| The microstructures and mechanical properties of three kinds of medium manganese low density steels in Fe-8.3Mn-(9.5Al,12 Al,14.5)Al-C series were studied in this paper.In order to provide references for revealing the mechanism of hydrogen embrittlement in medium manganese low density steels,the electrochemical hydrogen charging and slow strain rate tensile tests and the ABAQUS finite element simulation were combined to studies the hydrogen embrittlement characteristics of two experimental steels,9.5Al and12 Al.In this paper,the phase diagram of medium manganese low density steels in Fe-8.3Mn-(9.5Al,12 Al,14.5)Al-C series was calculated using Thermo-Calc software,and the main components,the proportions of different phases and the formation temperature were analyzed.The melting point,peritectic reaction and eutectoid reaction temperature of Fe-8.3Mn-xAl-1C series medium manganese low density steel were observed with the Al content.The hot rolled microstructures of three kinds of low density steels(9.5%,12%,and 14.5%)were studied by means of OM,SEM,and XRD.It is found that the morphology of ferrite and austenite phases in steel changes with the change of Al content.At 9.5Al,austenite is distributed in a network on the ferrite matrix,and in 12 Al and 14.5Al steel,ferrite and austenite are parallel.In the rolling direction was a strip-shaped interval distribution.For the mechanical properties of the three experimental steels,it was found that the 9.5Al steel has higher strength and good plasticity;the strength of the 12.5Al steel is higher,but the plasticity decreases;the strength and plasticity of the 14.5Al steel are both poor.Using ABAQUS finite element software to simulate hydrogen concentration changes in steel under different conditions,the effects of different external hydrogen concentration environments on the diffusion behavior of hydrogen in steel were simulated.At the same time,the influence of second phase in steel on the diffusion of hydrogen in steel was studied.The influence of the orientation of the second phase on the hydrogen concentration at different positions and times in the steel was analyzed.It is found that the hydrogen concentration in the sample increases with the increase of the hydrogen concentration in the sample,but the hydrogen concentration changes at different locationsare different.The second phase have an adsorption-inducing effect on the hydrogen atoms in the steel matrix and affect the distribution of hydrogen in the steel.The effect of hydrogen charging time and current density on the hydrogen content in9.5Al and 12 Al low-density steels was investigated using electrochemical hydrogen charging experiments.The combination of slow strain rate tensile test and fracture analysis showed that both experimental steels produced significant plastic loss after hydrogen charging.The embrittlement index of 9.5Al experimental steel was lower than that of 12 Al experimental steel,and 12 Al steel exhibited higher hydrogen embrittlement sensibility.The analysis shows that the 12 Al experimental steel has higher strength,and the higher Al content results in a relatively lower austenite content.At the same time,the fine grains in the steel promote the enrichment of hydrogen in the steel,resulting in higher hydrogen embrittlement sensitivity. |
PDF Full Text Request