本文選題：微束等離子弧堆焊　切入點(diǎn)：TC4鈦合金　出處：《中國(guó)民航大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：本文研究了焊接工藝參數(shù)對(duì)不同板厚TC4鈦合金微束等離子弧堆焊接頭成型的影響規(guī)律,結(jié)果表明焊接電流和送絲速度對(duì)接頭成型影響較大,對(duì)不同板厚的影響規(guī)律相同;槍距對(duì)接頭成型影響較小,對(duì)不同板厚的影響規(guī)律存在較大差異,對(duì)于窄板,隨槍距的增大,堆焊層高度增大寬度減小;對(duì)于寬板,隨槍距增大,堆焊層高度減小寬度增大。在本實(shí)驗(yàn)焊接工藝下,焊縫外部為單向生長(zhǎng)α′相馬氏體長(zhǎng)針,而焊縫內(nèi)部為網(wǎng)籃組織。熱影響區(qū)主要由α′相、初生α相和β相組成,熱影響區(qū)組織分布具有差異性,靠近母材區(qū)域晶粒相對(duì)細(xì)小且α′相針狀馬氏體含量少。焊縫內(nèi)部還會(huì)出現(xiàn)團(tuán)束組織和塊狀α相等特殊組織。隨著焊接電流的增大,焊縫外部的馬氏體長(zhǎng)針逐漸粗大,內(nèi)部針狀α′相馬氏體逐漸呈多向雜亂分布,同時(shí)焊縫內(nèi)部β柱狀晶尺寸變大;增大送絲速度,焊縫內(nèi)部馬氏體長(zhǎng)針數(shù)量減少,β柱狀晶減少;槍距對(duì)于焊縫內(nèi)部組織的變化影響較小。焊接工藝參數(shù)對(duì)焊縫內(nèi)部相組成變化影響較小,焊縫內(nèi)部均為大量α′相和少量β相。焊接試樣顯微硬度值由焊縫-熱影響區(qū)-母材依次降低,焊接工藝對(duì)接頭硬度值影響較小。焊接接頭抗拉強(qiáng)度高于或等于母材,焊縫區(qū)脆性較大,塑性比母材差,但強(qiáng)度高于母材。焊縫區(qū)的斷裂韌性相比于母材較差。去應(yīng)力熱處理工藝對(duì)焊接接頭的組織和相組成影響較小;對(duì)接頭硬度有一定的改善作用,降低了部分區(qū)域過高的硬度值;經(jīng)過熱處理的試件拉伸斷口位置與未經(jīng)熱處理的試件存在差別,未經(jīng)熱處理的試件斷裂位置距離焊縫較近;熱處理對(duì)試件的斷裂韌性影響不明顯。
[Abstract]:In this paper, the influence of welding process parameters on the forming of TC4 titanium alloy surfacing joints with different plate thickness is studied. The results show that the welding current and wire feeding speed have great influence on the joint forming, and the effects on different plate thickness are the same. The influence of gun distance on joint forming is small, and the influence law of different plate thickness is different. For narrow plate, the width of surfacing layer height decreases with the increase of gun distance, while for wide plate, it increases with gun distance. The height of the surfacing layer decreases and the width increases. In this experimental welding process, the outside of the weld is a long pin of 偽 'phase martensite, while the inner part of the weld is a basket structure. The heat affected zone is mainly composed of 偽' phase, primary 偽 phase and 尾 phase, and the heat affected zone is mainly composed of 偽 'phase, primary 偽 phase and 尾 phase. The microstructure distribution of the heat-affected zone is different, the grain is relatively small near the base metal and the content of 偽 '-phase acicular martensite is less. There will also be a special structure of cluster structure and block 偽 inside the weld seam. With the increase of welding current, The martensite long needle outside the weld gradually became coarse, and the internal 偽 '-phase martensite gradually distributed in a multi-direction disorder, and the size of 尾 columnar crystal in the weld increased, and the number of martensite long needles decreased and the 尾 columnar crystal decreased with the increase of wire feeding speed. The influence of the gun distance on the internal structure of the weld is small, and the welding process parameters have little effect on the change of the internal phase composition of the weld. The microhardness of welding specimens decreased from weld to heat affected zone to base metal in turn, and the welding process had little effect on the hardness of joint. The tensile strength of welded joint was higher than or equal to that of base metal. The weld zone is brittleness, the plasticity is worse than the base metal, but the strength is higher than the base metal. The fracture toughness of the weld zone is worse than that of the base metal. The effect of stress free heat treatment on the microstructure and phase composition of the welded joint is less. It can improve the hardness of the joint and decrease the hardness value of some regions, the tensile fracture position of the heat-treated specimen is different from that of the non-heat-treated specimen, and the fracture position of the unheat-treated specimen is closer to the weld seam. The effect of heat treatment on fracture toughness is not obvious.
【學(xué)位授予單位】：中國(guó)民航大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG457.1

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