本文關(guān)鍵詞：Al-23Si-4.5Fe-3Cu-lMg合金轉(zhuǎn)棒誘導(dǎo)形核法半固態(tài)漿料制備及壓鑄成形　出處：《昆明理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 轉(zhuǎn)棒誘導(dǎo)形核法 Al-23Si-4.5Fe-3Cu-1Mg合金 初生Si 富Fe相 流變壓鑄

【摘要】：Fe含量較高的過共晶鋁硅合金中的初生Si、富Fe相等的形貌及分布對合金的性能有非常重要的影響。初生Si、富Fe相在A1-Si合金中作為硬質(zhì)相能提高合金的耐磨性能,但是在鑄造鋁合金中,粗大的初生Si和長針狀的富Fe相會對合金基體產(chǎn)生割裂作用,危害合金的力學(xué)性能。研究證明,半固態(tài)處理能有效地細(xì)化合金中的初生相,改善其形貌,提高合金的力學(xué)性能。本文采用轉(zhuǎn)棒誘導(dǎo)形核法制備AI-23Si-4.5Fe-3Cu-1Mg合金半固態(tài)漿料,研究了不同工藝參數(shù)對合金顯微組織的影響,并分析了半固態(tài)壓鑄條件下合金組織的變化規(guī)律。實驗結(jié)果表明,轉(zhuǎn)棒誘導(dǎo)形核法能有效改善合金顯微組織,不僅能細(xì)化合金中的初生Si、還對合金組織中的富Fe相有明顯的細(xì)化效果,對組織中的共晶相以及其它的物相也有相應(yīng)的影響。不同工藝參數(shù)下,轉(zhuǎn)棒誘導(dǎo)形核法對合金顯微組織的影響表現(xiàn)出不同的規(guī)律。轉(zhuǎn)棒轉(zhuǎn)速變化時,合金熔體的運動狀態(tài)會隨之改變。轉(zhuǎn)速過低時,熔體重力起主要作用,內(nèi)外層熔體在轉(zhuǎn)棒旋轉(zhuǎn)方向的相對速度較小,熔體與轉(zhuǎn)棒的接觸面積較小、厚度較大。轉(zhuǎn)速過高時,轉(zhuǎn)棒產(chǎn)生的離心力起主要作用,熔體在離心力影響下會過早脫離轉(zhuǎn)棒,內(nèi)外層熔體相對速度雖然較大,但熔體在垂直方向上與轉(zhuǎn)棒的接觸面積減小,使得在高轉(zhuǎn)速時熔體與轉(zhuǎn)棒的接觸面積減小。導(dǎo)熱系數(shù)高的銅質(zhì)轉(zhuǎn)棒能在同時間內(nèi)帶走熔體更多的熱量,其形核效果優(yōu)于鋼質(zhì)轉(zhuǎn)棒。澆注溫度過高時漿料內(nèi)殘存熱量較多,降低半固態(tài)漿料中游離晶核的密度,并產(chǎn)生成分過冷,促進(jìn)晶粒生長。澆注溫度過高時,熔體中已形成的晶粒會發(fā)生重熔的現(xiàn)象,降低熔體中游離晶核密度,最終長大成大尺寸晶粒。研究結(jié)果表明,采用φ75mm銅質(zhì)轉(zhuǎn)棒,轉(zhuǎn)棒轉(zhuǎn)速為600r/min,澆注溫度為830℃時,合金的細(xì)化效果最佳,初生Si、富Fe相分別細(xì)化至32μm、34μm。采用壓鑄工藝制備了液態(tài)常規(guī)壓鑄件和半固態(tài)壓鑄件,分析了壓鑄件中的組織變化規(guī)律,發(fā)現(xiàn)壓鑄工藝不僅能細(xì)化合金組織中的初生Si、富Fe相等初生相,還對富Cu相、共晶組織的形態(tài)和分布有著明顯的優(yōu)化作用。在半固態(tài)壓鑄成形制備的壓鑄件中,初生Si和富Fe相的尺寸分別減小至15μm、20μm,并且,隨壓射流程的增加,顯微組織中二次初生相的體積分?jǐn)?shù)明顯增加。
[Abstract]:The primary Si in hypereutectic Al-Si alloy with high Fe content has a very important effect on the properties of hypereutectic Al-Si alloy. Fe-rich phase as a hard phase in A _ 1-Si alloy can improve the wear resistance of the alloy, but in casting aluminum alloy, the coarse primary Si and the long needle-rich Fe phase will split the alloy matrix. It is proved that semi-solid treatment can refine the primary phase and improve the morphology of the alloy effectively. In order to improve the mechanical properties of AI-23Si-4.5Fe-3Cu-1Mg alloy, semi-solid slurry of AI-23Si-4.5Fe-3Cu-1Mg alloy was prepared by rod-induced nucleation method. The effect of different process parameters on the microstructure of the alloy was studied, and the changes of the microstructure of the alloy under the condition of semi-solid die-casting were analyzed. The experimental results show that the rod-induced nucleation method can effectively improve the microstructure of the alloy. Not only the primary Si in the alloy can be refined, but also the Fe-rich phase in the alloy structure can be refined obviously, and the eutectic phase and other phases in the microstructure can also be affected accordingly. The effect of rod-induced nucleation on the microstructure of the alloy is different. When the rotating speed of the alloy changes, the moving state of the melt will change. When the rotational speed is too low, the gravity of the melt plays a major role. The relative velocity of inner and outer layer melt in rotating direction is smaller, the contact area between melt and rotating rod is smaller, the thickness is larger, and the centrifugal force produced by rotating rod plays a major role when the rotational speed is too high. Under the influence of centrifugal force, melt will get rid of the rotating rod prematurely. Although the relative velocity of melt inside and outside layer is larger, the contact area between melt and rotating rod in the vertical direction decreases. The contact area between melt and rotor decreases at high rotational speed, and the copper rod with high thermal conductivity can take more heat away from the melt at the same time. The nucleation effect is better than that of steel bars. When the pouring temperature is too high, the residual heat in the slurry is more, the density of free crystal nucleus in semi-solid slurry is reduced, and the composition is supercooled to promote the grain growth. The grain formed in the melt will remelt, reduce the density of free nucleus in the melt, and eventually grow into large grain. The results show that the 蠁 75mm copper bar is used. When the rotating speed of the alloy is 600 r / min and the pouring temperature is 830 鈩，

本文編號：1429599