Preparation And Mechanical Properties Of In Situ Synthesised Composite In Al-Si-K₂ZrF₆ System

The novel(Al₃Zr+Si)_p/Al matrix composites are prepared by in-situ melt reaction from Al-2OSi and K₂ZrF₆.The solidification microstructure,in-situ particulate features of the prepared composites have been investigated by using Optical Microscope(OM),Scanning Electron Microscope(SEM),Electron Probe Microanalyzer(EPMA),X-ray Diffractometer(XRD) and other modem equipments. Mechanical properties and wear property have also been tested.The nature and mechanism of these characteristics have been analyzed.The optimum parameters of the formed composites in the Al-2OSi-K₂ZrF₆ system are that the initial reaction temperature is about 800℃,the reaction time is 15 minutes,the mass fraction of the adding reactant is 15%of the melt aluminum.The XRD and SEM analyses indicate that the synthesized practices are Si and Al₃Zr. These practices are free and well-distributed in the aluminum matrix.The average size of the primary silicon is about 20μm,while that of Al₃Zr reinforcement particulates is about 5μm.After multiple modified by P-Cu and RE,the size of primary silicium are more refined.Results of mechanical property testing show that the tensile strength and hardness of(Al₃Zr+Si)p/Al composites are higher than that of its matrix alloy, respectively,and increased with the increase of the volume fraction,but the elongation decreased.With 5.5vol%of in-situ particulates,the values forσb and HB have been increased by 41.6%and 39.7%of those of Al-2OSi,to 194MPa and 95, respectively.The tensile fracture morphology and mechanism of(Al₃Zr+Si)p/Al composites are observed and analysed.Results indicate that the fracture mechanism is brittle fracture and the strengthening mechanism of in-situ Al₃Zr particles reinforced aluminum matrix composites include reinforcement phase strengthening,solid solution strengthening and finer crystal strengthening.Dry sliding wear tests at room temperature show that the wear resistance of the composites is superior to that of its matrix alloy.The wear mechanisms of the composites determined by SEM microstructures of the wear surface and subsurface show that the wear mechanisms of the composites is adherence wear and abrasion wear.Under the same load,the wear mechanism transforms from adherence wear and abrasion wear to abrasion wear with the increase of the volume fraction of the reinforced particles.Under the same volume fraction of the reinforced particles,the wear mechanism transforms from abrasion wear to adherence wear and abrasion wear with the increase of the load.