發(fā)布時間：2018-04-26 01:18

  本文選題：攪拌摩擦焊 + 6061鋁合金��； 參考：《江蘇科技大學(xué)》2017年碩士論文

【摘要】：6061鋁合金是6系鋁合金當中應(yīng)用最多的牌號之一,廣泛應(yīng)用于工業(yè)各領(lǐng)域。攪拌摩擦焊(FSW)作為一種“年輕”的固態(tài)焊接方法為焊接鋁合金提供了一種優(yōu)質(zhì)、高效的新方法。但是,目前學(xué)術(shù)界對FSW焊縫金屬的流動方式、接頭成型機理等仍處在實驗探索階段,尚無權(quán)威定論,因此對其進行研究具有十分重大的意義。本論文對6061-T6和6061-O鋁合金進行了多種對接方式的攪拌摩擦焊接。焊后對各接頭形式的焊縫進行了組織和性能的分析,并通過標記材料示蹤手段研究了異種熱處理狀態(tài)6061鋁合金攪拌摩擦焊接頭的金屬流動性特征。標記材料示蹤法是一種常用的研究材料流動的可視化研究方法,選擇銅粉和銅箔作為標記材料能夠直觀而有效的觀察接頭塑性金屬的遷移方式。拉伸實驗結(jié)果表明,O-O接頭與O-T6接頭屬于塑性斷裂。T6-T6接頭屬于準解理斷裂。T6-T6接頭的顯微硬度曲線呈W形,焊核區(qū)硬度約為母材區(qū)的70%;O-O接頭硬度呈現(xiàn)拋物線形,焊核區(qū)硬度最高,約為母材區(qū)的125%;T6-O接頭與O-T6接頭的顯微硬度曲線雖然總體近似于鏡像對稱關(guān)系,但在局部也存在明顯的區(qū)別。接頭組織方面,焊核區(qū)為細小的等軸晶,晶粒直徑約3-5μm,第二相顆粒分布在晶粒內(nèi)部,第二相主要成分為Mg2Si;熱機影響區(qū)晶粒被拉長,呈長條狀,軸肩影響區(qū)由于動態(tài)再結(jié)晶過程中熱量散失迅速,晶粒最為細小。攪拌針螺紋提供了FSW接頭塑性金屬垂直方向流動的驅(qū)動力,攪拌針的螺紋帶動焊核區(qū)上層金屬向下方遷移,下層金屬不會發(fā)生逆向遷移,只能向更下層遷移。上層金屬無論在垂直還是水平方向上的流動性均更強,遷移距離更遠。在水平方向上,螺紋攪拌針帶動焊核區(qū)塑性金屬旋轉(zhuǎn)運動多個周期,而無螺紋攪拌針僅帶動塑性金屬發(fā)生半個旋轉(zhuǎn)周期的遷移。焊核區(qū)金屬的主要來源是前進側(cè)母材,隨著焊核區(qū)金屬隨攪拌針螺紋向下方遷移,后退側(cè)塑性金屬受到擠壓繞過焊核區(qū)進入焊核區(qū)上方的空腔。前進側(cè)金屬首先進入焊核區(qū),并發(fā)生劇烈的機械攪拌變形,后退側(cè)金屬進入焊核時間較晚,受到的機械作用相對較弱。軸肩影響區(qū)金屬主要來源于后退側(cè),當后退側(cè)金屬為O態(tài)時軸肩影響區(qū)內(nèi)的塑性金屬流動更加劇烈,能夠遷移到更遠的距離,當后退側(cè)金屬為T6態(tài)時軸肩影響區(qū)內(nèi)的塑性金屬流動性較弱。此外,O態(tài)金屬一側(cè)的熱機影響區(qū)寬度更大,T6態(tài)母材一側(cè)的熱機影響區(qū)寬度相對較窄。
[Abstract]:6061 aluminum alloy is one of the most widely used six-series aluminum alloys. It is widely used in various fields of industry. FSW (friction stir Welding), as a "young" solid state welding method, provides a high quality and high efficiency method for aluminum alloy welding. However, the current academic research on the flow mode of FSW weld metal and the forming mechanism of joint is still in the stage of experimental exploration, and there is no authoritative conclusion, so it is of great significance to study the flow mode of FSW weld metal and the mechanism of joint forming. In this paper, friction stir welding of 6061-T6 and 6061-O aluminum alloy is carried out. After welding, the microstructure and properties of the welded joints were analyzed, and the metal fluidity characteristics of friction stir welding joints of 6061 aluminum alloy with dissimilar heat treatment were studied by means of tracer materials. The tracer method is a common visual method to study the flow of materials. Selecting copper powder and copper foil as marking materials can directly and effectively observe the transfer mode of plastic metals in joints. The results of tensile test show that the microhardness curve of the joint between O-O and O-T6 belongs to plastic fracture. T6-T6 joint is quasi-cleavage fracture. The microhardness curve of T6-T6 joint is W shape, and the hardness of 70o joint is parabola, and the hardness of weld nugget zone is the highest. The microhardness curves of 125 T6-O joints and O-T6 joints in the base metal region are similar to mirror symmetry, but there are obvious differences between them. In connection with the microstructure of the joints, the nugget zone is a fine equiaxed crystal, the grain diameter is about 3-5 渭 m, the second phase is distributed inside the grain, the main composition of the second phase is mg _ 2Si, and the grains in the heat engine affected zone are elongated and long. Due to the rapid heat loss in the dynamic recrystallization, the grain size is the smallest in the shaft-shoulder affected zone. The stirring needle thread provides the driving force for the vertical flow of the plastic metal in the FSW joint. The thread of the stirring needle drives the upper layer metal to move downwards in the nuke zone, but the lower layer metal can only migrate to the lower layer instead of the reverse migration. The upper metal is more fluidity in vertical and horizontal direction, and the distance of migration is longer. In the horizontal direction, the screw stirring needle drives the rotation of plastic metal in the nuke zone for several periods, while the non-threaded needle only drives the transfer of the plastic metal for half a rotation cycle. The main source of the metal in the nugget zone is the forward base metal. As the metal in the nugget zone moves down with the stirring needle thread, the plastic metal in the receding side is bypassed into the cavity above the nugget zone by squeezing the nugget zone. The metal on the forward side first enters the nugget zone, and the mechanical stirring deformation occurs, and the metal in the receding side enters the nugget later, so the mechanical action is relatively weak. The metal in the shaft-shoulder affected zone mainly comes from the receding side. When the metal in the receding side is in O state, the plastic metal flow in the shaft-shoulder influence zone is more intense and can migrate to a longer distance. When the metal in the receding side is in the T 6 state, the fluidity of the plastic metal in the axial shoulder affected zone is weak. In addition, the width of the heat engine affected zone on the side of O state metal is larger than that on the side of the base metal of T 6 state, and the width of the heat engine influence zone on the side of T 6 state is relatively narrow.
【學(xué)位授予單位】：江蘇科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG457.14

【參考文獻】

相關(guān)期刊論文 前10條

1 郝云飛;畢煌圣;孫宇明;孫世p，

本文編號：1803837