Research On Microstructure And Properties Of In-situ Synthesized Multiple Phase（TiB,TiC,Ti₅Si₃） Hybrid Reinforced Ti555 Titanium Matrix Composite Prepared By SPS

In this paper,Ti555 titanium alloy was used as the matrix,the composition is similar to Ti55531.A new type of in-situ synthesized multi-phase（TiB,TiC,Ti₅Si₃）hybrid reinforced titanium matrix composites were prepared by SPS.The microstructure and properties of the materials were analyzed,and the effect of heat treatment on the microstructure and properties of the materials were explored.The main research and results are as follows:（1）The effects of different contents of B4Cp（1.75⁵.25 vol.%）on the composites were studied.It was found that B4Cp can refine the particle size of the mixed powder.The phases of the sintered composite mainly include Ti,TiB and TiC.When the B₄C_p content increase,the grain of the composite was smaller,and the apparent porosity and microhardness were also increased.The apparent porosity of the composite with 5.25vol.%B4Cp was the highest,about5.02%,and the microhardness was also the highest,which was 928.27HV,about 72.15%higher than that of the matrix alloy.（2）The microstructure and properties of the composites with various reactants（3.5vol.%B₄C_p+1.5vol.%CNT or SiC_p）were studied.The results show that the phases of the sintered composites were different.The phases of the composite with B₄C_p+CNT were very similar to that with B₄C_p,but the TiC content increases,and the composite with B₄C_p+SiC_p contains Ti₅Si₃and TiSi,besides Ti,TiB and TiC.The grain of the composites with two reactants were refined,and the apparent porosity increased.The composite with B4Cp+CNT has the smallest grain size,the highest apparent porosity is 5.89%,and the highest hardness,about 1243.36HV.（3）The effects of different heat treatments on composites were studied.The results show that the phases of the composite with 3.5vol.%B4Cp did not change before and after heat treatment,but the content of the reinforced phase increased,and composite has the best performance at solid solution 920℃for 3h and aging at 600℃for 8h.After heat treatment,the microhardness of the composites prepared with two reactants increased obviously,and the microhardness of the composite with B4C_p+CNT was the highest,1327.42HV,and the compression strength at room temperature was also the highest,1002.36Mpa,about 53.32%higher than that of the matrix.（4）The high temperature oxidation behavior of material after heat treatment were studied.The results show that the oxidation products of the matrix alloy and composites with B₄C_p and B₄C_p+CNT were very similar and were mainly TiO₂ and Al₂O₃,while the oxidation products of the composites with B₄C_p+SiC_p includes SiO₂,besides TiO₂ and Al₂O₃.The density of the oxide layer of the matrix,composites with B₄C_p,B₄C_p+CNT and B₄C_p+SiC_p increased gradually,and the thickness of the oxide layer were 56μm,42μm,32μm and 38μm respectively.In general,the oxidation resistance of the matrix alloy is weak.The oxidation resistance of the composites were significantly improved compared with matrix allooy.The composite prepared by adding B₄C_p+SiC_p has the best oxidation resistance.（5）The hot corrosion behavior of composites after heat treatment were studied.It is found that the main corrosion products of the matrix alloy,the composite materials with B₄C_p and B₄C_p+CNT were Al₂O₃,TiO_2,NaTiO₂ and TiS₂,while the composite materials with B₄C_p+SiC_p,SiO2 were detected.The weight gain and corrosion depth of the matrix,B4Cp and B4Cp+CNT and B4C+SiCp decreased gradually,with the corrosion depth of 49μm,37μm,14μm and 23μm,respectively,indicating that the corrosion resistance of the composite was gradually enhanced,and the composite with B₄C_p+SiC_p has the best corrosion resistance.In summary,this paper used spark plasma sintering method to prepare in-situ synthesized multiple phase（TiB,TiC,Ti₅Si₃）hybrid reinforced titanium Ti555 Titanium matrix composites by adding different contents and various reactants（B₄C_p,CNT and SiC_p）.It was found that titanium matrix composite prepared by adding two reactants had better comprehensive properties.The specific is that the hardness of titanium matrix composite prepared by adding B₄C_p+CNT is the highest before and after heat treatment,and the compression property at room temperature is the highest after heat treatment;while the titanium matrix composite prepared by adding B₄C_p+SiC_p has the best high temperature oxidation resistance and hot corrosion resistance.