Fabrication And Property Of Aluminum Matrix Composites Reinforced By High Entropy Alloy

Particle reinforced aluminum matrix composites have excellent mechanical properties, such as high specific strength, high specific modulus, wear resistance. However, traditional ceramic particle reinforced aluminum matrix composites have poor ductility and toughness that limit its application in structural materials. How can get good ductility and toughness of the composite material to improve the strength at the same time, is the researchers pursuing goal. Multi-element high-entropy alloy is a new alloy system, which have high hardness, high strength, wear resistance, corrosion resistance, high temperature thermal stability and special magnetic and electric properties, and many other excellent performance because of its unique microstructure. High entropy alloy and aluminum alloy matrix has a good interface wettability and interface compatibility because of natural interface binding properties between the metal to metal. If high entropy alloy is used as reinforcement to enhance the toughness of aluminum alloy, it will break through the bottleneck of traditional ceramics with enhanced toughness, the composite materials will increase the strength and plasticity at the same time. However, very little literature have been reported about high entropy alloy powders enhanced phase preparative high-toughness aluminum matrix composites. This paper mainly carried out on manufacturing high-entropy alloy and enhanced Aluminum Matrix Composites.First, we prepared representative four different component high-entropy alloy powder particles by mechanical alloying and study their behavior alloying, phase formation, powder size, morphology and phase of the law as well as process control agents composition. The results show that high entropy alloys of different compositions have a simple cubic structure. Through comparative analysis Al_0.25Cu_0.75FeNiCo powder prepared under different Manufacturing processes, we can get the conclusion that using the appropriate length of time dry milling and wet milling is the best. We can obtain a uniform particle size of the powder, and powder ratio is relatively high. By EDS analysis, we find that the longer the milling time, the introduction of impurities will be more. Considering powder particle morphology, size and extraction rates, the introduction of impurities and other factors, it is optimal milling Al_0.25Cu_0.75FeNiCo high entropy alloy under dry milling 16 h, and wet milling 24 h. By the same way（dry milling 16 h, and wet milling 24 h） processing three different composition high entropy alloys（Al0.5CuFeNiCoCr, AlCuFeNiCoCr, AlCuFeNiCoCrTi0.5）, particle morphology and size of the difference is not great. It showed that mechanical alloying process is the main factor affecting the high entropy alloy particle size and morphology, and high entropy alloy own characteristics associated with not great.Secondly, we prepared high entropy alloy particle reinforced 7075 aluminum matrix composites by powder hot extrusion, researched microstructure and mechanical properties of the aluminum matrix composites. Rod-shaped composite bar prepared get smooth surface, no cracking phenomenon, a more uniform distribution of composite particles, but a small number of crack reinforcement particles are present. EDS was found that the component of Al_0.25Cu_0.75FeNiCo high entropy alloy in composite before and after hot extrusion grains consistent, no large-scale element diffusion phenomenon occurred between the matrix and reinforced high entropy alloy. Composite elastic modulus, tensile strength are much larger than the base alloy.Thirdly, researching on volume fractions of high entropy alloy particles reinforced aluminum matrix composites found, with high entropy alloy particle content increases, an increase in the composite particle agglomeration region and increase the number of voids caused by the reunion, increased in size, resulting in reduced density. In mechanical properties, with the increase of the volume fraction, the composite elastic modulus and hardness increase, but the tensile strength and elongation after fracture first increase and then decrease trend. With the change in the particle volume fraction, fracture morphology of composites did not change significantly, indicating little effect on the volume fraction of the composite material of the type of fracture. The extrusion temperature was 400℃, extrusion ratio λ = 17.36, particle volume fraction of 5%, the composite elastic modulus, tensile strength and elongation after fracture was 79.9GPa, 437.6 MPa and 11.42 percent, far higher than 71.2GPa, 364.5 MPa and 8.36% of the base.Finally, we researched the different types of high entropy alloy particles reinforced aluminum matrix composites. The tissue distribution exhibits a similar regularity with the(Al_0.25Cu_0.75FeNiCo)p/7075 composite material. With the increase of volume fraction, particle agglomeration and rupture phenomena more serious, the attendant increase in the number of pores, reduce the density. Among the composite materials under the same conditions prepared,(Al_0.25Cu_0.75FeNiCo)p/7075 composite’s elastic modulus, tensile strength, elongation after fracture are the best, but the hardness of the different types of high entropy alloy particles reinforced aluminum matrix composites has little difference.