Research On Forming And Properties Of High Entropy Alloy/Ceramic Composite Lattice Structure

High entropy alloy/ceramic composite lattice structure has shown great advantages in the fields of impact protection,thermal insulation and shock absorption.The combination of high-toughness and high-entropy alloy materials and high-strength ceramic materials forms a lattice structure with energy absorption effect,which can manufacture a composite with anti-penetration performance and has a wide application prospect in the fields of aerospace,military armor and coal mine safety.In this thesis,the lattice structure preform of FeCoCrNiAl high entropy alloy(HEA)prepared by selective laser melting(SLM)was compounded with the slurry of SiC and FeCoCrNiAl mixed powder by gel casting,and the sintered body of high entropy alloy/ceramic composite lattice structure was obtained after degreasing and oscillating pressure sintering.This thesis focuses on the influence of laser process parameters on the formation of lattice structure of high entropy alloy,analyzes the influence of gel curing,drying shrinkage of green body and rheological characteristics of slurry on gel injection molding process,and expounds the relationship between oscillating pressure sintering process conditions-microstructure-mechanical properties of composites.The main conclusions are as follows:(1)FeCoCrNiAl high entropy alloy lattice structure additive manufacturing and forming.The optimum window of laser power,scanning speed and bulk energy density for selective laser melting forming of high entropy alloy is sought.By optimizing the laser process parameters,the comprehensive quality of the formed samples is improved.With the increase of laser power,the viscosity of the melt in the micro-molten pool decreases and the wettability of the liquid phase is improved,but when the laser power is too high,microcracks and holes occur.When the laser power reaches 170 W,the relative density of SLM molding material reaches 99.05% and the compressive strength is 114.90 MPa.(2)Preparation of SiC ceramic-based composite slurry with high solid content,low viscosity and excellent stability.The effects of solid content and temperature on the drying shrinkage mechanism of green body were analyzed.It is concluded that with the increase of initiator content and temperature,the induction period and curing time of slurry polymerization are shortened.When the milling time increases,the amount of organic monomer increases and the solid content decreases,the viscosity of the composite slurry decreases.Finally,the ceramic slurry with high solid content of 56Vol% and viscosity of 365 m Pa·s was prepared.(3)The preparation and properties of FeCoCrNiAl/SiC composite lattice structure sintered body were studied.A composite lattice structure sintered body was prepared by combining selective laser melting,gel injection molding,thermal degreasing and oscillating pressure sintering.With the increase of oscillation pressure to 20 ± 5 MPa,the number of pores in high entropy alloy/ceramic sintered body is obviously reduced,and there are no coarse cracks.The interface between the two phases is dense and the boundary is obvious,and the relative density reaches 91.2%.The compressive strength of FeCoCrNiAl/SiC sintered body is 432 MPa,which belongs to brittle fracture.There are 64 pictures,12 tables and 102 references in this thesis.