive advantages of steel and aluminum dissimilar materials in welding structure, such as high strength and light weight, make it more and more widely used in the field of automobile manufacturing, which is beneficial to the development of automobile lightweight. However, the physical and chemical properties of the two are obviously different, and the mutual solution is low, so it is easy to form Fe-Al brittle intermetallic compounds, which seriously affects the mechanical properties of welded joints. Therefore, the joint of steel and aluminum dissimilar alloys has become a difficult point in welding field. In this paper, the third generation of body steel TG-1 and 5251 aluminum alloy are selected as the research objects. Starting from the control of welding process parameters and the mechanism of alloy element action, the coaxial powder feeding technology is first used to realize laser butt welding of dissimilar materials of steel and aluminum. The characteristics and interface behavior of laser brazing of steel and aluminum were studied. The metallographic structure and element distribution of the joint were systematically analyzed by means of metallographic microscope, scanning electron microscope, microzone X-ray diffraction, tensile testing machine and nano-indentation. The main interface phase, fracture morphology and mechanical properties of joints are expected to provide theoretical basis and technical support for the realization of laser welding of high quality steel and aluminum dissimilar materials. First of all, by adding AlSi12AlSi5AlSi5AlCu5Cn-Zn Al15 alloy powder, the joint characteristics were analyzed, the effects of different elements on the surface morphology and microstructure of the interface layer were studied, and the mechanical properties of the welded joints were evaluated by adding different powders. Under the optimized technological parameters, under the action of effective steel and aluminum welding joining. Si element, the interface layer mainly produces Fe4AlAl1 / 13Sh / FeAl3Si and Feal 0.905SiP / Fe-Al-Si phases, which reduce the brittleness of the joints. No Al-Cu and Fe-Al-Cu phases have been formed at the interface layer of the interface layer, and the results show that there are no Al-Cu and Fe-Al-Cu phases in the interfacial layer of the interface layer, so that the Fe Si phase and the Fe-Al-Si phase can be reduced by the addition of Fe Si phase and Fe-Al-Si phase in the interface layer. But in the precipitated Fe4AlSi-13), the solid solution of Zn element in the interface reaction by decreasing the diffusion rate of Fenal atoms in the Fe4AlSi-13) did not change the crystal structure of the Fe-Al phase, but improved its properties. The tensile strength of the joints under the action of the powder. AlSi12 was the highest. 128.3 MPA, about 68% of the strength of the aluminum alloy base metal, indicating that the increase of Si content is beneficial to the reduction of the hardness of the interfacial layer. The effect of AlSi12 powder on the microstructure and mechanical properties of the interfacial layer is the best. Secondly, the relationship among intermetallic layer thickness, process parameters and joint strength is studied, and the control mechanism of intermetallic interfacial layer is sought. The thickness of the interfacial layer is related to the process parameters. It is necessary to match the welding parameters reasonably and control the thickness of the interfacial layer in the range of 10 渭 m. Although there is no obvious linear and functional correlation between the tensile strength and the thickness of the interface layer, the effective interfacial layer thickness of the brazing joint is mostly concentrated in this range. In the range of effective laser power, the joint strength increases first and then decreases, and increases gradually with the increase of welding speed. However, in the range of effective clearance, the joint strength decreases with the increase of butt clearance. The results of this paper have certain theoretical significance and application value for developing new technology of dissimilar metal joining and promoting the application of lightweight structure.
【學位授予單位】：湖南大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TG457.1

【參考文獻】

相關期刊論文 前10條

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本文編號：1859554