Effect Of TiC On Microstructure And Mechanical Properties Of Ductile Cast Iron

Ductile iron has good mechanical properties,casting properties,processability and price advantages,and has been widely used in various fields of the national economy,such as in automotive,construction,agriculture,machinery,energy,metallurgy,and military.According to statistics and forecasts,the production of ductile iron in the world will increase at a rate of 2%-4% per year.Conventional ductile iron has been unable to meet the production requirements and new requirements of economic development,so it is urgent to explore new ways to improve the structure and performance of ductile iron.TiC has high melting point,high hardness,high Young's modulus,high chemical stability and oxidation resistance,making it ideal for reinforcing steel materials.In cast steel,iron-based composite materials and white cast iron,the research on TiC ceramic particles has achieved certain results,but there is no relevant report in the field of as-cast ductile iron.Therefore,it is necessary to carry out the work of TiC on the effect of as-cast ductile iron.In this paper,the spheroidal graphite cast iron without adding alloy strengthening elements is used as the matrix.The influence of the addition mode and addition amount of TiC particles on its microstructure and mechanical properties is discussed.The strengthening law and mechanism of TiC particles on ductile cast iron are revealed.The main results are as follows:(1)The TiC particles are added to the ductile cast iron by direct addition,and the TiC is uniformly distributed in the matrix.When the addition amount of TiC is 0.020 wt.%,The spheroidization rate,the number of graphite,the area ratio of graphite and the ferrite content in the structure of ductile iron are greatly improved,and the ferrite and pearlite grains are refined,so that the strength of the ductile iron is not lowered.Next,improve plasticity and toughness.When the addition amount of TiC particles is gradually increased,the spheroidization rate and the number of graphite are basically unchanged,and the pearlite content is gradually increased,so that the strength and hardness of the ductile cast iron are improved,and the ductility and toughness are gradually decreased.(2)Adding 0.041 wt.% of TiC particles by means of an intermediate alloy,the spheroidization rate and the number of graphite of the ductile iron are significantly increased,the ferrite content is slightly decreased,and the ferrite and pearlite grains are refined.The ductility,toughness and strength of ductile iron are simultaneously increased.(3)The effect of endogenous TiC particles and content on as-cast ductile iron was studied by reactive casting method.TiC particles are unevenly distributed with austenite dendrites in the matrix.When the content of endogenous TiC particles is 0.021 wt.%,the spheroidization rate,the number of graphite per unit area and the ratio of precipitated graphite increase,the plasticity of ductile iron increases the most,and the comprehensive mechanical properties are the best.When the content of TiC particles is between 0.060 wt.% and 0.083 wt.%,the spherical aberration,the number of graphite and the area ratio of graphite are reduced,and the pearlite content is increased.At this time,the tensile strength of the ductile iron is the highest,and the plasticity is Reduced.When the content of TiC reaches 0.161 wt.%,ductile iron has the highest hardness and yield strength,and the lowest elongation.(4)Comparison of the effects of adding and endogenous TiC particles on ductile iron: The effect of adding TiC particles to improve graphite is significant,while the effect of endogenous TiC particles on matrix structure is significant.From the distribution point of view,the distribution of TiC particles in ductile cast iron is more uniform,while the endogenous TiC particles are unevenly distributed with austenite dendrites.From the effect point of view,the addition of TiC particles enhances the plastic toughness effect of ductile iron,and the endogenous TiC particles mainly enhance the strength of ductile iron.Regardless of the addition method,when the TiC content is about 0.02 wt.%,the overall performance of the ductile iron is improved.