Abstract
An as-cast macrostructure of electron beam additively manufactured metallic materials was represented by coarse columnar grains whose axes were inclined at 25° with respect to the substrate’s plane. One part of the as-grown samples was annealed to form a coarse grain microstructure while the other part was pre-deformed by forging and then annealed what allowed obtaining recrystallized microstructures with small grains and multiple annealing twin boundaries. This sample showed both high strength and plasticity during the tensile tests. These tensile tests demonstrated also two-stage stress-strain curves as depended on their strain hardening rates. High and low strain hardening rates corresponded to a twinning-dominated deformation at stage II and dislocation-base deformation at stage III. A submicron size strain-induced grain-subgrain microstructure was formed in the vicinity of a necked zone as a result of combined twinning/dislocation grain refining.
Highlights
Additive processes have been developed during recent last decades to allow the manufacturing of complex near net-shape articles with their mechanical characteristics suitable for further mechanical processing
An as-grown single-phase bronze sample is microstructurally characterized by columnar grains oriented at some angle with respect to the wall growth direction, and whose lengths increase with the wall height to be as great as ~10 mm (Figure 3)
Directional solidification of metal in the course of additive electron beam wire-feed manufacturing resulted in growing coarse columnar grains in low stacking fault energy aluminum bronze samples
Summary
Additive processes have been developed during recent last decades to allow the manufacturing of complex near net-shape articles with their mechanical characteristics suitable for further mechanical processing. There are, some problems with improving the quality of macro-and microstructures in the layer-by-layer grown materials and obtaining the desired optimal structures and phases It is a well-known fact that electron beam additive manufacturing (EBAM). On specific metallic materials like titanium [1,2] or aluminum bronze [3] might result in growing large columnar dendrites whose height would be almost equal to that of the obtained sample. Such a sample would be characterized by high anisotropy of its mechanical characteristics, and to improve the situation, either heat or thermo-mechanical treatment must be used. There are many fewer methods in use for low stacking fault energy single-phase aluminum bronzes printed using the electron beam wire-feed
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