INFLUENCE OF THE GRADIENT ZONE EXTENT OF THE FUNCTIONAL GRADIENT PRODUCT OF THE CU/AL SYSTEM ON THE STRUCTURAL-PHASE STATE AND MECHANICAL PROPERTIES

Abstract

The formation of functional gradient Cu/Al materials with a continuous intermetallic surface layer by electron beam additive manufacturing is associated with the formation of a number of inhomogeneities and defects in the structure. The main obstacles to obtaining stable and defect-free FGM structures on the surface of the copper base are the difference in the coefficients of thermal expansion of copper and aluminum at the boundary with the formation of intermediates, cracks and delaminations. The formation of a smooth gradient from copper to intermetallic Cu/Al layers allows to avoid the formation of cracks and delaminations. In the work, defect-free functional gradient Cu/Al materials with different gradient zone widths were obtained using electron beam additive technology. The structural-phase state and mechanical properties of FGM Cu/Al over the entire height of the printed material are investigated. It is established that the Cu/Al gradient zone of FGM consists of the phases α-Cu, Cu4Al, Cu3Al and Cu9Al4. It is established that the width of the gradient zone affects the volume fraction of CuxAly intermetallic phases, which, in turn, determine the magnitude of the elongation at a constant value of the tensile strength (305 ± 10 MPa). The microhardness values increase sharply in the gradient zone and have an uneven distribution due to the formation of Cu4Al, Cu3Al and Cu9Al4 intermetallides. It is shown that the upper part of the Cu/Al FGM, consisting of 67 % Cu and 33 % Al (vol.), demonstrates a sharp drop in mechanical properties, which is probably due to the formation of the Cu9Al4 phase, the volume fraction of which prevails compared to other intermetallic phases of the CuxAly system.