Study On Melt Infiltration Behavior Of Lamellar-interpenetrated SiC/Al Composites During Preparation

The SiC/Al composite prepared by the freeze casting method combined with the melt infiltration process has good strength and toughness.However,due to the extremely poor wettability of SiC ceramics and Al substrates,complex interfacial reactions are involved in the infiltration process.Reasonable control of interface reaction and study of its infiltration behavior are critical to improve the performance of composite materials,so it has always been a hot and difficult point in the study of melt infiltration process.Current research has shown that layered aluminum matrix composites have excellent performance,but their properties are determined by special microstructure and impregnation behavior control.Reasonable control of impregnation behavior is especially important for improving composite properties,Therefore,it is very necessary to further understand the infiltration behavior during the preparation of composite materials,especially the study of infiltration process and the effect of infiltration kinetics on the melt infiltration process.In this paper,SiC/Al composites were prepared by freeze casting combined with melt infiltration.The surface state of the pretreated lamellared SiC preform,the improvement of the microstructure of the preform,the infiltration process of the melt and the impregnation behavior were studied in order to prepare the melt infiltration process of the SiC/Al composite.For reference.The main findings of this paper are as follows:?1?The SiC/Al composites were successfully prepared by the freeze casting method-melt infiltration process.The alloy layer and the ceramic layer were alternately arranged.The SiC/Al composites were completely impregnated and the interface was well bonded.The microstructure was very good.The layered gradient structure in the SiC ceramic preform is well preserved.?2?The intrinsic condition of infiltration depends on the dual action of the active element Mg and the infiltration atmosphere N₂.?3?The SiC particles have significantly improved the impregnation effect after oxidation and sintering.The porosity of preforms with solid phase content of 10 vol.%,20 vol.%and 30 vol.%were:91.3%,80.9%,70.7%,respectively.The impregnation rate of Al-Si-Mg alloy in layered SiC preforms The solid phase content is gradually slowed down,and the average infiltration rate during 950?is 22.2?m/min,16.7?m/min,and 14.8?m/min,respectively.?4?During the infiltration and heat preservation period,the infiltration process is mainly divided into five stages:alloy melting stage,incubation period,alloy liquid infiltration into layered SiC preform particles,alloy liquid infiltration into layered SiC preforms.The alloy liquid is filled with minute pores between the layers.The infiltration area of the solid content of 20 vol.%and the glycerin content of 6 vol.%at3h,3.5h and 4h are:10%,90%,100%;the insulation time at the temperature of 900?,950?,1000?impregnation is:4.5h,4h,3h.?5?The interface analysis of the unimpregnated complete sample shows that the impregnation occurs preferentially between the layered SiC preform particles,and as the interfacial reaction occurs,a negative pressure is formed between the layers.Under the action of gravity and capillary force,it spontaneously infiltrates into the layers,and the infiltration continues to advance.The interface products are MgAl₂O₄ and Mg₂Si.?6?SiC/Al composites can be obtained by extrusion impregnation process and pressureless infiltration process,and no unfavorable brittle phase is generated by controlling the process parameters.