In-situ residual stress reduction, martensitic decomposition and mechanical properties enhancement through high temperature powder bed pre-heating of Selective Laser Melted Ti6Al4V

By H. Ali, Le Ma, H. Ghadbeigi, K. Mumtaz. 2017

356 citations recorded by the source corpus.

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. Post-process heat treatments can be applied to SLM components to remove in-built residual stress and improve ductility. The use of high temperature pre-heating during an SLM build can assist in reducing thermal gradients, enable a more controlled cooling with the possibility to control/tailor as-built mechanical properties. In this work a high temperature SLM powder bed capable of pre-heating to 800 °C is used during processing of Ti6Al4V feedstock. The effect of powder bed temperature on residual stress formation, microstructure and mechanical properties was investigated. It was found that increasing the bed temperature to 570 °C significantly reduced residual stress formation within components and enhanced yield strength and ductility. This pre-heating temperature enabled the decomposition of α ′ martensitic microstructure into an equilibrium α+β microstructure. At 570 °C the yield strength and elongation of components was improved by 3.2% and 66.2% respectively.

Subfields: Automotive Engineering, Mechanical Engineering

View Paper: https://www.semanticscholar.org/paper/16dd9f14ae2c40c1c0b2c2451cac30f55e3be3da

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In Automotive Engineering

1. D. Agius
2. Chao-lin Tan
3. K. Kourousis
4. C. Wallbrink

In Mechanical Engineering

1. D. Agius
2. Chao-lin Tan
3. K. Kourousis
4. C. Wallbrink

Citations in the corpus

• A review of the as-built SLM Ti-6Al-4V mechanical properties towards achieving fatigue resistant designs (2018, background): “[18], in an investigation of the effects of powder bed preheating, which highlighted the significant influence of the powder bed temperature on the SLM Ti-6Al-4V microstructure formation.”
• Recent innovations in laser additive manufacturing of titanium alloys (2024, background): “For α -Ti and ( α + β )- Ti alloys, the substrate preheating can also promote in-situ martensite decomposition, thereby improving the ductility and fatigue performance [143, 144].”