Study On The Microstructure And Properties Of Functional Gradient Materials Prepared By FAPAS

FAPAS,Field activated and pressure assisted synthesis,is a new process characterized by high efficiency and economy,fast reaction with low temperature that is anticipated to be applied in the field of preparation gradient composite materials and joining of different materials.In this paper,FAPAS has been applied to prepare FGM by making the composite ceramics and metal matrix bonded through a media layer,which improves the hardness and abrasive resistance of the metal surface.The component ratio and experimental parameters have been studied by preparing different system FGM such as(TiB₂)_pNi/Ni₃Al/Ni,(TiB₂)_pNi/Ni₃Al/405 stainless steel and(TiB₂)_pNi/Ni₃Al/Cu.In the experiment,scanning electron microscope,X-ray diffraction and EDS have been applied to observe and determine the microstructure and phase of each layer,to investigate the distribution of the element across the interface. And the microhardness sclerometer,abrasive tester and thermal shock test were applied to evaluate the mechanical properties of the FGM.It can be indicated as following: (1)It is feasible to prepare gradient composite with metal matrix by FAPAS with mechanical alloying.(2)The component ratio has effect on the surface hardness of the FGM. The results indicated that there is a climb of hardness from the metal matrix to the composite ceramics.Furthermore,the increase of ratio of TiB₂ in the composite made it increase greatly.(3)The current has effect on the thickness of the transitional layer.Under the action of the electric field,well metallurgic bonding forms between the composite layer,Ni3A1 intermetallic compound and Ni plate respectively. Furthermore,the elements interdiffusion exists across the interface.The thickness of the transitional layer between nickel plate and Ni₃Al intermetallic compound layer increases with the increase of current which owns to the diffusion of elements improved by the electric field.(4)the gradient composite of copper matrix prepared by FAPAS with MA has higher abrasive resistance.Its rate of wear is about 10%of that of 20Cr cemented steel.