Study On Mechanical Behavior And Strengthening And Toughening Mechanism Of High Manganese High Aluminum Low Density Steel

Low-density high-strength and plastic steel not only has lower density than ordinary steel,but also has a combination of good strength and plasticity.It is considered to be the preferred structural material for reducing vehicle weight and improving crash resistance.Based on the study of the static tensile mechanical behavior of Fe-Mn-Al-C steels with three different aluminum contents?8wt.%¹2wt.%?and high manganese?28wt.%?at the earlier stage of the research group,the effect of temperature and Al content on its mechanical behavior and impact energy absorption ability under high-speed impact conditions are in depth analysised in this paper,and its mechanism of strengthening and toughening were clarified.Secondly,because the aluminum content is too high to affect the casting of the steel plate,consider replacing some of the aluminum in the steel with light element silicon,and adding nickel to the steel from the perspective of alloying,The Mn28Al8Si2Ni steel was fabricated in this paper,and the influence of different deformation conditions on its microstructure and mechanical behavior was discussed.The strengthening and toughening mechanism of Mn28Al8Si2Ni steel was revealed.The main conclusions are as follows:A high-speed impact test of Fe-Mn-Al-C high manganese high-alumina steel with a deformation rate of 5000s^-1 at different temperature?-50°C,23°C,75°C?was performed.The results show that with the increase of temperature,the stacking fault energy of steels increase gradually,the yield strength of Mn28Al12 and Mn28Al8 is greatly affected by temperature,while the yield strength of Mn28Al10 is less affected by temperature and has stable mechanical properties.When the deformation temperature is constant,the addition of aluminum increases the yield strength and decreases the strain hardening rate gradually.The experimental results show that Fe-Mn-Al-C high-manganese high aluminum steel has excellent impact energy absorption ability at-50°C⁷5°C.The mechanism of strengthening and toughening of Fe-Mn-Al-C high manganese high aluminum steels under high-speed impact condition was explored by OM,SEM,TEM and other analytical methods.The results show that the strain strengthening,strengthening of dislocations,grain boundary strengthening of the mechanical twins acted as a subgrain boundary,the refinement of the grains caused by the mutual obstruction between mechanical twins,and the softening of the material caused by the adiabatic effect under high-speed impact condition are the strengthening and toughening mechanism of Fe-Mn-Al-C high manganese high aluminum steels.At a constant strain rate,as the temperature increases,the yield strength and tensile strength of the Mn28Al8Si2Ni steel continuously decrease,and the elongation after fracture increases as a whole,but at the deformation rate 1×10^-3s^-1 or 1×10^-2s^-1,when the temperature increases from 100°C to 200°C,the elongation after fracture gradually decreases with increasing temperature.At a constant temperature,as the deformation rate increases,the yield strength increases and the tensile strength rises slightly as a whole,but at 23°C,the tensile strength decreases slightly,and the elongation after fracture increases first and then decreases.The strengthening and toughening mechanism of Mn28Al8Si2Ni steel was studied by SEM,TEM and other analytical methods.The results show that the strengthening of dislocations formed by the entanglement between the dislocations,the strengthening of the grain boundary caused by mechanical twins as a subgrain boundary,and the refinement of the grains caused by the mutual obstruction between mechanical twins are the main strengthening and toughening mechanisms.Simultaneously,through the microscopic observation of the deformed microstructure of the experimental steel,the influence of temperature and strain rate on its mechanical behavior was verified.