Stress-induced martensitic transformation mechanism in the crack behaviour of compressed additively manufactured Ti-5553 alloy: A variant selection approach

Abstract

This investigation aims to explore the unresolved crack formation mechanism in compression, based on the influence of the crystallographic nature in the Ti-5553 alloy, which is susceptible to Laser Powder Bed Fusion (PBF-LB) defects as well as stress-induced martensitic transformations (SIMT). The cylindrical samples were obtained and subsequently subjected to a compressive load to investigate the BCC/orthorhombic transformation in the failure behaviour. Here, the variant selection approach based on the Schmid factor (SF) criteria was employed to elucidate the martensitic phase transformations and their role in the crack path. It was demonstrated that the accumulation of plastic strain at discontinuities that result from the processing route initiate the martensitic transformation. Additionally, a stacking fault in the orthorhombic phase will assist the α’’/α’ (Orthorhombic/Hexagonal closed packed - HCP) transformation. The analysis showed that the SIMT mechanism follows the ${\left\{101\right\}}_{\beta }$//${\left\{001\right\}}_{\alpha \prime \prime }$//${\left\{0001\right\}}_{\alpha \prime }$ and ${<111>}_{\beta }$//${<110>}_{\alpha \prime \prime }$//${<11\bar{2}0>}_{\alpha \prime }$ orientation relationship and that the failure on the transverse direction follows a direction close to ${<212>}_{\beta }$ // ${<211>}_{\alpha \prime \prime }$//TD.