Effect Of Ni Content On Strengthening And Toughening Mechanism Of Cu-bearing Aging Steel

In this paper,the microstructure of Cu-bearing aging steel with different Ni contents were treated by quenching after 1h of solid solution at 900? and air cooling tempering at 550? after1 h of solid solution at 900? for 2h,and the effects of different Ni contents on mechanical properties of cu-bearing aged steel were analyzed.The results show that:The microstructure of Cu-bearing aging steel after quenching is contist of martensite and granular bainite.With the increase of Ni content,the hardenability of Cu-bearing aging steel is improved,and the martensite volume fraction in the quenched state increases accordingly.Ni element can effectively improve the microhardness of Cu-bearing aging steel.When the Ni content increases from 0.99% to 3.47%,the microhardness of quenched Cu-bearing aging steel increases from 288.2HV to 332.8HV.The microhardness of tempered state increased from254.7HV to 303.6HV.When the Ni element content increased from 0.99% to 3.47,the yield strength of Cu-bearing aging steel increased from 863.4MPa to 915.9MPa,and the elongation after fracture decreased from 18.0% to 16.0%.The fine structure of Cu-bearing aging steel was observed,and the results showed that: with the increase of Ni element content,the effective lath size of quenched decreased from 2.1?m to1.9?m.The effectiv lath size of tempered decreased from 2.9?m to 2.4?m.Observed by transmission electron microscope,the width of quenched lath decreased from 0.272?m to0.239?m.The effective grain size in Cu-bearing aging steel becomes smaller,which provides good hardness,plasticity and ability of arresting.MATLAB was used to reconstruct the prior austenite of EBSD data,and the prior austenite image size orientation reconstruction based on the relationship between martensite and the prior austenite is counted.When the Ni content was 0.99%,1.97%,2.48% and 3.47%,the prior austenite grain size in the quenched state was 23.2 ?m,23.6?m,26.5?m and 30.6?m.With the increase of Ni content,the prior austenite grain size in Cu-bearing aging steel grew slightly after being insulated at 900? for 1h.