The Residual Internal Stress Of TiCp Particles Reinforced Titanium Matrix Composites To Contribute To Mechanical Properties

In the developing course of metal materials, the residual internal stresses in parts, which come from all sorts of factors, strongly affect the fatigue property, the dimension stability and application life of material. For particle reinforced titanium matrix composites, TiC particle became an important reinforcement in respect that which possesses better chemic and thermo-stability with titanium. However, it exists the un-match in configuration and thermodynamics between TiC particle and titanium matrix, especially the un-match of thermo-expand coefficient will results composites occur the strong internal stress when the composite is cooled from the fabricated temperature or heat treated one, which can also significantly affect mechanical properties of composite.The internal stress analysis technique by X-ray diffraction is able to measure the internal stress non-damagingly and simply. This paper performed the internal stress analysis of different heating treatment condition for three TiC particle reinforced titanium matrix composite (i.e.Ti6A14V+7wt%TiC(T64), Ti3A12.5V+7wt% TiC (T32)and Ti5A12.5 Sn 2Zr 0.5MoNb+3wt%TiC(T650)) used the X-ray diffraction Sin2 V method, and studied how the internal stress affected the mechanical properties of composite, the essential relation between stress and strain of composite, the internal stress distributed to strengthening dislocation and influenced the fracture mechanism of composite.(1) The internal stress been measured in different heating treatment condition for three TiC particle reinforced titanium matrix composite by the X-ray diffraction sin2 Ψ method, resulted in the composites will induce the different character internal stress above and under 800℃ or so, and which will increase with heating treatment temperature elevating. Otherwise, the transferring point of internal stress character will change litter with titanium matrix varying. According to Eshelby model, the transferring point results from thermo-expand coefficient of TiC particle and titanium matrix vary with temperature change.(2) The tensile strength, fatigue strength and impact of composites will increase withinternal stress increasing, which results from TiC particle became the main load phase in composite, and needs the more significant load so as to the composite fielding and internal stress relax.(3) The study of essential relation between stress and strain of composite results in the reinforcement and matrix possess the different loading with deformation going on, and internal relaxing rate will decrease with strain increasing.(4) The study of dislocation of composites indicates it was a other strengthening factor to composite as internal stress relaxing to increase the density of dislocation in titanium, besides the modulus strengthening, non-match strengthening of interface, etc.(5) The TiC particle affects the fracture of composite indicated the crack's origination and spreading is greatly correlative to particle character. The origination of crack can occur from fault of particle, the interface between particle and titanium matrix, and the internal stress existing in matrix can offer the dynamical for crack spreading. Otherwise, the compressive stresses induced on particle and compressive stress along radial of sphere particle in matrix will restrain the crack to spread in stage of crack's spreading of slow speed.