Investigation On The Properties Of Ti₃SiC₂/Al₂O₃ Composites By Vacuum Hot Pressing Sintering

Ti₃SiC₂/Al₂O₃ composite is considered as an ideal structural material due to its good physicochemical compatibility and complementary mechanical properties with Al2O3.However,due to the narrow phase region of in-situ synthesis of Ti3_SiC₂ phase,in the in-situ preparation of Ti₃SiC₂/Al₂O₃ composite materials,it is easy to generate too much impurity phase TiC with varied phase composition,resulting in poor mechanical properties of the prepared composite materials.The main purpose of this research is to improve the mechanical properties of Ti3SiC2/Al2O3 composite materials by optimizing the sintering process and raw material system under vacuum hot pressing sintering conditions,reducing the formation of impurity phase TiC during in-situ synthesis,and improving the mechanical properties of Ti₃SiC₂/Al₂O₃ composite materials.Firstly,the hot pressing and sintering process conditions were fixed?sintering temperature 1550?,sintering pressure 30MPa,heat preservation and pressure holding time 1.5h?,and Al2O3?10%-60%?with different volume ratios were mixed with raw materials?Ti:SiC:C=3:1:1?to explore the influence of different volume ratios of alumina on the mechanical properties and phase composition of in-situ Ti3SiC2/Al2O3composites.Then,the influence of alumina admixture on the phase composition of in-situ Ti₃SiC₂/Al₂O₃ composite was investigated at different sintering temperatures.It was found that the admixture of alumina was conducive to the uniform distribution of Si elements,that is,the admixture of alumina promoted the crystallization transformation of the target composite products.The results showed that the Al element in alumina,under the condition of high temperature and high pressure,formed Al molten pool,which accelerated the diffusion and uniform distribution of Si elements,and also promoted the formation of Ti3SiC2 phase.In the preliminary preparation of Ti₃SiC₂/Al₂O₃ composite,we found that there was still a large amount of impurity phase TiC in the target product,so we selected a variety of different raw materials to optimize and screen the raw material system of Ti3SiC2 prepared by in-situ reaction method.According to the literature review and our experiment,the raw materials used include Ti/SiC/C,TiC/Si/C,Ti/Si/C/Al,Ti/Si/C/Al,and Ti/SiC/C/Al.The sintering process was determined as the sintering temperature of 1450?,the sintering pressure of30MPa,and the holding time of heat preservation and pressure of 1.5h.The experiment found that when Ti/SiC/C/Al was used as the raw material system,the content of the impurity phase TiC was the least.On this basis,a comparative study was conducted on the effect of adding sintering agent Al and whether the ratio of raw material was stoichiometric on in-situ synthesis of Ti₃SiC₂.The results showed that the Ti₃SiC₂ synthesized by the addition of sintering additive Al and the raw material of non-stoichiometric ratio?Ti:SiC:C:Al=3:1.1:0.9:0.2?had almost no TiC impurity phase when compared with the purity.The addition of sintering agent Al can make up for the heat loss of Si element in hot pressing sintering process and ensure the balance of raw material ratio.After optimization determine the raw material system,further research on the raw material particle size of vacuum hot pressing process of in situ synthesis of Ti3SiC2/Al2O3 composites mechanical properties and the effect of phase composition,the experimental results show that when raw material particle size is fine,sample more evenly,the microstructure of impurity phase TiC content decreased significantly,got more significantly improve the mechanical properties.