粉末冶金TC4-PCS复合材料的热变形行为

Hot deformation behavior of TC4-PCS composites by powder metallurgy

以聚碳硅烷(PCS)为前驱体,采用粉末冶金无压烧结制备原位自生颗粒增强的TC4复合材料。通过Gleeble-3500热模拟试验机对TC4-1PCS(PCS的质量分数为1%)复合材料进行850~1100℃,0.001~1 s^(-1)的模拟热压缩实验,分析不同参数下复合材料的应力-应变曲线。采用OM,SEM和EBSD等手段分析变形参数对增强相颗粒、基体组织和致密化的影响。结果表明:热变形前TC4-1PCS复合材料存在较多残余孔隙,TiC增强相颗粒尺寸约为5~10μm。TC4-1PCS基体的β转变温度(T_β)介于1000~1050℃之间,在T_β以上进行变形时,TC4-1PCS基体全部为片层状淬火马氏体,而在T_(β)以下变形后基体为双态组织。变形温度决定复合材料的致密度和组织类型,应变速率影响基体相尺寸和残余孔隙率。变形温度的提升和应变速率的降低可以促进TC4^(-1)PCS复合材料的致密化,应变速率的提高对细化组织效果明显。在1050℃,0.1 s^(-1)下变形可以较大程度实现TC4-1PCS复合材料组织细化和致密化。

The in-situ synthesized particle reinforced TC4 matrix composites were prepared by powder metallurgy pressureless sintering using polycarbosilane(PCS)as precursor.The thermal compression simulation experiments were conducted on TC4-1PCS(mass fraction of PCS is 1%)composites at 850-1100℃and 0.001-1 s-1 to analyze the stress-strain curves of the composites under different parameters using the Gleeble-3500 thermal simulation testing machine.The effects of deformation parameters on the reinforced phase particles,matrix structure and densification were analyzed by OM,SEM and EBSD methods.The results indicate that the TiC reinforced phase particles with the size of 5-10μm and large amount of residual pores are observed in the TC4-1PCS composites before hot deformation.Theβtransition temperature(Tβ)of TC4-1PCS matrix is 1000-1050℃.When deformed above Tβ,matrix of composite consists of lamellar quenched martensite,while the matrix turns into duplex microstructure,when deformed below Tβ.The deformation temperature determines the relative density and microstructure types of the composites,while the strain rate affects the phase size in the matrix and residual porosity.The densification of TC4-1PCS composites can be promoted by the increase of deformation temperature and the decrease of strain rate,while the increase of strain rate has obvious effect on the microstructure refinement.The microstructure refinement and densification of TC4-1PCS composites can be achieved by the deformation at 1050℃and 0.1 s-1.