Abstract
During the Selective Laser Melting (SLM) process large temperature gradients can form, generating a mismatch in elastic deformation that can lead to high levels of residual stress within the additively manufactured metallic structure. Rapid melt pool solidification causes SLM processed Ti6Al4V to form a martensitic microstructure with a ductility generally lower than a hot working equivalent. Currently post-process heat treatments can be applied to SLM components to remove in-built residual stress and improve ductility.This study examined the effect of scanning strategy (scan vector lengths and scan vector rotation) and rescanning strategy on residual stress formation and mechanical properties of SLM Ti6Al4V parts. 90° alternating scanning strategy resulted in the lowest residual stress build-up for SLM Ti6Al4V parts built on both the standard and modified Renishaw platforms using a modulated Nd-YAG fiber laser. Scanning strategy did not show any direct correlation with mechanical properties. Re-scanning with 150% energy density resulted in 33.6% reduction in residual stress but the effect on mechanical properties was detrimental and samples failed prematurely. The study was based on detailed experimental analysis along with Finite Element simulation of the process using ABAQUS to understand the underlying physics of the process.
Highlights
Additive Manufacturing (AM) techniques are of interest to industry due to capability of manufacturing fully functional complex geometries from a digital model by joining material in a layer by layer manner [1,2]
A significant problem associated with Selective Laser Melting (SLM) components is the development of high internal residual stress [3]
These high cooling rates and large temperature gradients result in high residual stress build up in the SLM components
Summary
Additive Manufacturing (AM) techniques are of interest to industry due to capability of manufacturing fully functional complex geometries from a digital model by joining material in a layer by layer manner [1,2]. This study investigated the effect of scanning strategy on residual stress and mechanical properties of SLM Ti6Al4V components. Insight from FEA simulation combined with experiments can lead to a better understanding of the process This is first of its kind comprehensive study on the effect of laser scanning and re-scanning strategies on residual stress build up and mechanical properties of SLM Ti6Al4V parts. This work studies the effect of scanning strategy (Scan vector length and rotation) on residual stress and mechanical properties. FEA simulation is used in combination with experimental trials to understand the underlying phenomena associated with the residual stress build up and trend in mechanical properties of SLM Ti6Al4V samples.
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