Of Ni, Cr, Al-of Tac Eutectic In Situ Composites Microstructure And Properties Of Research,

In this paper, one high temperature gradient directional solidification apparatus with liquid metal cooling(LMC) was used. The technology parameter of preparation for Ni,Cr,Al-TaC eutectic in-situ composite was optimized. Longitudinal and transverse metallographic specimens for microscopic observation were prepared using conventional techniques. The morphology evolution was observed with NEOPHOT-1 metaloscope and AMRAY100B SEM. The volume fraction, the transverse area and the spacing of the TaC fibers are measured with Leica Quantimet 500 instrument. JEM-2000CX TEM was used to observe the -y phase. the effect of solidification rate on the solidified structure, cooperation growth zone and microstructures such as TaC rods volume fraction, TaC rods average spacing, TaC average transverse area and y phase in this eutectic composite were systematically investigated with LMC. The relationship between solidification processing controlling and solidification microstructure was established. The influence of the microstructure on mechanical property and rupture mechanism of the composite at the room and elevated temperature were discussed.It was found that the interface morphology of Ni,Cr,Al-TaC eutectic in-situ composite evolved from plan to cell and then to dendrite with the increase of solidification rate, if the gradient retained constant. In the same time, the eutectic microstructure also evolved from rod to cell and then to dendrite. Following the increase of the solidification rate, the y?phase gets smaller and smaller, and the morphology of y?phase becomes more circular. The inter-rod spacing of TaC obeys relationship with X13.18R04972, and the transverse area of TaC versus solidification rate is S=?.6597R+5. l4in this eutectic composite. The volume fraction of TaC could be changed with increasing solidification rate.The tensile strength and ductility of Ni,Cr,Al-TaC eutectic in-situ composite at room temperature is obviously improved with increasing the volume fraction of TaC and decreasing the inter-rod spacing and the diameter. The rupture mode of the composite at room and elevated temperature depends upon the work-hardening characteristics of the nickel alloy matrix.