高硅铝合金中TiP的演变行为与初晶Si复合形核研究
发布时间：2019-01-23 20:41
【摘要】：本文采用两种方法提高初晶硅异质形核效率,实现高硅Al-Si合金有效细化。一种是制备高含磷量的Si-Ti-P系中间合金,分析中间合金的相组成及其在Al-Si熔体中的演变过程,并以此为依据设计Si-Ti-P系中间合金的使用参数。对比Cu-14P、Al-3P、Si-Ti-P系中间合金对Al-27Si合金的细化效果,并讨论磷细化处理对Al-27Si合金的热膨胀系数和拉伸性能的影响。另一种是改进细化工艺,同时引入AlP和TiB_2粒子,验证TiB_2@AlP复合粒子对Al-45Si合金的细化效果,并提出吸附形成机制。本文主要研究工作如下:(1)Si-Ti-P系中间合金在Al-Si熔体中的演变行为分析了 Si基合金中磷化物的存在形式。研究发现,通过向Si-Mn-P合金中引入过渡族金属元素Ti、Fe、Cu,可促使原Si-Mn-P合金中的磷化合物发生转变。在Si-P系合金中,过渡族金属元素的"固磷"效果不同。Si-Ti-P系中间合金中,磷化物主要为TiP相。在Al-Si熔体环境下,中间合金中的TiP相与Al-Si熔体发生反应,产物为AlP和(Al,Si,Ti)三元化合物。研究发现,TiP相与Al-Si熔体间会发生化学势差驱动的液-固扩散反应。将Si-Ti-P系中间合金加入到Al-Si熔体后,硅基体首先熔解,使TiP相与铝熔体接触。在化学势差驱动下,TiP演变为AlP,此演变的反应速率受扩散控制。因此使用Si-Ti-P系中间合金细化处理Al-Si熔体时,需要一定的保温时间来获得较好的细化效果。提高反应温度,增加熔体对流等可加快TiP相向AlP相演变,缩短保温时间。(2)Si-Ti-P系中间合金对过共晶Al-Si合金的细化行为与Cu-14P和Al-3P相比,使用Si-Ti-P系中间合金细化后的Al-27Si合金中初晶硅尺寸更细小,形状更规整,分布更均匀。通过Si-Ti-P系中间合金向Al-27Si熔体中加入350ppm磷,在850℃保温_20分钟,初晶硅尺寸可细化至 14.7±1.3μm。对磷细化前后的Al-27Si合金进行热膨胀系数和拉伸性能进行测试,发现磷细化处理有助于降低Al-27Si合金的热膨胀系数并提高合金的拉伸性能。使用Si-Ti-P系中间合金细化处理Al-27Si合金后,合金的热膨胀系数降至16.25×10-6/K。与未细化的合金相比,极限拉伸强度和延伸率分别提高106%和235%。(3)AIP复合粒子对高硅Al-Si合金的细化行为完善了TiB_2@AlP形成机制,验证了TiB_2@AlP粒子对Al-45Si合金中初晶硅的细化效果。在Al-Si熔体中,P原子倾向于吸附在TiB_2表面形成富磷的吸附层,在过冷度的驱动下富磷吸附层转变为AlP,形成复合的TiB_2@AlP粒子。密度泛函理论计算显示,P原子更易于被吸附在以Ti终止的(0001)TiB_2界面上,并且倾向于靠近Ti原子。与单独引入AlP相比,引入TiB_2@AlP粒子对Al-45Si合金有更好的细化效果。在1300℃保温5分钟后,初晶硅尺寸可细化至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 卤1.3 渭 m by adding 350ppm phosphorus into Al-27Si melt by Si-Ti-P master alloy at 850 鈩，
本文编号：2414173
[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 卤1.3 渭 m by adding 350ppm phosphorus into Al-27Si melt by Si-Ti-P master alloy at 850 鈩，
本文编号：2414173
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