Structure, crystallographic texture and anisotropy of properties of VZh159 alloy and how they are influenced by regimes of selective laser melting and final heat treatment

Abstract

This paper examines the effect of scanning strategy (unidirectional scan, island scan and a scan with a 60о turn of the laser beam between layers) during selective laser melting and heat treatment on the crystallographic texture and mechanical properties of VZh159 alloy specimens. Application of different scanning strategies leads to two types of crystallographic texture formed in specimens: the axial component <100> gets reinforced in the unidirectional strategy, while it is the texture component {100}<001> in the other cases. After printing, the specimens were subjected to different regimes of heat treatment. They included quenching from 1,100 oC; quenching from 1,100 oC and ageing at 800 and 700 oC; quenching from 1,100 oC and ageing at 900, 800, 700 and 650 oC. When heat treatment (ageing) tests are conducted at room temperature, it leads to increased yield point and strength as a result of secondary phase precipitation at grain boundary and in grain core, while plasticity drops. During high temperature tests, no strength gain was found after heat treatment. In all heat treatment regimes, the authors observed anisotropy of mechanical properties in the specimens caused by the crystallographic texture that remains after heat treatment. The maximum strength and yield point were detected at 45о load application to growth direction during printing. At the same time, the anisotropy of yield point does not change during high temperature mechanical testing (at 850 oC) and has no dependence on the amount of additional precipitates. It suggests that crystallographic texture plays a defining role for anisotropy of properties.The research was conducted under financial support of Russian Federation presented by the RF Ministry of Science and Higher Education (Agreement No. 075-15-2021-1352).