Research On Mechanical Properties And Hydrogen Embrittlement Mechanism Of Precipitate Strengthening Warm-Rolled Medium Manganese Steel

A precipitate strengthening warm-rolled medium manganese steel(Fe-0.01C-7Mn-2.5Ni-1.5Al)was designed in this work.The hierarchical multi-phase microstructure was achieved after warm-rolling and tempering treatment.It is found that this medium manganese steel has excellent hydrogen embrittlement resistance at high strength level.The evolution of the substructure of the samples was evaluated based on the microstructure characterization of the samples after warm-rolling and tempering,and the following results were drawn:1.The grain size and microstructure of medium manganese steel were controlled by warm rolling process,and the micro-internal substructure,nanoparticles and element partitioning were adjusted by additional tempering process.Tempered WRT samples not only show improved strength due to the precipitation strengthening of Ni Al phase(～ 87MPa),but also provide secondary work hardening under high strain stage due to the higher stable element content of austenite and fine and uniform grain size,which provides significant TRIP effect and increases the elongation.2.The hydrogen embrittlement sensitivity of WRT samples after tempering is significantly lower than that of WR samples before tempering.The main reason is that the austenite of WRT steel has a stronger capacity to capture hydrogen.At the same time,the Ni Al phase also plays a role in capturing hydrogen,but no precipitation was found in WR samples.In the condition of hydrogen charging,the refined austenite grains of WRT samples show excellent mechanical stability,thus delaying the diffusion of hydrogen.Therefore,the elongation of WRT samples is close to that without hydrogen charging,while the hydrogen brittle fracture occurs in the Luders zone of WR samples in advance.