發(fā)布時(shí)間：2018-05-02 17:04

  本文選題：攪拌摩擦焊 + 軸肩形貌��； 參考：《南昌航空大學(xué)》2015年碩士論文

【摘要】：本課題設(shè)計(jì)了內(nèi)凹型、小通道凹型、大通道凹型、側(cè)通道凹型和外凸型五種軸肩形貌的攪拌頭,選用鋁箔作標(biāo)識(shí)材料,采用水平、縱向和橫向鑲嵌的方法將鋁箔與2A12鋁合金薄板進(jìn)行攪拌摩擦焊的疊層試驗(yàn),通過觀察焊縫三維截面的標(biāo)示材料形態(tài),研究軸肩形貌對(duì)焊縫金屬塑性流動(dòng)的影響,總結(jié)其影響規(guī)律,建立不同軸肩形貌的攪拌頭下獲得的焊縫金屬三維流動(dòng)物理模型,并分析塑性流動(dòng)對(duì)組織性能的影響,為控制攪拌摩擦焊縫成形提供實(shí)踐依據(jù)。研究結(jié)果表明:軸肩下方金屬受到的作用力發(fā)生變化,影響焊縫金屬的塑性流動(dòng)形態(tài),進(jìn)而改變焊縫橫截面的形貌。增加軸肩鍛壓力可增大塑化金屬層之間的摩擦力,有利于焊縫金屬的塑性流動(dòng),減少了疏松缺陷,提高了焊縫的致密性。采用小通道凹槽軸肩的攪拌頭焊接,可增大軸肩作用區(qū)內(nèi)的塑化金屬流動(dòng)速度;同時(shí)增強(qiáng)了“抽吸-擠壓”效應(yīng),單位時(shí)間內(nèi)軸肩驅(qū)動(dòng)至攪拌針作用區(qū)及焊縫下部的塑化金屬量增多,焊核寬度增大。通道過大,軸肩包裹的高溫塑化金屬過多,金屬粘性過低,不利于焊縫金屬的遷移,出現(xiàn)疏松或孔洞缺陷。軸肩結(jié)構(gòu)為側(cè)通道凹槽,可增大焊縫金屬水平運(yùn)動(dòng)的鍛壓力,向下遷移的金屬流截面積增大,焊核尺寸隨之增大。軸肩形貌為外凸時(shí),有利于驅(qū)動(dòng)塑化金屬向攪拌針根部流動(dòng),與螺旋內(nèi)凹結(jié)構(gòu)共同作用,驅(qū)動(dòng)塑化金屬的遷移量最多,焊核寬度最大,洋蔥環(huán)中心高度最低。采用側(cè)通道凹槽軸肩攪拌頭獲得的接頭平均抗拉強(qiáng)度最高,為278.95MPa(達(dá)母材的64.3%);外凸軸肩的接頭抗拉強(qiáng)度最低,為196.04MPa。側(cè)通道凹槽軸肩驅(qū)動(dòng)塑化金屬輻射狀向下遷移,阻止了包鋁層向上伸入;在外凸軸肩的驅(qū)動(dòng)作用下,塑化金屬向焊縫底部遷移時(shí)產(chǎn)生的擠壓力最大,包鋁層向上伸入高度最大,焊核邊界的包鋁層成為接頭受拉伸載荷的起裂和擴(kuò)展區(qū)。
[Abstract]:In this paper, five kinds of shaft-shoulder shafts with concave shape, small channel concave, big channel concave, side channel concave and convex shape are designed. Aluminum foil is used as the marking material. The longitudinal and transverse inlay method was applied to the friction stir welding of aluminum foil and 2A12 aluminum alloy sheet. By observing the shape of the marking material of the three-dimensional section of the weld, the influence of the shaft-shoulder morphology on the plastic flow of the weld metal was studied. The influence law is summarized, and the three-dimensional flow physical model of weld metal under different shaft-shoulder head is established, and the influence of plastic flow on microstructure and properties is analyzed, which provides the practical basis for controlling the formation of friction stir weld. The results show that the force acting on the metal under the shaft shoulder changes, which affects the plastic flow pattern of the weld metal and then changes the shape of the cross section of the weld. The friction between plasticized metal layers can be increased by increasing the pressure of shaft shoulder forging, which is beneficial to the plastic flow of the weld metal, reduces the loose defect and improves the density of the weld. The flow rate of plasticized metal in the action zone of the shaft shoulder can be increased by welding the stirring head of the shaft shoulder with a small channel groove, and the effect of "suction and extrusion" is also enhanced. In unit time, the amount of plasticized metal and the width of nugget are increased from the shaft-shoulder drive to the action zone of the stirring needle and the lower part of the weld. When the channel is too large, too many plasticized metals are wrapped in the shaft shoulder, and the metal viscosity is too low, which is not conducive to the transfer of weld metal, resulting in porosity or hole defects. The shaft-shoulder structure is a side channel groove, which can increase the forging pressure of the horizontal movement of the weld metal, increase the cross section area of the metal flowing down, and increase the size of the welding nugget. When the shape of the shaft shoulder is convex, it is advantageous to drive the plasticizing metal to the root of the agitated needle, and to act together with the spiral concave structure. The mobility of the propelling plasticized metal is the most, the width of the weld core is the largest, and the height of the center of the onion ring is the lowest. The average tensile strength of the joint with side channel groove shaft-shoulder mixing head is the highest, which is 278.95 MPA (64.3% of base metal), and the joint with convex shaft shoulder is the lowest (196.04 MPA). The lateral channel recessed shafts drive the plasticized metal radiate downward to prevent the aluminum cladding from extending upward, while the extruding force of plasticized metal moving to the bottom of the weld is the largest, and the aluminum clad layer reaches the maximum height when the external convex shafts are driven by the shafts. The clad aluminum layer at the nuke boundary becomes the crack initiation and extension zone of the joint under tensile load.
【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】：2015
【分類號(hào)】：TG453.9

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