Study of the Structure and Mechanical Properties of Aluminum Bronze Printed by Electron Beam Additive Manufacturing

Abstract

Introduction. The development of additive manufacturing technologies expands the possibilities of manufacturing (printing) products using a variety of materials. The printing process is carried out by local high-energy heating of the filament and substrate, due to which a molten bath is formed. Under such conditions, the formation of the structure of the material occurs under conditions of rapid crystallization and repeated cyclic heating. An important problem in printing bulk products from most structural alloys is the formation of a dendritic structure. The shape and size of dendrites, as well as the formation of secondary phases associated with it, can affect the strength and performance of products. The purpose of the work is to study the structure and mechanical properties of aluminum bronze obtained by the method of electron beam additive production. In this work, the features of the formation of the structure of aluminum bronze depending on the area of the sample are studied. Mechanical tests are carried out under static tension and compression of samples cut in longitudinal and cross sections relative to the direction of printing. The methods of investigation are mechanical tests for compression and tension, optical metallography, scanning electron microscopy. Results and discussion. Based on the analysis of metallographic images, four characteristic types of microstructures are formed at different heights from the substrate in the printed material. The first type is small dendritic grains with intermetallic particles. The second is small dendritic grains. The third is large columnar dendritic grains. Fourth are wide dendritic grains with small inclusions of the secondary phase. The formation of these types of microstructures is due, firstly, to the use of a steel substrate, and secondly, to a change in heat removal conditions as the height of the sample increases during printing. Based on the tests, a significant anisotropy of the mechanical properties was revealed, which is due to the directed nature of the growth of columnar dendritic grains, as well as a change in grain size along the height of the printed material. The obtained results expand the fundamental ideas about the processes of structure formation of alloys in the conditions of electron-beam additive production and can be used in developing technologies for printing products made of copper alloys.