Tensile yield behavior of high strength-ductility 24CrNiMoY alloy steel by dual-field assisted laser direct energy deposition

Abstract

Laser direct energy deposition (LDED) high strength-ductility matching alloy steel is promising for the manufacturing of anti-deformation and deformation parts. However, there are differences in strength-ductility matching and tensile yield behavior of parts with different deformation requirements. It is essential to understand how to control the microstructure and prepare alloy steel with either continuous or discontinuous yield phenomena to meet manufacturing requirements of the deformation or anti-deformation parts. To address this issue, the microstructure evolution and tensile yield behavior of 24CrNiMoY alloy steel deposited by preheating-ultrasonic dual-field assisted LDED using a multi-factor optimized-design response surface method combined with the experiment is investigated. The experimental results indicate that the relationship between microstructure evolution and strength-ductility of alloy steel prepared by dual-field-assisted LDED was clarified. Interestingly, we found that the various dual-field synergistic parameters help to prepare tensile samples with either continuous or discontinuous yield behavior to meet the requirements applicable to the alloy steel parts with different working conditions. It is discovered that the characteristics of bainite and ferrite, including their quantity, distribution, and morphology, can influence the continuous or discontinuous tensile yield behavior of alloy steel. The advanced technology enabled the preparation of high strength-ductility 24CrNiMoY alloy steel with tensile strength up to 1060 MPa, elongation up to 13.8%, and a strength-plastic product up to 14.6 GPa%. This work breakthrough has overcome the technical bottleneck associated with the strength-ductility trade-off of LDED alloy steel, which makes it possible to directly obtain continuous or discontinuous yield behavior through process control. This study provides a useful theoretical and technical guideline for LDED preparation of high strength-ductility alloy steel parts meeting anti-deformation or deformation requirements.