钢中磷化物的相价电子结构及其对冷脆的影响

非金属元素P在晶界偏析且能引起冷脆的研究很多,但在电子结构层次上P偏析及引起冷脆的原因尚不十分清楚。基于"固体与分子经验电子理论(EET)",建立Fe3P的相空间电子结构计算模型,计算γ-Fe-P、Fe3P和稀土磷化物(REP)的价电子结构,并利用相结构因子nA分析非金属元素P偏析及引起冷脆的原因。计算结果分析认为,nA较小的γ-Fe-P相结构单元首先在晶界处偏析,当磷偏析浓度达到较高时,nA较大的Fe3P才在晶界处析出,引起冷脆现象;因REP的nA比γ-Fe-P的nA小,稀土元素加入后,稀土元素比Fe先扑捉到P元素形成稀土磷化物,从而改善磷的偏析并消除Fe3P引起的冷脆。

Effect of the valence electron structures of phosphide on cold short in steel

Although the researches on the grain boundary segregation and the cold short of non-metallic element of phosphorus are extensive,the reasons why the phosphorus element can generate the grain boundary segregation and the cold short are not clear on electron structural level.Therefore,based on the empirical electron theory of solid and molecule(EET),the calculation model of valence electron structures of Fe3P is established,the valence electron structures of γ-Fe-P,Fe3P and rare compound(REP) are calculated,and the reasons why the phosphorus element can generate the grain boundary segregation and the cold short are explained with the phase structure factor nA.The analysis of calculated results shows that the phase structure unit of γ-Fe-P with smaller nA firstly segregates on grain boundary,then the Fe3P with larger nA precipitates on grain boundary and generates cold short when the segregating concentration of phosphorus is high enough.The rare-earth elements easily form rare compound with phosphorus than Fe element because the nA of REP is smaller than that of γ-Fe-P,so the grain boundary segregation of phosphorus is improved and the cold short of Fe3P is also removed.