多元不混溶合金凝固过程及微合金化元素影响

Generally immiscible alloys show a solidification microstructure with serious phase segregation due to the liquid-liquid decomposition. Researches in recent years indicate that 1) the nucleation behavor of the minority phase droplets has a dominating effect on the microstructure formation of these alloys; 2) rapid solidification and continuous solidification techniques have great potential in the manufacturing of monotectic alloys. Considering that reducing the interface energy between the two liquid phases or precipitating before the liquid-liquid decomposition some particles which may act as the heterogeneous nucleation sites of the minority phase droplets can promote the nucleation of the droplets, this project will study the solidification behavor of the multi-component immiscible alloys of AlBi(Pb) and Cu(Co,Cr) systems, which have a strong industry application background, as well as the effects of micro surface active elements and compound forming elements. The detailed research contents include: Carry out rapid continuous solidification experiments and gas atomization rapid solidification experiments with the multi-component AlBi(Pb) and Cu(Co,Cr) system alloys; Develop the numerical models describing the solidification microstructure formation in the multi-component AlBi(Pb) and Cu(Co,Cr) system alloys; Calculate the microstructure formation mechanisms and the effect of the micro-alloying element on the solidification processs. This research will show the possibility to control the solidification process and manufacture dispersed composites of immiscible alloys by using the micro-alloying method.

液态组元不混溶合金凝固时存在液-液相变过程，极易发生相偏析。研究表明：1)弥散相液滴形核行为决定着该类合金能否形成弥散型凝固组织；2)快速连续凝固和快速凝固适于该类合金凝固过程研究和工业制备。据此，考虑到添加某些微量元素可降低两液相间界面能或保证在液-液相变前先在熔体内析出可供弥散相液滴异质形核的化合物颗粒，促进液滴形核，本项目拟以应用背景较强的Cu(Co,Cr)、AlBi(Pb)系为代表，研究多元不混溶合金凝固行为及微量表面活性元素和化合物颗粒形成元素的影响。研究包括：实验研究多元AlBi(Pb)、Cu(Co,Cr)系合金的快速连续凝固和气体雾化快速凝固行为；建立多元AlBi(Pb)、Cu(Co,Cr)系合金凝固模型，结合实验开展模拟，揭示多元AlBi(Pb)、Cu(Co,Cr)系合金凝固组织形成机理及微量元素的影响，探明用微合金化法控制不混溶合金凝固过程、制备弥散型复合材料的可行性。

以Al(Bi,Pb)系轴瓦合金和Cu(Co,Cr)系电工合金为代表，实验研究了多元不混溶合金的凝固过程(如连续凝固过程、真空喷铸快速凝固过程等)及微合金化元素和微量化合物质点的影响。建立了描述微量表面活性元素和化合物异质核心作用下不混溶合金液-液相变过程中组织演变的模型。模拟与实验相结合，揭示了Al(Bi,Pb)系合金和Cu(Co,Cr)系合金凝固组织形成过程及微量元素或微量化合物粒子(X)的影响机理，探明了用微量表面活性元素或微量化合物质点控制液态组元不混溶合金凝固过程、制备弥散型复合材料的可行性；确定了适合用于控制Al(Bi,Pb)系轴瓦合金的微量表面活性元素(如Sn)和微量化合物质点(如TiC)；确定了适合用于控制Cu(Cr,Co)系电触头合金的微量表面活性元素Pb、Ce、Bi和微量化合物质点TiC、TiB2、Cr3C2等；利用添加微量表面活性元素或微量化合物质点的方法成功制备了第二相粒子弥散分布于铝基体的Al(Bi,Pb)系合金复合材料和富(Cr,Co)粒子弥散分布于Cu基体的Cu(Cr,Co)合金复合材料。.就以上研究，在Acta Mater, Scripta Mater等期刊上发表论文19篇(SCI收录16篇，EI收录16)；做国际会议邀请报告5次，做国内会议邀请报告3次；承办国内学术会议1次；申请国家发明专利11项，其中5项已授权；培养博士生4名(毕业4名)、硕士生2名(毕业2名)。