Microstructure And Properties Of Aluminum Matrix Composites Fabricated By In-situ Reaction Between Multivariate Oxides And Aluminum

Focused on the problems of piston make of ZL109alloy work in the poor condition, and the high temperature properties of Al-Si alloy are unstable. Al2O3p/ZL109composite is fabricated by traditional casting technique, through adding Fe2O3-CuO-CrO3/Al mixed briquetting into molten ZL109.The in situ reaction between Al and Fe2O3,CuO,CrO3and the fabrication technology of Al2O3p/ZL109composites are studied systematically in this paper.The influence of the diluent Al content to the properties and distribution of produc are also investigated. Through the test of the microstrcture and properties of the composites, the main results achieved are summarized as follows:The reaction gradient between Al and Fe2O3,CuO,CrO3is Fe2O3>CuO>CrO3,that is proved by the sintering test of the mixed compacts.The reaction product are Al2O3p and diffrent intermetallic compounds.All of the ratio of powder,briquette density,temperature of sintering and soaking time will bring influence to the reaction. The distribution of the minisize particles of Al2O3is uniform in the matrix, and the interface between the reinforcement and the matrix is clean and firm; The elements of Fe,Cu,Cr facilitate the matix alloying,and refine the primary silicon.By selecting appropriate technique,the excellent composite of Al matrix for piston is expected to be fabricated.ZL109is refined at820℃-870℃, adding the mixed compacts at780℃,results show that the structure of Al2O3p/ZL109composites is homogeneous and the mechanical properties of the composites are excellent. Mg can reduce the inducted time as the inducer of the reaction, when Mg content is3wt%, the inducted time is about one second. SEM observation show that Al2O3particles disperse in ZL109matrix, and the intermetallic compounds of reaction in-situ become hard particles of good thermal stability in the composite matrix. TEM observation show that Al2O3p generated by reaction in-situ is approximate shape of the oval, the size of the paticles is about0.1μm. When the contents of Fe,Cu,Cr reach to0.656wt%、1.407wt%、0.1419wt%respectively, the hardness of the composite improve1.9%than the matrix, the abrasion resistance enhance2.93%at room temperature, the coefficient of friction reduce28.6%at300℃, the highest tensile strength can reach as high as178MPa at300℃holding half hour, the average tensile strength improve7.9%at300℃. It is well solved the problem of instability of the high temperature performance of ZL109. Although the room temperature tensile strength of the composites is decreased, the comprehensive performance are excellent, and meet with the requirements of composite piston use.