Analysis on microstructure and mechanical properties of 960 MPa deposited metal

The solid wire of high strength and toughness was successfully developed by vacuum melting technique. The microstructure and mechanical properties of deposited metal were analyzed in detail by means of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), instrumented impact tests. Results showed that the highest tensile strength and toughness of deposited metal can reached to 920 MPa and 66.7 J (-60 ℃), respectively, for the alloying systems of Mn-Ni-Cr-Mo-Ti. With the content of alloying elements being increased, the microstructure transformed from bainite to the mixture of granular bainite and low carbon martensite. However, the higher content of alloying elements in deposited metal can promote the formation of martensite, and its appearance is adverse to toughness. The existence of the film-like residual austenite which can improve the impact toughness was found between the lath-like bainite ferrites.