二次热循环对晶内铁素体的影响

Effect of secondary thermal cycle on intragranular ferrite

采用物理模拟的方法研究了二次热循环对晶内铁素体的影响。用自动图像分析仪测量了夹杂物的大小、分布和密度 ,用透射电镜观察了晶内铁素体的形貌 ,并用能谱对诱导晶内铁素体形核的夹杂物进行了成分分析。研究结果表明 ,二次热循环对夹杂物的直径大小、分布和密度几乎没有影响。经过二次热循环过程后 ,诱导晶内铁素体形核、长大的夹杂物为MnO、TiO、SiO2 、Al2 O3 和MnS、CuS、(Mn ,Cu)S的复合物。 80 0～ 5 0 0℃的时间为 10s时 ,出现了晶内铁素体的感生形核。晶内铁素体的感生形核是由于一次晶内铁素体有较高的界面能和高密度的位错 ,两者共同促进晶内铁素体的感生形核。

The influence of secondary thermal cycle on intragranular ferrite was investigated by physical simulation method.The rule of non metallic inclusions distribution and the their sizes and density were mea sured with automatic image analyzer,and the chemical compositions and the figures of non metallic inclusions that inducted the formation nucleation of intragranular ferrite had been analyzed with transmission electron microscopy and X ray microanalysis.The results show that secondary thermal cycle has little effect on the chemical compositions,sizes and figures and density of non metallic inclusions that inducted the formation nucleation of intragranular ferrite.The non metallic inclusions beneficial to nucleation and growth of intragranular ferrite during secondary thermal cycle are oxidation products of Ti,Mn,Si,Al ,such as TiO,MnO,SiO 2,Al 2O 3 and the sulphides of Mn and Cu,such as MnS,CuS and(Mn,Cu)S.As the cooling time from 800 ℃ to 500 ℃ is 10 seconds,the sympathetic nucleation of intragranular ferrite are found.First intragranular ferrite has large boundary energy and high density dislocation during the cooling process.These two factors are the main driving forces to the sympathetic nucleation and growth of intragranular ferrite.