STUDY OF THE INFLUENCE OF THERMAL EFFECT ON THE STRUCTURE OF THE AlNiCoFeCr AND AlNiCoFeCrCu HEAT ELECTRICITY PRODUCED BY ARC MELTING

The phase composition and morphological features of the structure of high-entropy AlNiCoFeCr and AlNiCoFeCrCu alloys of equiatomic compositions obtained by arc melting, as well as the evolution of their structure after thermal action (up to 1650 °C) were studied using high-resolution electron microscopy and X-ray diffraction. The structure of the AlNiCoFeCr alloy after arc melting is a solid solution formed by grains of the B2 phase - 120 nm in size. The microhardness of the alloy is ~ 5000 MPa. When the alloy is heated to 1650 °C and then solidified at a rate of 1 deg/s, a structure of grains of the B2 phase ~ 50 µm in size with subgrains ~ 0.5 µm in size is formed. Two phases of different morphology and chemical composition are distinguished along the grain boundaries. The microhardness of the alloy decreases to ~ 4800 MPa. The structure of the AlNiCoFeCrCu alloy after arc melting is microcrystalline dendritic. The distribution of chemical elements throughout the alloy volume is non-uniform. Copper predominates in the dendrites. The interdendritic region has a Widmanstatten structure. Two types of structures are realized in the ingot: phases of the B2 type (in the matrix space) and phases of the A1 type (in the dendrites). The microhardness of the alloy is ~ 6500 MPa. When the alloy is heated to 1650°C, three endothermic processes occurring in the sample are recorded on the DTA thermogram. During subsequent solidification at a rate of 1 deg/s, a structure with two types of dendrites with a substructure is formed. The dendrites differ in size, shape and element content. The interdendritic space, as well as in the sample after arc melting, is represented by a Widmanstatten structure, but the dimensions of the plates are an order of magnitude higher. During crystallization, stratification occurs simultaneously in the dendrites and interdendritic space with the release of several phases of different composition and morphology. The microhardness of the alloy decreases to ~ 5000 MPa.