Dynamic Mechanical Properties and Strengthening Mechanism of Co-Free Maraging Steel Manufactured by Arc Additive Manufacturing

Abstract

The novel Co-free maraging steel (MS) thin wall was manufactured by wire-arc additive manufacturing (WAAM). The microstructure of WAAM-MS was characterized by XRD, SEM, TEM and EBSD. The quasi-static and dynamic mechanical properties were investigated by tensile tests and Split Hopkinson Pressure Bar (SHPB). The microstructure of WAAM-MS mainly includes martensite and austenite, and a large number of dislocation lines and Ni3Ti second phase uniformly distributed in the grains. The strengthening mechanisms of WAAM-MS are mainly dislocation strengthening and second phase strengthening, which contribute 297 MPa and 295 MPa respectively. The deformation mechanism of WAAM-MS under low strain rate (488s-1) is mainly dislocation slip, while after the strain rate reaches 1372s-1, the deformation mechanism is deformation twinning and dynamic recrystallization (DRX). When the strain rate reached 2083s-1, deformation twinning is still the main deformation mechanism, and dynamic recrystallization is intensified. The J-C constitutive model of WAAM-MS was adjusted, and the predicted results were consistent with the experimental results. This study provided important theoretical basis for the application of Co-free martensitic aging steel manufactured by arc additive manufacturing in dynamic load impact environments.

Keywords: Co-free maraging steel, Wire-arc additive manufacture, Dynamic compression, Strengthening mechanism, deformation mechanism