Effects Of Alloying Elements And Heat Treatment On Microstructures And Properties Of Fe₄Mn₄CoCr High Entropy Alloy

High-entropy alloy is a kind of metal material which is newly developed in recent years.High-entropy alloy usually consists of five or more kinds of alloy elements as the matrix,and several trace elements can be added on the basis of several principal element alloys.Different from traditional alloys,high entropy alloys tend to form single phase solid solution due to high entropy effect,and do not form intermetallic compounds.High entropy alloy has four effects:high entropy effect,hysteresis diffusion effect,lattice distortion effect and cocktail effect.Due to the four effects of high entropy alloy,the alloy has good mechanical properties,corrosion resistance,wear resistance,thermal stability and good magnetic properties,and is widely used in industrial production.As a result of Fe,Mn,Co,Cr,four elements in the periodic table of similar position,and have similar atomic radius and electronegativity,so this experiment adopts the Fe,Mn,Co,Cr,four elements,and then on the basis of these elements to add trace Ni,Al,Cu,using the vacuum arc smelting method to prepare the Fe4Mn4CoCr and Fe4Mn4CoCrNi0.2Al0.2,Fe4Mn4CoCrNi0.2Al0.2Cu0.2 high entropy alloys.After heat treatment at 800?,850?,900?and 950? for 2h,4h,6h,8h,12h,16h and 24h,the microstructure and crystal structure of the high-entropy alloy were analyzed with XRD and scanning electron microscope,the hardness change trend of the high-entropy alloy was analyzed with a durometer,and the saturation magnetic induction strength and coerce force of the high-entropy alloy were measured with VSM.(1)Fe4Mn4CoCr of as-cast high entropy alloys for dendritic structure,crystal structure of face-centered cubic structure.After heat treatment,dendrite tissue disappears,composition become more uniform,and in 900?× 8 h heat treatment after precipitation within the grain of layered organization,through the analysis,it is a discontinuous precipitation,the crystalline structure of the alloy after heat treatment is still face-centered cubic structure.The hardness of the alloy was increased from 122HV in the as-cast state to 404HV at 950? × 24h.The saturation magnetic induction strength of the alloy increases with the increase of heat treatment temperature and holding time.The coercivity of the alloy decreases with the increase of heat treatment temperature and holding time.(2)The as-cast Fe4Mn4CoCrNi0.2Al0.2 high entropy alloys for dendritic structure,crystal structure of face-centered cubic structure,contain some unknown phase at the same time.After heat treatment,dendrite tissue disappears,and began to gradually analysis within the grain grainy black in the second phase,it is a continuous precipitation.The unknown phase disappeared after heat treatment,the crystal structure into a face-centered cubic structure.The hardness of the alloy was increased from 116HV to 360HV.The saturation magnetic induction strength of the alloy increases with the increase of heat treatment temperature and holding time.The coercivity of the alloy decreases with the increase of heat treatment temperature and holding time.(3)The as-cast Fe4Mn4CoCrNi0.2Al0.2Cu0.2 high entropy alloys contains matrix structure and some small highlights,these little bright spots are the enrichment of Cu element but will find Cu element enrichment,the crystal structure of face-centered cubic structure,and contains some body centered cubic structure and unknown phase.After heat treatment,began to gradually analysis within the grain grainy black in the second phase,it is a continuous precipitation.The unknown phase disappeared after heat treatment,the crystal structure into a face-centered cubic structure.The hardness of the alloy is increased from 123HV to 373HV.The saturation magnetic induction strength of the alloy increases with the increase of heat treatment temperature and holding time.The coercivity of the alloy decreases with the increase of heat treatment temperature and holding time.