Preparation And Mechanical Properties Of In-situ Reactive Composite In The System Of Al-K₂ZrF₆-B₂O₃

(ZrB₂+Al₂O₃+Al₃Zr)/Al and (ZrB₂+Al₂O₃+Al₃Zr)/A356 matrix composites were firstly prepared from the novel Al-K₂ZrF₆-B₂O₃ system via in-situ melt reaction. The microstructure, solidification behaviors, reaction mechanism and mechanical properties of the as-prepared composites were investigated.XRD, EPA and SEM show that ZrB₂, Al₂O₃ and Al₃Zr reinforcement particulates have been obtained; the reinforcement particulates were distributed nearly uniformly in the matrix and the average size was about 1-4μm. The best processing parameters of the Al-K₂ZrF₆-B₂O₃ composites according to the surface analysis of the solidifying structure were described as follows: the initial reaction temperature is 850±20℃, the reaction time 15 min., the mole ratio to the reactant K₂ZrF₆ and B₂O₃ 2:1 and the additional amounts of the reactants no exceeding 20% in weight than the total of the aluminum molten.The tensile strength of the (ZrB₂+Al₂O₃+Al₃Zr)_p/Al composites increase with the increase of the volume fraction, the elongation increase firstly and then decrease. When the volume of particulate is 8vol%, σ_b and σ_s increase by 95.2% and 167.3% to the aluminum matrix, reaching 152.3 and 112.3MPa, respectively. The tensile and yield strength of the (ZrB₂+Al₂O₃+Al₃Zr)_p/A356 composites increase with the increase of the volume fraction and the elongation decrease. When the volume of particulate is 8vol%, σ_b and σ_s increase by 53.3% and 68.4% to the aluminum matrix, reaching 341.6 and 283.2MPa, respectively.The wear resistance of the as-prepared Al and A356 matrix composites increases with the increase of the volume fraction under the following dry sliding condition at room temperature: 58.8N load and 0.42m/s sliding rate of speed. When the sliding time is 120min., the wear mass of the pure aluminum and A356 alloy is 2.1 fold and 2.6 fold to 59.2mg and 31.2mg for the 8vol% (ZrB₂+Al₂O₃+Al₃Zr)_P/Al and (ZrB₂+Al₂O₃+Al₃Zr)p/A356 composites, reaching 122.2mg and 82.2mg, respectively.With the sliding time increase, the (ZrB₂+Al₂O₃+Al₃Zr)p/A356 composites showed better wear resistance than that of the A356 alloy. The wear mass of the composites and the matrix increase with the increase of the forcing load under the sliding conditions: 0.42m/s sliding rate of speed and 60min. sliding time with the same load. The...