本文選題：異種鋁合金　切入點(diǎn)：數(shù)值模擬　出處：《西南石油大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：2A12鋁合金和7075鋁合金是可熱處理高強(qiáng)鋁合金,鋁合金的材料密度低,比強(qiáng)度較高。這類材料逐漸成為現(xiàn)代高速列車(chē)、轎車(chē)與小型汽車(chē)的理想替代材料。激光-MIG復(fù)合焊集合了激光焊和MIG焊兩種熱源的優(yōu)勢(shì),用于鋁合金焊接時(shí),不僅焊接效率高,缺陷少,而且還可以改善焊接接頭的組織與性能。本文首先通過(guò)數(shù)值模擬,得到焊接接頭溫度場(chǎng)、焊板總變形量、焊縫背寬、熔寬以及焊接接頭跟蹤點(diǎn)溫度、變形量的變化規(guī)律,然后以焊板總變形量為主要依據(jù),選擇出合適的工藝參數(shù)進(jìn)行實(shí)際焊接,并通過(guò)實(shí)驗(yàn)數(shù)據(jù)對(duì)數(shù)值模擬的焊縫背寬、熔寬和焊接接頭總變形量進(jìn)行對(duì)比驗(yàn)證;接下來(lái)分析激光功率、焊接電流對(duì)焊接接頭成形性以及焊接接頭顯微組織的影響,結(jié)合EDS和XRD,探究焊接接頭中物相的組成;還分析了激光功率、焊接電流對(duì)焊接接頭顯微硬度、抗拉強(qiáng)度、延伸率、沖擊韌性等力學(xué)性能的影響,并對(duì)拉伸斷口進(jìn)行分析。選擇綜合性能較好的焊接接頭進(jìn)行180℃12h的時(shí)效處理,分析時(shí)效對(duì)焊接接頭顯微硬度、抗拉強(qiáng)度的影響。具體研究結(jié)論如下:數(shù)值模擬研究表明:激光功率為3.8 KW、焊接電流為195 A時(shí),數(shù)值模擬與實(shí)際焊接在焊縫熔寬、背寬方面,對(duì)比驗(yàn)證比較符合。在焊接總變形量方面,2A12鋁合金側(cè)驗(yàn)證結(jié)果比7075鋁合金側(cè)好。整體來(lái)說(shuō),數(shù)值模擬對(duì)實(shí)際焊接有比較大的指導(dǎo)價(jià)值。焊接接頭成形性研究表明:復(fù)合焊焊縫的全透性和鋪展性隨著激光功率的增加而增加,且焊縫的激光作用區(qū)直徑和背寬增加,焊縫熔寬變化不大;焊接電流的增加,可以提高復(fù)合焊焊縫的全透性,但是其鋪展性有所降低;激光焊焊縫熔深隨激光功率增加而增加,但焊縫金屬元素的燒損加劇。焊接接頭顯微組織研究表明:2A12鋁合金側(cè)熱影響區(qū)晶粒發(fā)生了明顯的粗化,固溶區(qū)尤為嚴(yán)重;7075鋁合金側(cè)晶粒比2A12鋁合金側(cè)粗大;隨著激光功率和焊接電流的增加,固溶區(qū)強(qiáng)化相數(shù)量減少,焊縫上部2A12鋁合金側(cè)柱狀晶減少,7075鋁合金側(cè)的柱狀晶減少的更加明顯,但是焊縫的晶粒卻發(fā)生了粗化;激光焊接頭熔合線附近焊縫的晶粒是典型的柱狀晶,焊縫上部的柱狀晶更明顯。焊接接頭力學(xué)性能研究表明:接頭兩側(cè)顯微硬度最低位置隨著激光功率和焊接電流的增加,距離焊縫中心越遠(yuǎn);激光功率對(duì)接頭抗拉強(qiáng)度和延伸率影響不大;而焊接電流的增加,使得接頭的抗拉強(qiáng)度有所下降,延伸率有所增長(zhǎng),斷裂位置遠(yuǎn)離焊縫;激光功率對(duì)接頭沖擊韌性影響并不是很明顯;增加焊接電流,接頭沖擊韌性下降。時(shí)效處理可以提高接頭的綜合力學(xué)性能。綜上可知,激光-MIG復(fù)合焊方法更適合異種鋁合金的焊接。激光-MIG復(fù)合焊的最佳工藝參數(shù)為激光功率3.8 KW,焊接電流195 A。
[Abstract]:2A12 aluminum alloy and 7075 aluminum alloy are heat-treated high-strength aluminum alloys with low density and high specific strength. Laser MIG hybrid welding combines the advantages of laser welding and MIG welding. When used in aluminum alloy welding, it not only has high welding efficiency, but also has less defects. It can also improve the microstructure and properties of welded joints. Firstly, through numerical simulation, the temperature field of welded joints, total deformation of welded plates, weld back width, weld width, temperature and deformation of welding joint tracking point are obtained. Then based on the total deformation of the welding plate, the suitable process parameters are selected for actual welding, and the numerical simulation of weld back width, weld width and total deformation of welded joint are compared and verified by experimental data. Then, the effects of laser power, welding current on the formability and microstructure of welded joints are analyzed, and the phase composition in welded joints is explored by combining EDS and XRD.The microhardness of welded joints is also analyzed by laser power and welding current. The effects of tensile strength, elongation, impact toughness and other mechanical properties on tensile fracture were analyzed. The welding joints with better comprehensive properties were selected for aging treatment at 180 鈩，

本文編號(hào)：1621114