本文關(guān)鍵詞： 噴射成形鋁合金 攪拌摩擦焊 顯微組織 力學(xué)性能 初始狀態(tài)　出處：《江蘇科技大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：噴射成形技術(shù)制備的鋁合金組織均勻細(xì)小,無明顯宏觀偏析,采用傳統(tǒng)熔化焊焊接噴射成形鋁合金時(shí)接頭軟化現(xiàn)象嚴(yán)重,大大降低材料性能。攪拌摩擦焊作為一種固態(tài)焊接方法能有效焊接噴射成形鋁合金。對(duì)T76態(tài)噴射成形7055進(jìn)行焊接并測(cè)溫,研究焊接工藝參數(shù)對(duì)熱循環(huán)和組織性能的影響。通過拉伸和硬度試驗(yàn)分析工藝參數(shù)對(duì)接頭力學(xué)性能的影響,采用OM、SEM等手段對(duì)接頭進(jìn)行微觀分析,研究工藝參數(shù)、組織和性能之間的關(guān)系。然后對(duì)擠壓態(tài)、固溶態(tài)噴射成形7055進(jìn)行焊接并對(duì)擠壓態(tài)和固溶態(tài)接頭進(jìn)行后續(xù)熱處理,研究母材初始狀態(tài)和焊后熱處理對(duì)接頭組織和性能的影響。測(cè)溫結(jié)果表明,攪拌摩擦焊接過程中各點(diǎn)溫度先升高再降低。焊縫初始、穩(wěn)定、結(jié)束階段所達(dá)到的溫度峰值逐漸上升。各點(diǎn)溫度峰值隨著旋轉(zhuǎn)速度的提高和焊接速度的降低而上升。后退側(cè)溫度低于前進(jìn)側(cè)溫度。距離焊縫上表面越遠(yuǎn)溫度越低。接頭宏觀上可以看出,飛邊主要出現(xiàn)在后退側(cè),下壓量固定的情況下焊接速度減小或旋轉(zhuǎn)速度提高,飛邊更加嚴(yán)重。焊核中心區(qū)寬度隨著焊接速度的減小或旋轉(zhuǎn)速度的提高而變寬。微觀分析表明,隨著焊接速度的減小和旋轉(zhuǎn)速度的提高,焊核區(qū)和部分熱機(jī)械影響區(qū)發(fā)生再結(jié)晶,力學(xué)性能優(yōu)良,熱影響區(qū)晶粒長(zhǎng)大成為接頭薄弱區(qū)域。焊核區(qū)上部析出相數(shù)量少、尺寸大,焊核中下部析出相數(shù)量多尺寸較小,焊核中下部出現(xiàn)孔洞。熱機(jī)械影響區(qū)析出相的數(shù)量和尺寸與焊核區(qū)中下部大體相同但表現(xiàn)出了明顯的方向性。熱影響區(qū)第二相部分溶解,白色顆粒數(shù)量少。當(dāng)旋轉(zhuǎn)速度較小時(shí),析出相數(shù)量較少尺寸較小。隨著焊接速度的減小,焊核區(qū)域析出相出現(xiàn)長(zhǎng)大。隨著焊接速度和旋轉(zhuǎn)速度的提高,接頭抗拉強(qiáng)度和延伸率先降低再提高。轉(zhuǎn)速為1350rpm焊速為75mm/min時(shí),抗拉強(qiáng)度467.12MPa,達(dá)到母材強(qiáng)度的86.0%。隨著旋轉(zhuǎn)速度的提高,熱影響區(qū)寬度變大,熱影響區(qū)最低硬度值變小。不同焊接速度下熱影響區(qū)寬度變化不大,大約都為3mm,但是熱影響區(qū)最低硬度值先降低再提高。旋轉(zhuǎn)速度1350rpm,焊速75mm/min時(shí),擠壓態(tài)、固溶態(tài)母材攪拌摩擦焊接均能得到無明顯宏觀缺陷的接頭,并且接頭再進(jìn)行熱處理也不出現(xiàn)宏觀缺陷。擠壓態(tài)焊接完后進(jìn)行T76處理的接頭隨焊核區(qū)晶粒發(fā)生異常長(zhǎng)大但抗拉強(qiáng)度為496.1MPa,達(dá)到母材強(qiáng)度的91.4%,接頭顯微硬度與母材相當(dāng),約195HV。
[Abstract]:The microstructure of aluminum alloy prepared by spray forming technology is uniform and fine, and there is no obvious macro segregation. The softening phenomenon of joint is serious when conventional melting welding is used to weld spray formed aluminum alloy. Friction stir welding (FSW) as a solid-state welding method can effectively weld spray formed aluminum alloy. T76 state spray forming 7055 is welded and temperature measured. The effects of welding parameters on thermal cycling and microstructure and properties were studied. The effects of process parameters on mechanical properties of joints were analyzed by tensile and hardness tests. The relationship among process parameters, microstructure and properties was studied. Then the extrusion, solid solution spray forming 7055 was welded and the extruded and solid solution joints were treated by subsequent heat treatment. The effect of initial state of base metal and heat treatment after welding on the microstructure and properties of joints was studied. The results of temperature measurement showed that the temperature of each point in friction stir welding first increased and then decreased. The temperature peak at the end stage gradually increased. The peak temperature of each point increased with the increase of rotation speed and the decrease of welding speed. The temperature of the receding side was lower than that of the forward side. The farther the temperature was from the upper surface of the weld, the lower the temperature was. The joint can be seen macroscopically. The flange mainly appears in the receding side, and the welding speed decreases or the rotation speed increases when the pressure is fixed. The width of the center zone of the nugget becomes wider with the decrease of the welding speed or the increase of the rotating speed. The microcosmic analysis shows that the width of the center area of the welding nugget increases with the decrease of the welding speed and the increase of the rotation speed. Recrystallization occurs in the nugget zone and part of the thermomechanical zone, and the mechanical properties are good. The grain growth in the HAZ becomes the weak zone of the joint, and the upper part of the nugget zone has a small number of precipitated phases and a large size. The number of precipitated phases in the middle and lower part of the nugget is much smaller. The number and size of precipitated phases in the HAZ are approximately the same as those in the middle and lower parts of the nugget zone but show obvious directionality. The second phase in the HAZ is dissolved. The number of white particles is small. When the rotation speed is small, the number of precipitates is smaller. With the decrease of welding speed, the precipitates in the nugget region grow up, and with the increase of welding speed and rotation speed. The tensile strength and extension of the joint decreased and then increased first. The tensile strength of the joint was 467.12MPa when the welding speed was 75mm / min at 1350rpm. With the increase of rotation speed, the width of HAZ becomes larger, and the minimum hardness value of HAZ becomes smaller. The width of HAZ varies little with different welding speed, all of them are about 3 mm. However, the minimum hardness of the HAZ decreases first and then increases. When the rotation speed is 1350rpm, the welding speed is 75mm / min, the extrusion state is obtained. The joints without macroscopic defects can be obtained by solid solution base metal friction stir welding. The joints treated with T76 after welding in extruded state have abnormal growth but tensile strength is 496.1 MPA. To reach 91.4 of the base metal strength, the microhardness of the joint is about the same as the base metal, about 195HV.
【學(xué)位授予單位】：江蘇科技大學(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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