發(fā)布時(shí)間：2018-10-18 20:09

【摘要】：Al-Zn-Mg-Cu(7xxx系列)系鋁合金由于具有低密度、高強(qiáng)度、高塑性等優(yōu)點(diǎn),廣泛應(yīng)用于軌道交通和航空航天領(lǐng)域,但該類合金常規(guī)鑄造時(shí)容易產(chǎn)生熱裂等缺陷,使其難以通過(guò)常規(guī)鑄造方式直接生產(chǎn)高性能零件。本文系統(tǒng)地研究了 7A04鋁合金流變成形中的半固態(tài)漿料制備、壓鑄成形及鑄件熱處理,以期為實(shí)現(xiàn)7A04鋁合金流變成形工業(yè)生產(chǎn)奠定基礎(chǔ)。本文通過(guò)對(duì)添加Al-5Ti-1B細(xì)化劑制備的7A04鋁合金半固態(tài)漿料組織的分析,系統(tǒng)的研究了 Al-5Ti-1B細(xì)化劑添加量對(duì)初生α-Al顆粒及后續(xù)二次凝固產(chǎn)生的α2和α3顆粒的平均尺寸和圓整度的影響規(guī)律,同時(shí)研究了 Al-5Ti-1B細(xì)化劑對(duì)鋁合金半固態(tài)漿料組織徑向均勻性的影響。結(jié)果表明:添加Al-5Ti-1B細(xì)化劑可以明顯改善7A04鋁合金半固態(tài)漿料初生α-Al顆粒和α2顆粒,但對(duì)α3顆粒尺寸和圓整度及7A04鋁合金物相無(wú)顯著影響。在漿料溫度630℃下,添加0.1%的Al-5Ti-1B細(xì)化劑制備的7A04鋁合金半固態(tài)漿料的初生α-Al顆粒和α2顆粒的平均直徑和圓整度分別為71μm和0.49、29μm和0.45。當(dāng)Al-5Ti-1B細(xì)化劑的添加量超過(guò)0.1%,隨著細(xì)化劑添加量的增加,細(xì)化效果無(wú)明顯提高。添加Al-5Ti-1B細(xì)化劑可以改善7A04鋁合金半固態(tài)漿料組織在徑向上的均勻性,在635℃下,變異系數(shù)Cv為2.8%。本文通過(guò)對(duì)添加不同量的Al-5Ti-1B細(xì)化劑的7A04鋁合金熔體進(jìn)行壓鑄,系統(tǒng)的研究了在壓鑄溫度、細(xì)化劑添加量和壓射速度對(duì)鑄件的初生α-Al顆粒及二次凝固組織、鑄件內(nèi)部的孔隙率及力學(xué)性能的影響。結(jié)果表明:添加A1-5Ti-1B可以細(xì)化圓整鑄件的初生α-Al顆粒,細(xì)化圓整效果在壓鑄溫度635℃時(shí)最明顯;隨著Al-5Ti-1B添加量的增多,細(xì)化效果無(wú)明顯提高;Al-5Ti-1B添加量對(duì)鑄件的孔隙率及力學(xué)性能的影響不明顯。壓鑄溫度分別為720℃和660℃時(shí),鑄件的顆粒尺寸隨壓射速度的增大無(wú)明顯變化,圓整度略有提高;壓鑄溫度為635℃時(shí),7A04鋁合金鑄件的初生α-Al顆粒尺寸隨壓射速度的增大而減小,圓整度明顯提高。鑄件的二次凝固組織中α2顆粒平均尺寸和圓整度隨壓射速度的增大無(wú)明顯變化。壓鑄溫度相同,7A04鋁合金壓鑄件的孔隙率、密度及抗拉強(qiáng)度和延伸率都是在速度控制閥第四圈時(shí)最優(yōu);壓射速度相同時(shí),鑄件的孔隙率隨壓鑄溫度的降低而減小,而密度及力學(xué)性能增大。本文通過(guò)對(duì)添加Al-5Ti-1B細(xì)化劑的7A04鋁合金壓鑄件進(jìn)行熱處理,研究了在不同壓鑄溫度下、不同Al-5Ti-1B添加量下熱處理對(duì)該合金壓鑄件內(nèi)部的孔隙率及力學(xué)性能的影響。結(jié)果表明:Al-5Ti-1B添加量的增加對(duì)熱處理后的鑄件的孔隙率及力學(xué)性能無(wú)明顯影響。熱處理后的鑄件與未熱處理相比,孔隙率略微增加,密度略微減小,但抗拉強(qiáng)度和延伸率明顯提高,最大值分別為391MPa和2.5%,但由于孔洞的存在,鑄件的力學(xué)性能與鍛件相比還有很大的差距。
[Abstract]:Al-Zn-Mg-Cu (7xxx series) aluminum alloys are widely used in rail transit and aerospace fields because of their advantages of low density, high strength and high plasticity. It is difficult to produce high performance parts directly by conventional casting. In this paper, the preparation of semi-solid slurry, die casting and heat treatment of 7A04 aluminum alloy rheological forming are studied systematically, in order to lay a foundation for the industrial production of 7A04 aluminum alloy rheological forming. In this paper, the microstructure of semi-solid slurry of 7A04 aluminum alloy prepared by adding Al-5Ti-1B refiner was analyzed. The effects of the addition of Al-5Ti-1B refiner on the average size and roundness of primary 偽 Al particles and 偽 2 and 偽 3 particles produced by subsequent secondary solidification were studied systematically. At the same time, the effect of Al-5Ti-1B refiner on the radial uniformity of aluminum alloy semi-solid slurry was studied. The results show that the addition of Al-5Ti-1B refiner can obviously improve the primary 偽-Al and 偽 2 particles of 7A04 aluminum alloy semi-solid slurry, but has no significant effect on the size and roundness of 偽 3 particles and the phase of 7A04 aluminum alloy. At 630 鈩，

本文編號(hào)：2280234