4:45 PM - MS04.08.08
Microstructure and Mechanical Properties of AlCoCuFeNi0.8 High Entropy Alloys
Northwestern Polytechnical University1
Compared with traditional alloys, high entropy alloys have excellent properties such as simple phase composition, higher strength, higher hardness, better wear resistance, better corrosion resistance, and unique electromagnetism as a novel alloy. In this work, Effects of Al and Cu content on the microstructure and properties in AlxCoCu1-xFeNi0.8 alloys were investigated by XRD, SEM, EDS, TEM, microhardness testing, tensile and compression testing. In AlxCoCu1-xFeNi0.8 (x=0.25, 0.3, 0.4, 0.5, 0.75) high-entropy alloys, the phase composition of alloys gradually changes from a single face-centered cubic (FCC) structure to a body centered cubic(BCC) structure and a little amount of FCC structure with the increase of Al content and the decrease of Cu content. Microstructure of the as-cast AlxCoCu1-xFeNi0.8 (x=0.25, 0.3, 0.4, 0.5)alloys presents the typical dendritic morphology, and microstructure of as-cast Al0.75CoCu0.25FeNi0.8alloy presents the cellular crystal structure and the dendritic morphology. EDS results show that Cu element tends to be segregated in the inter-dendrites. Al0.75CoCu0.25FeNi0.8alloyhas the best comprehensive mechanical properties. The compressive yield strength and compressive strength are 1585MPa and 2049MPa, respectively. The fracture strain is 16.4%, and the hardness is 619.4Hv.The heat treatmentsof AlxCoCu1-xFeNi0.8 (x=0.25, 0.3, 0.4, 0.5, 0.75) alloys at 8000C for 0.5h, 6h, 12h were investigated, too. The inter-dendritic phase was obtained by eutectic reaction and grain boundary generated spinodal decomposition after heat treatment, forming a net structure. After 0.5h of heat treatment, the nano-sized precipitate phase is generated. With the increasing of heat treatment time, the nano-meter precipitate phase is dissolved, and the spinodal decomposition occurs in Al0.25CoCu0.75FeNi0.8alloy. The highest yield strength is obtained at 0.5h heat treatment. and BCC phase is still the main phase of Al0.75CoCu0.25FeNi0.8 alloy. After heat treatment for 6h, the yield strength of Al0.75CoCu0.25FeNi0.8 alloy is as high as 1719MPa.