| Ductile iron,as a special engineering material,has great mechanical properties,casting properties and relatively low cost.It has been widely used in many fields such as wind power generation and automobile industry.In recent years,the use of ductile cast iron has been increasing year by year,and people have put forward requirements for all aspects of performance of nodular cast iron under operating conditions.Traditional nodular cast iron no longer meets the development needs of various industrial fields.Therefore,new ways and methods to improve the performance of ductile iron need to be continuously explored.In recent years,the research on ceramic particle-reinforced metal matrix composites has been increasing,which can be used as an effective way to improve the performance of materials.ZrO2 has high hardness,melting point and excellent chemical stability.According to theoretical calculations,the mismatch ? between ZrO2 and y-Fe is 0.77%,and the characteristic parameter "?p"of empirical electron theory is 1.475.It can be seen that ZrO2 can be used as a base phase to promote the heterogeneity of primary y-Fe It can be seen that ZrO2 can be used as the basis for the heterogeneous nucleation of primary y-Fe.In this paper,the high-energy ball milling method is used to pre-disperse ZrO2 particles.Through the improved design of the ZrO2 addition method,the mechanical stirring process is determined to be the optimal addition method for ZrO2,and ZrO2 is introduced into the ductile iron melt through this process,and nano-ZrO2 particles are added.The amounts are 0.25wt.%,0.5wt.%,0.75wt.%and 1wt.%,respectively.The results of the study showed that the microstructure of ductile iron was improved to varying degrees with different additions of nano-ZrO2 particles.As the addition of ZrO2 increased,the spheroidization rate and roundness of graphite spheres increased,and the number of graphite per unit area increased.The average size is reduced,and the ferrite grains in the matrix structure are obviously refined.When the addition amount of ZrO2 is 0.75wt.%,the refining effect of ferrite grains and graphite structure is the most obvious,and the number of grains per unit area is the largest.The pearlite structure is refined to different degrees.With the increase of the amount of ZrO2 added,the pearlite lamella spacing gradually decreases.With different contents of ZrO2,the room temperature tensile properties of ductile cast iron samples have improved to varying degrees.The tensile strength and yield strength of ductile cast iron increase with the increase of ZrO2 content,and the elongation presents a trend of first increasing and then decreasing.Nodular cast iron with 0.75wt.%ZrO2 has the best tensile properties,the tensile strength can reach 438.6MPa,which is 60.6MPa higher than the sample without ZrO2,and the elongation is 22.4%,which is higher than that without ZrO2.The sample increased by 7.5%;with the increase in the amount of ZrO2,the impact absorption energy of ductile iron showed a trend of first increasing and then decreasing.The impact absorption energy of the sample with 0.75wt.%ZrO2 was 17.3J,which is different from that of nodular cast iron.Compared with the sample with ZrO2 added,the friction and wear properties of ductile iron with different contents of ZrO2 are also improved.The friction and wear properties of spheroidal graphite iron with different contents of ZrO2 are also improved.The average weight loss of the wear samples were 0.0828g,0.0723g,0.0610g,0.0456g,and 0.0504g,respectively.When the ZrO2 addition amount was 0.75wt.%,ductile iron had the best wear resistance. |
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