Al-LaB6 alloy was successfully prepared by aluminum melt reaction method. Microstmcture analysis of this alloy was carried out by field emission scanning electron microscopy （FESEM）, Raman spectroscopy and transmission electron microscopy （TEM）. It was found that cubic LaB6 particles were highly dispersed in aluminum matrix with a uniform edge length of about 4.5 μm. Grain refining potency of LaB6 on commercial pure aluminum was also investigated. It was shown that LaB6 could act as an effective and stable nucleation substrate for α-Al during solidification process, due to their crystallographic similarity. The coarse grains of commercial pure aluminum were obviously refined to small equiaxed ones by addition of 0.5% Al-5LaB6 alloy at 720 ℃.
In this work, in-situ CaB6 reinforced aluminum matrix composites were fabricated, and the microstructure, resistivity, microhardness and coefficient of thermal expansion (CTE) of Al-CaB6 composites were studied. It is found that CaB6 compounds can be formed by reducing reaction occurred in the Al melt: . CaB6 exhibits a hexahedron morphology and distributes uniformly in the Al alloy matrix. The resistivity of Al-CaB6 composites is 3.02*10-8 Ω·m, which is close to that of pure Al and lower than that of 6063Al/Ga composites. The average microhardness of Al-CaB6 composites can reach 1270 MPa, 259.8% higher than that of pure Al. Compared to pure Al, the CTE of Al-CaB6 composites is much lower.
In this paper,the influence of deformation on the microstructure and low-temperature refining behavior of Al-3.5P master alloy was investigated.The results show that the average size of AIP particles can be reduced obviously from 15.3 μm to about 2.1 μm by deformation.However,it exhibits entirely opposite influence on refining performance when A1-3.5P master alloy was deformed at room temperature and high temperature,respectively.Only when Al-3.5P master alloy was subjected to thermal deformation,can an improvement of low-temperature refining performance be obtained.In this condition,primary Si in A390 alloy can be refined from 137 to 21 μm,making it a potential candidate for die casting production.A mechanism associated with the transformation of particle-matrix interface during deformation has been proposed and further experiment has been designed to validate it.
Huan QiaoXiangzhen ZhuTong GaoYuying WuXiangfa Liu
