Effect of Heat Treatment on Fracture Behavior of AISI 630 Alloy Manufactured by Directed Energy Deposition

Abstract

AISI 630 alloy is widely used in the manufacture of CFM56 series aeroengine fan casing because of its high strength and excellent ductility. Herein, AISI 630 alloy is directly manufactured by directed energy deposition. The microstructural evolution, mechanical properties, and fracture behavior of AISI 630 alloy in as‐deposition, solution, and aging conditions are analyzed. Scanning electron microscopy, X‐ray diffraction, and electron backscattering diffraction are used to characterize the microstructure and phase characteristics. Mechanical tensile and Vickers hardness tests are performed. The results show that the samples as‐deposited, solution, and solution and aging samples are all composed of α phase and small amount γ phase, where γ phase proportions are 10.6%, 0.2%, and 10.8%, respectively. Due to transformation‐induced plasticity effect, the as‐deposited specimens have the highest strain hardening coefficient (0.410–0.432), which results in the tensile strength of 1121–1143 MPa, the yield strength of 279–293 MPa, and the fracture elongation of 14.9%. After solution and aging treatment, the tensile strength is increased by about 8% (1206–1239 MPa), the elongation at break is decreased by about 30% (9.6–11.4%), and the yield strength is increased by more than one time (740–907 MPa).