發(fā)布時間：2019-01-23 20:41

【摘要】：本文采用兩種方法提高初晶硅異質形核效率,實現(xiàn)高硅Al-Si合金有效細化。一種是制備高含磷量的Si-Ti-P系中間合金,分析中間合金的相組成及其在Al-Si熔體中的演變過程,并以此為依據(jù)設計Si-Ti-P系中間合金的使用參數(shù)。對比Cu-14P、Al-3P、Si-Ti-P系中間合金對Al-27Si合金的細化效果,并討論磷細化處理對Al-27Si合金的熱膨脹系數(shù)和拉伸性能的影響。另一種是改進細化工藝,同時引入AlP和TiB_2粒子,驗證TiB_2@AlP復合粒子對Al-45Si合金的細化效果,并提出吸附形成機制。本文主要研究工作如下:(1)Si-Ti-P系中間合金在Al-Si熔體中的演變行為分析了 Si基合金中磷化物的存在形式。研究發(fā)現(xiàn),通過向Si-Mn-P合金中引入過渡族金屬元素Ti、Fe、Cu,可促使原Si-Mn-P合金中的磷化合物發(fā)生轉變。在Si-P系合金中,過渡族金屬元素的"固磷"效果不同。Si-Ti-P系中間合金中,磷化物主要為TiP相。在Al-Si熔體環(huán)境下,中間合金中的TiP相與Al-Si熔體發(fā)生反應,產物為AlP和(Al,Si,Ti)三元化合物。研究發(fā)現(xiàn),TiP相與Al-Si熔體間會發(fā)生化學勢差驅動的液-固擴散反應。將Si-Ti-P系中間合金加入到Al-Si熔體后,硅基體首先熔解,使TiP相與鋁熔體接觸。在化學勢差驅動下,TiP演變?yōu)锳lP,此演變的反應速率受擴散控制。因此使用Si-Ti-P系中間合金細化處理Al-Si熔體時,需要一定的保溫時間來獲得較好的細化效果。提高反應溫度,增加熔體對流等可加快TiP相向AlP相演變,縮短保溫時間。(2)Si-Ti-P系中間合金對過共晶Al-Si合金的細化行為與Cu-14P和Al-3P相比,使用Si-Ti-P系中間合金細化后的Al-27Si合金中初晶硅尺寸更細小,形狀更規(guī)整,分布更均勻。通過Si-Ti-P系中間合金向Al-27Si熔體中加入350ppm磷,在850℃保溫_20分鐘,初晶硅尺寸可細化至 14.7±1.3μm。對磷細化前后的Al-27Si合金進行熱膨脹系數(shù)和拉伸性能進行測試,發(fā)現(xiàn)磷細化處理有助于降低Al-27Si合金的熱膨脹系數(shù)并提高合金的拉伸性能。使用Si-Ti-P系中間合金細化處理Al-27Si合金后,合金的熱膨脹系數(shù)降至16.25×10-6/K。與未細化的合金相比,極限拉伸強度和延伸率分別提高106%和235%。(3)AIP復合粒子對高硅Al-Si合金的細化行為完善了TiB_2@AlP形成機制,驗證了TiB_2@AlP粒子對Al-45Si合金中初晶硅的細化效果。在Al-Si熔體中,P原子傾向于吸附在TiB_2表面形成富磷的吸附層,在過冷度的驅動下富磷吸附層轉變?yōu)锳lP,形成復合的TiB_2@AlP粒子。密度泛函理論計算顯示,P原子更易于被吸附在以Ti終止的(0001)TiB_2界面上,并且傾向于靠近Ti原子。與單獨引入AlP相比,引入TiB_2@AlP粒子對Al-45Si合金有更好的細化效果。在1300℃保溫5分鐘后,初晶硅尺寸可細化至30.1±1.9μm。
[Abstract]:In this paper, two methods are used to improve the efficiency of heterogeneous nucleation of primary silicon and to realize effective refinement of high silicon Al-Si alloy. One is to prepare Si-Ti-P master alloy with high phosphorus content. The phase composition of master alloy and its evolution in Al-Si melt are analyzed, and the application parameters of Si-Ti-P master alloy are designed. The refining effect of Cu-14P,Al-3P,Si-Ti-P master alloy on Al-27Si alloy was compared, and the effect of phosphorus refining treatment on thermal expansion coefficient and tensile properties of Al-27Si alloy was discussed. The other one is to improve the refining process and introduce AlP and TiB_2 particles to verify the refining effect of TiB_2@AlP composite particles on Al-45Si alloy and propose the mechanism of adsorption formation. The main work of this paper is as follows: (1) the evolution behavior of Si-Ti-P master alloys in Al-Si melts has been studied. The existing forms of phosphates in Si based alloys have been analyzed. It is found that the transition group metal element Ti,Fe,Cu, can promote the transformation of phosphorus compounds in the Si-Mn-P alloy. In the Si-P alloy, the effect of the transition group metal element is different. In the Si-Ti-P master alloy, the phosphates are mainly TiP phase. In the Al-Si melt environment, the TiP phase in the master alloy reacts with the Al-Si melt and the product is AlP and (Al,Si,Ti) ternary compound. It is found that the liquid-solid diffusion reaction driven by chemical potential difference will occur between the TiP phase and the Al-Si melt. After the Si-Ti-P master alloy was added to the Al-Si melt, the silicon matrix was first melted to make the TiP phase contact with the aluminum melt. The reaction rate of TiP to AlP, is controlled by diffusion driven by chemical potential difference. Therefore, when the Si-Ti-P master alloy is used to refine the Al-Si melt, a certain holding time is needed to obtain a better refining effect. Increasing reaction temperature and melt convection can accelerate the evolution of TiP phase to AlP phase and shorten the holding time. (2) the refinement behavior of Si-Ti-P master alloy to hypereutectic Al-Si alloy is compared with that of Cu-14P and Al-3P. The size, shape and distribution of primary silicon in Al-27Si alloy refined by Si-Ti-P master alloy are smaller and more uniform. The size of primary silicon can be refined to 14.7 鹵1.3 渭 m by adding 350ppm phosphorus into Al-27Si melt by Si-Ti-P master alloy at 850 鈩，

本文編號：2414173