Research On Preparation,Microstructure And Properties Of TiC-Ti₅Si₃/Cu Matrix Composites By Casting Method

High-strength wear-resisting copper alloy has excellent mechanical properties,corrosion resistance,thermal conductivity and outstanding wear-resisting properties,which is mainly used in automobile synchronizer gear rings,heavy-duty high-speed hydraulic rotors,bearings and various precision high-strength wear-resisting forging parts and other important components.The formation of stable hard phase with suitable size and morphology and uniform distribution on the matrix is the key to ensure its excellent performance.Both Ti C and Ti₅Si₃ have high hardness,elastic modulus and other properties,which are excellent reinforcements for high-strength wear-resistant copper alloys,and their morphology is quite different in copper.Therefore,hybrid reinforcement of Ti C and Ti₅Si₃ is a feasible scheme to prepare high-strength and wear-resistant copper matrix composites with excellent comprehensive properties.In this paper,Ti C-Ti₅Si₃ hybrid reinforced copper matrix composites were successfully prepared by casting method by the reaction of Ti and Si C in copper melt,and the microstructure and properties of the hybrid reinforced copper matrix composites were further improved by hot rolling.The high strength and wear resistant copper matrix composites with good properties were successfully prepared.First,Based on Cu-Ti-Si C system,the intermediate products of Cu-Ti-Si-C reaction were obtained by controlling temperature and reaction time,and the reaction mechanism of Ti-Si-C was analyzed.Research shows that Ti and Cu react firstly to form Cu-Ti liquid phase in Cu-Ti-Si C system.Subsequently,the reaction between Ti（l）and Si C starts.There are two paths for the reaction between Ti（l）and Si C.One path is that when the reaction temperature is low or the particle size of Si C is large,Si C will be converted into graphite due to the outward diffusion of Si.Then,the Si C-derived graphite reacts with Ti（l）to form Ti C.The Ti C formed by this pathway is easy to agglomerate.Another path is when the reaction temperature is high or the Si C particle size is small,Ti（l）reacts directly with Si C to form Ti₃Si C₂ phase,which is then decomposed to form Ti C_x and Ti-Si phase,and finally transformed into Ti C_y（x>y）and amorphous or Crystal Si.Due to the effect of Ti-Si phase or Si phase,the distribution of Ti C formed by this path reaction is more uniform.Secondly,the microstructure analysis of the prepared Ti C-Ti₅Si₃ hybrid reinforced copper matrix composite material shows that the Ti₅Si₃ in the composite material is intertwined in the copper matrix to form a bird’s nest-like space skeleton structure,and Ti C is attached to the Ti₅Si₃ skeleton or distributed in the skeleton.Hot rolling can fragment the reinforced phase of Ti₅Si₃ in copper matrix composites,leading to the destruction of the space skeleton structure of Ti₅Si₃,but it can improve the dispersion of Ti C and Ti₅Si₃ in copper matrix.In addition,although hot rolling can disperse Ti C agglomerates,part of Ti C is still distributed on the copper matrix in small agglomerates.Thirdly,the research on the wear resistance of the prepared Ti C-Ti₅Si₃ hybrid reinforced copper matrix composites shows that the addition of Ti₅Si₃ and Ti C can improve the wear resistance of composites.As the volume fraction of Ti₅Si₃ increases,the wear resistance of Ti₅Si₃ reinforced copper matrix composites gradually increases,and the wear mechanism gradually changes from severe delamination wear and abrasive wear to abrasive wear and adhesive wear.With the increase of the volume fractions of Ti C and Ti₅Si₃,the wear resistance of Ti C-Ti₅Si₃ hybrid reinforced copper matrix composites increased first and then decreased.As the load gradually increases,the wear resistance shows a trend of first decreasing and then increasing,and reaches the lowest when the load is 7.35N.The wear mechanism is severe delamination wear and adhesive wear.With the increase of the volume fraction of Ti C and Ti₅Si₃,the delamination wear weakens and the adhesive wear intensifies.Finally,the research on the tensile properties of the prepared Ti C-Ti₅Si₃ hybrid reinforced copper matrix composites shows that the introduction of Ti₅Si₃ and Ti C can improve the tensile strength of composites.The tensile strengths of Ti₅Si₃ reinforced copper matrix composites can reach up to 248.22MPa,and the strength after hot rolling reaches 414.32MPa.The fracture mode is mainly ductile fracture,and there is also cleavage fracture.As the volume fraction of Ti₅Si₃ increases,the fracture mode gradually changes from ductile fracture to cleavage fracture.The tensile strengths of Ti C-Ti₅Si₃ hybrid reinforced copper matrix composites reaches 251.40MPa,and the strength after hot rolling is 424.05MPa.The fracture mode is mainly ductile fracture,and there is also cleavage fracture,and cracks appear at Ti C aggregate.With the increase of the volume fraction of Ti C and Ti₅Si₃,the fracture mode gradually changes to cleavage fracture.In addition,hot rolling can significantly improve the plasticity and toughness of the composites,and the fracture mode of Ti₅Si₃ reinforced copper matrix composites after hot rolling becomes ductile fracture.The fracture mode of Ti C-Ti₅Si₃ hybrid reinforced copper matrix composites is mainly ductile fracture.