The Research Of High-entropy-alloy/Cu Composite

Copper matrix composites can be used widely in aviation, aerospace, military and rocket engines, etc. High entropy alloy is a recently developed and a new alloy. It has high strength, high hardness and high temperature stability performance. In order to understand the performance of high-entropy-alloy/Cu composites, an equiatomic AlFeCrCoNi high entropy alloy strengthening phase was synthesized by arc melting method and mechanical alloying, and the high-entropy-alloy/Cu composite materials is synthesized by powder metallurgy method. The effect of powder process of high entropy alloy, the sintering process and the strengthening phase content on microstructure and properties of high-entropy-alloy/Cu composites are systematically analyzed by means of metallographic microscope, scanning electron microscopy, hardness test and compression test,etc.The element metal powders of Al, Fe, Cr, Co, Ni are mixed in equiatomic composion and milled in planetary ball miller for 18 h at 300 rpm in argon atmosphere. Stainless steel vials and balls are utilized as the milling media with a ball-to-power ratio of 10:1, and N-heptane is the process control agent to avoid cold welding as well as to prevent the alloy from oxidizing. By using the above parameters, AlFeCrCoNi high entropy alloy is prepared successfully and its grain size is 58 A. It is found that the annealing time at 800℃ has no effect on crystal structure and phase transformation of high entropy alloy.An equiatomie AlFeCrCoNi high entropy alloy is synthesized by arc melting method. Its lattice constant is a=b=c=2.877, the melting point is 1384.3℃, the compression yield strength is 1290 MPa, and the compression fracture strength is 2310 MPa. The fracture morphology is the cleavage step and river pattern, and thefracture mechanism is cleavage fracture. BCC1, BCC2 and HCP phase are found at annealing on 800℃ in AlFeCrCoNi high entropy alloy.With the content of AlFeCrCoNi high entropy alloy increasing in Cu matrix composites, the density and conductivity gradually decrease, but hardness increases, compressive strength increases firstly and then decreases. With sintering temperature and sintering pressure increasing in Cu matrix composites, density, hardness, and compression strength increase, but the conductivity decreases. The preparion parameters of Cu-20 wt.% AlFeCrCoNi composite materials with good performance are milling time 74h (12 min stop 6 min) by 350 rpm in argon atmosphere, sintering temperature 973 K, sintering pressure 100 MPa, and pressure time 2 hours.The AlFeCrCoNi high entropy alloys is by arc melting and then cutted into slices. The slices are milled in planetary ball miller at 400 rpm and ball-to-power ratio of 40:1 in argon atmosphere, and then the particle size is 1-5μm. When Cu-20 wt.% AlFeCrCoNi composite materials are prepared under 973 K and 100 MPa for 1 hour, the compression yield strength of Cu mixed composite is 310 MPa, which is increased by 1.38 times compared with pure copper, and the compression rate is more than 60%.