A recrystallization heat-treatment to reduce deformation anisotropy of additively manufactured Inconel 718

Abstract

The aim of the current study is to investigate the suitability of a solutionizing recrystallization (RC) heat-treatment to improve the yield strength of laser powder-bed fusion (L-PBF) Inconel 718 (IN718), while decreasing deformation anisotropy under uniaxial compression. Scanning electron microscopy measurements show an increase in grain size, decrease in texture, and the formation of twins in the RC compared to the as-built (AB) and direct-age (DA) hardened conditions. Transmission electron microscopy measurements of the RC condition revealed the formation of nano-precipitates in the gamma matrix. As a result, the compressive stress-strain behavior showed an increase in the yield strength of the RC specimens compared to the AB condition in the quasi-static and high-strain rate regimes despite having significantly larger grain sizes. Post-mortem in-plane ellipticity measurements show a statistically significant decrease in the deformation anisotropy of the RC specimens compared to the AB and DA conditions. Overall, the solutionizing RC heat-treatment, when compared to the AB condition, resulted in an increase in yield strength and decrease in deformation anisotropy, two desirable outcomes necessary to continue to provide path-ways to transitioning L-PBF parts from the research laboratory setting to commercial implementation.

Keywords

• Inconel 718
• Microstructure
• Heat-treatment
• Laser powder bed fusion
• Split-Hopkinson pressure bar
• Compression