發(fā)布時(shí)間：2019-05-11 00:36

【摘要】：鋁合金是輕量化首選的金屬材料,發(fā)展高強(qiáng)韌性鋁合金是擴(kuò)大其在結(jié)構(gòu)材料上應(yīng)用的關(guān)鍵,形變熱處理工藝對鋁合金的力學(xué)性能有很大影響。本工作對固溶態(tài)、預(yù)時(shí)效態(tài)和T6態(tài)6016鋁合金的低溫形變熱處理行為進(jìn)行了深入研究,三種狀態(tài)的鋁合金經(jīng)過低溫下軋制以及后續(xù)低溫時(shí)效后,力學(xué)性能和組織的變化各不相同。固溶態(tài)鋁合金低溫軋制后屈服強(qiáng)度是軋制前的6.5倍,但是伸長率嚴(yán)重下降,再經(jīng)過低溫時(shí)效后,伸長率得到顯著改善。觀察微觀結(jié)構(gòu)特征發(fā)現(xiàn),低溫軋制能抑制動(dòng)態(tài)回復(fù),形成高密度的位錯(cuò)和變形亞結(jié)構(gòu),并細(xì)化晶粒組織,對合金有很大的強(qiáng)化作用。低溫時(shí)效時(shí),同時(shí)發(fā)生強(qiáng)化相析出和回復(fù)或部分再結(jié)晶作用,使時(shí)效后的鋁合金在拉伸時(shí)有更高的的加工硬化率,這是改善延展性的關(guān)鍵。預(yù)時(shí)效態(tài)鋁合金低溫軋制后獲得更高的強(qiáng)度,但是伸長率也更低,再經(jīng)過低溫時(shí)效后,可使強(qiáng)度和伸長率都進(jìn)一步提高。軋制后強(qiáng)度的提高是由于時(shí)效強(qiáng)化、位錯(cuò)和晶界強(qiáng)化共同作用的結(jié)果。預(yù)時(shí)效能加快低溫時(shí)效時(shí)強(qiáng)化相的析出速度,對力學(xué)性能的提高有重要作用。T6態(tài)鋁合金低溫軋制后擁有最高的強(qiáng)度,但是伸長率最低,高的強(qiáng)度主要來自時(shí)效強(qiáng)化作用。再經(jīng)過低溫時(shí)效后強(qiáng)度減小,伸長率也沒有明顯改善,分析微觀組織演變特征發(fā)現(xiàn),低溫時(shí)效時(shí)形成強(qiáng)化效果更低的析出相,鋁合金的加工硬化能力也下降。論文還討論了不同的強(qiáng)化機(jī)理對三種狀態(tài)的鋁合金在低溫形變熱處理過程中強(qiáng)度的貢獻(xiàn)。結(jié)果得出,隨著低溫軋制前鋁合金時(shí)效程度的增加,低溫形變熱處理過程中時(shí)效強(qiáng)化作用逐漸提高,位錯(cuò)和晶界強(qiáng)化作用逐漸下降。
[Abstract]:Aluminum alloy is the preferred metal material. The development of high strength and toughness aluminum alloy is the key to expand its application in structural materials. The deformation heat treatment process has a great influence on the mechanical properties of aluminum alloy. In this work, the mechanical properties and microstructure of 6016 aluminum alloys in solid solution state, pre-aging state and T6 state were studied. The mechanical properties and microstructure of the three states aluminum alloys were different after rolling at low temperature and subsequent low-temperature aging. The mechanical properties and microstructure of aluminum alloys in three states were different after low-temperature rolling and subsequent low-temperature aging. The yield strength of solid solution aluminum alloy after low temperature rolling is 6.5 times higher than that before rolling, but the extension rate decreases seriously, and then after low temperature aging, the yield strength is significantly improved. It is found that low temperature rolling can inhibit dynamic recovery, form high density dislocation and deformation substructure, and refine grain structure, which has great strengthening effect on the alloy. At low temperature aging, the precipitation and recovery of strengthening phase or partial crystallization occur at the same time, which makes the aged aluminum alloy have a higher processing hardening rate during drawing, which is the key to improve the extensibility. After low temperature rolling, the strength of preaging aluminum alloy is higher, but the elongation is also lower. After low temperature aging, the strength and extension of aluminum alloy can be further improved. The increase of strength after rolling is due to the joint action of aging strengthening, dislocation and grain boundary strengthening. It is important to improve the mechanical properties of T6 aluminum alloy by accelerating the precipitation rate of the strengthening phase during low temperature aging. After low temperature rolling, T6 aluminum alloy has the highest strength, but the lowest elongation, and the high strength is mainly due to the aging strengthening effect. After low temperature aging, the strength decreased and the elongation did not improve obviously. It was found that the precipitation phase with lower strengthening effect was formed at low temperature aging, and the working hardening ability of aluminum alloy also decreased. The contribution of different strengthening mechanisms to the strength of three states of aluminum alloy during low temperature deformation heat treatment is also discussed in this paper. The results show that with the increase of aging degree of aluminum alloy before low temperature rolling, the aging strengthening effect increases gradually, while the dislocation and grain boundary strengthening effect decreases gradually during low temperature deformation heat treatment.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG146.21;TG166.3

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