Si对蠕墨铸铁金属基体合金微观组织及导热的影响

Effect of Si on Microstructure and Thermal Conductivity of Vermicular Cast Iron Matrix Alloys

通过对已有缸盖本体进行EDS能谱分析和相图模拟,得到蠕墨铸铁的金属基体成分Fe-x Si-0.6C-0.1Mn-0.05V(x=1.2、1.5、1.8、2.1wt%)。采用真空电弧熔炼制备该基体合金,并进行930℃保温2 h随炉冷却处理。使用XRD、光学显微镜(OM)和扫描电镜(SEM)对基体合金的微观组织进行分析和表征,通过激光导热仪(TA)测量了不同温度下的热扩散系数,研究Si对蠕墨铸铁基体导热性能的影响。结果表明:蠕墨铸铁金属基体合金为珠光体和铁素体,随着Si含量升高,珠光体的含量逐渐降低,晶格畸变程度先加剧后减缓,热扩散系数和导热系数先降低后升高,比热容变化不明显。Si含量为1.8%时,基体合金的晶格畸变程度最严重,热扩散系数最低,导热系数越低。随着温度的升高,热扩散系数降低,比热容升高,导热系数增大,不同Si含量基体合金的热扩散系数差异减小。

The composition of the vermicular cast iron metal matrix was obtained by EDS of the existing cylinder head and phase diagram simulation,which was Fe-x Si-0.6C-0.1Mn-0.05V(x=1.2,1.5,1.8,2.1wt%).The matrix alloys were prepared by vacuum arc melting,and then the treatment of the alloys heated at 930℃ for 2 h then cooled in furnace was carried out.The microstructure of the matrix alloys was analyzed and characterized by using XRD,optical microscopy(OM)and SEM.The thermal diffusion coefficients at different temperatures were measured by laser thermal conductivity(TA) to study the effect of Si on the thermal conductivity of the vermicular cast iron matrix.The results show that the metal matrix alloy of the vermicular cast iron is pearlite and ferrite.With the increase of Si content,the content of pearlite decreases gradually,the lattice distortion degree first intensifies and then eases,the thermal diffusion coefficient and thermal conductivity decrease first and then increase,the change of the specific heat capacity is small.When the Si content is 1.8%,the lattice distortion degree is the most severe,the thermal diffusion coefficient and the thermal conductivity are the minimum.With the increase of the temperature,the thermal diffusion coefficient decreases,the specific heat capacity increases,and the thermal conductivity increases,the difference of the matrix alloys with different Si contents decreases.