本文關(guān)鍵詞： 雙軸肩攪拌摩擦焊 攪拌頭設(shè)計(jì) 鋁合金 微觀組織　出處：《南昌航空大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：雙軸肩攪拌摩擦焊技術(shù)(Bobbin Tool Friction Stir Welding,BTFSW)作為攪拌摩擦焊領(lǐng)域的拓展技術(shù),利用下軸肩代替背部剛性墊板,大大減小了垂直方向上的鍛壓力,降低了裝夾要求及夾具成本,同時(shí)消除了根部未焊透問題。因此在工程實(shí)踐中有很高的應(yīng)用價(jià)值。本文針對(duì)4mm厚6061-T6鋁合金設(shè)計(jì)了不同的軸肩形貌及攪拌針形貌,并進(jìn)行雙軸肩攪拌摩擦焊試驗(yàn),研究了攪拌頭形貌和焊接工藝參數(shù)對(duì)接頭成形及抗拉強(qiáng)度的影響。分析了雙軸肩攪拌摩擦焊接頭各區(qū)域組織特點(diǎn),并總結(jié)接頭中容易出現(xiàn)的缺陷類型及缺陷對(duì)接頭抗拉強(qiáng)度的影響。主要的研究成果如下:在攪拌頭為平面軸肩和圓柱形攪拌針不變的情況下,焊接接頭隨著上軸肩下壓量的減小,接頭上表面飛邊量先減小后增加,下表面飛邊量逐漸增加;隨著旋轉(zhuǎn)速度的增加,接頭表面易出現(xiàn)魚鱗紋且逐漸由不均勻變得均勻;隨著焊接速度增加,焊接接頭上表面后退側(cè)飛邊從無(wú)到有,且飛邊量增加;同時(shí)上下表面接頭魚鱗紋逐漸變得均勻。根據(jù)雙軸肩攪拌摩擦焊接頭中微觀組織特點(diǎn),接頭可分為母材區(qū)(BM)、熱影響區(qū)(HAZ)、熱力影響區(qū)(TAMZ)及焊核區(qū)(WNZ)四個(gè)區(qū)域,其中焊核區(qū)為等軸晶粒,熱力影響區(qū)晶粒為發(fā)生塑性變形的板條狀晶粒,熱影響區(qū)為發(fā)生粗化的板條狀晶粒。通過(guò)正交試驗(yàn)發(fā)現(xiàn)各因素對(duì)接頭宏觀形貌影響的主次順序依次為:軸肩形貌、旋轉(zhuǎn)速度、軸肩下壓量、攪拌針形貌、焊接速度。各因素對(duì)接頭抗拉強(qiáng)度影響的主次順序依次為:軸肩下壓量、軸肩形貌、攪拌針形貌、旋轉(zhuǎn)速度、焊接速度。焊接頭容易出現(xiàn)的缺陷類型分別為孔洞缺陷、弱結(jié)合缺陷、S線缺陷;其中孔洞缺陷易出現(xiàn)在前進(jìn)側(cè)WNZ與TMAZ交界處和WNZ偏向后退側(cè)區(qū)域,弱結(jié)合缺陷易出現(xiàn)在前進(jìn)側(cè)WNZ與TMAZ交界處,S線缺陷易出現(xiàn)在WNZ偏向后退側(cè)區(qū)域。通過(guò)對(duì)比發(fā)現(xiàn)接頭中S線缺陷區(qū)域的冶金結(jié)合程度不同,如果該區(qū)域冶金結(jié)合程度較差,則可能會(huì)影響接頭的抗拉強(qiáng)度,如果該區(qū)域的冶金結(jié)合程度較好,則對(duì)接頭的抗拉強(qiáng)度沒有影響。另外S線缺陷的形狀也會(huì)影響接頭的抗拉強(qiáng)度。正交試驗(yàn)優(yōu)化結(jié)果表明:當(dāng)攪拌頭形貌為內(nèi)凹帶螺旋凹槽軸肩形貌和三平面帶右螺紋攪拌針形貌,工藝參數(shù)為上軸肩下壓量0.05mm,下軸肩下壓量0.15mm,焊接速度120mm·min-1,旋轉(zhuǎn)速度520r·min-1時(shí)焊接接頭抗拉強(qiáng)度最高,接頭抗拉強(qiáng)度為230.36 MPa。
[Abstract]:The technology of bobbin Tool Friction Stir welding BTFSWs is used to expand the field of friction stir welding. The lower shaft shoulder is used to replace the back rigid pad, which greatly reduces the forging pressure in the vertical direction, the clamping requirement and the fixture cost. At the same time, the problem of root penetration is eliminated, so it has high application value in engineering practice. In this paper, different shaft-shoulder morphology and stirring needle morphology are designed for 6061-T6 aluminum alloy with 4mm thickness. The effects of joint morphology and welding parameters on the joint forming and tensile strength were studied. The microstructure characteristics of the joint were analyzed. The main research results are as follows: under the condition that the mixing head is flat shaft shoulder and cylindrical stirring needle is unchanged. With the decrease of shoulder pressure, the upper surface flange decreases first and then increases, and the lower surface flange increases gradually. With the increase of rotation speed, the surface of the joint is easy to appear scales and gradually change from uneven to uniform. With the increase of welding speed, the flange of the receding side of the upper surface of the welded joint starts from nothing to existence, and the amount of flying edge increases. At the same time, the upper and lower surface joints gradually become uniform. According to the microstructure characteristics of friction stir welding joints, the joints can be divided into base metal area (BMN), heat affected zone (HAZ). Tam Z) and WNZ are four regions, in which the nugget zone is equiaxed grain, and the thermal effect zone grain is the strip grain of plastic deformation. The main and secondary order of the influence of various factors on the macroscopic morphology of the joint is as follows: axial shoulder morphology, rotation speed, axial shoulder pressure, stirring needle morphology. Welding speed. The main and secondary order of the influence of each factor on the tensile strength of the joint is as follows: the axial shoulder pressure, the shaft-shoulder morphology, the stirring needle morphology, the rotation speed. Welding speed. The defect types of welding joint are hole defect, weak joint defect and S-line defect respectively. The hole defects are easy to appear at the junction of WNZ and TMAZ on the forward side and on the backward side of the WNZ bias, and the weak binding defects at the junction of WNZ and TMAZ on the forward side. S-line defects are prone to occur in the receding region of WNZ bias. It is found that the metallurgical bonding degree of S-line defect region in the joint is different, if the metallurgical bonding degree is poor in this area. The tensile strength of the joint may be affected if the metallurgical bonding in the region is good. In addition, the shape of S-line defects will also affect the tensile strength of the joint. The orthogonal test results show that:. The shape of the mixing head is the shape of the shaft shoulder of the inner concave spiral groove and the shape of the stirring needle with the right thread of the three-plane belt. The technological parameters are as follows: the pressure of the upper shoulder is 0.05mm, the pressure of the lower shoulder is 0.15mm, and the welding speed is 120mm 路min-1. The tensile strength of welded joints is the highest at 520r 路min-1 rotation speed, and the tensile strength of welded joints is 230.36 MPa.
【學(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG453.9

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