Study On Microstructure And Properties Of High-Aluminum High-Carbon Steel

Adding a lot of lightweight elements such as Al in steels can effectively reduce the density,and enhance the resistance against to high temperature oxidation and corrosion,while this causes the brittleness at room temperature,and thus limits their application.In the present work,lightweight steel Fe–1.86Mn-6.98Al-0.82C with density of 6.98 g/cm²was used.By solution and aging,the different fractions of martensite and different sizes of?carbides were obtained in microstructure,after that,we measured the mechanical properties and corrosion resistance of different sample of the organization,thus the intrinsic relationship between microstructure and properties are given.Thermal-Calc software was used to examine the phase diagram of the steel.combining with the dilatation curve and the microstructure observation of the solid solution treatment samples,it is shown that the balance microstructure at room temperature of the steel is?+?,phase transition point Ac₁ is?920?,and no complete austenitizing phase region exists.Solid solution treatment at 950?,austenite with grain size of?10 microns,and fraction of?40%was obtained.Increasing the solution temperature resulted in the size of austenitic grains,and the decrease in the fraction of austenite.Very poor room-temperature plasticity was found in the samples processed by different aging treatments after solution at 950?.The highest yield strength?1089 MPa?and tensile strength?1107 MPa?was obtained in the sample processed by aging at 600?for 2 h after solution at 950?.This is mainly attributed to that the nanoscale?carbides precipitated in the ferrite during aging at 600?.When the aging time is too long,the?carbides grow up,and hence increasing the brittleness and reducing the strength.The measurements of high temperature tensile strength and oxidation resistance of the test steel show that the test steel has good high temperature performance,and the tensile strength at 600?is 350 MPa,and the reduction coefficient is 0.33 compared with that of room temperature.During heating up to 1100?,the oxidization induced weight increment 1/3 of 1Cr18Ni9Ti austenitic stainless steel and 1/40 of the plain carbon steel T8.From the polarization curves of samples with different microstructures in different periods of electrochemical corrosion test,it can be found that the best corrosion resistance occurred in 950?solution sample,which has the wdider corrosion passivation range than other samples.