(1. 湖南大學(xué) 汽車車身先進設(shè)計制造國家重點實驗室，長沙410082;
2. 湖南大學(xué) 材料科學(xué)與工程學(xué)院，長沙410082)
摘 要: 采用基于密度泛函理論的第一性原理方法，計算Fe8Al8及(Fe7X)Al8 (X=Pb，Sn，Ti，Cu，Mn，Si，Zn)超胞模型的彈性模量與電子結(jié)構(gòu)，在分析合金化元素改善FeAl金屬間化合物力學(xué)性質(zhì)的基礎(chǔ)上，選取降低脆性效果較好的Cu和最好的Pb，對1.2 mm厚DC56D+ZF鍍鋅鋼和1.15 mm厚6016鋁合金平板試件進行加入中間夾層Cu和Pb的激光搭接焊試驗。結(jié)果表明：FeAl金屬間化合物為脆性相，其電子結(jié)構(gòu)根源在于Fe的sd態(tài)與Al的sp態(tài)存在電子軌道雜化，為明顯的共價鍵特征；FeAl合金化后，脆性降低，相應(yīng)脆性由低到高的順序為(Fe7Pb)Al8、(Fe7Sn)Al8、(Fe7Ti)Al8、(Fe7Cu)Al8、(Fe7Mn)Al8、(Fe7Si)Al8、(Fe7Zn)Al8、Fe8Al8，Pb合金化降低脆性效果最好，激光搭接焊加入中間夾層Pb，鋼側(cè)母材與焊縫界面區(qū)由母材側(cè)較大晶粒和焊縫的細小晶粒交錯形 成，熔池金屬與母材鋁之間沒有明顯的分界線，焊接接頭界面熔合良好；與未加夾層相比，加入中間夾層Cu和Pb后，焊接接頭力學(xué)性能提高，其中Pb的作用優(yōu)于Cu的，試樣斷口均具有韌性斷裂特征。
關(guān)鍵字: 鍍鋅鋼；鋁合金；第一性原理計算；激光搭接焊；FeAl脆性金屬間化合物；力學(xué)性質(zhì)
computation of zinc-coated steel and 6016 aluminum alloy
（1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University,
Changsha 410082, China;
2. School of Materials Science and Engineering, Hunan University, Changsha 410082, China）
Abstract:The elastic moduli and electronic structure were calculated by the first-principle method based on the density functional theory for Fe8Al8 and (Fe7X)Al8 (X=Pb, Sn, Ti, Cu, Mn, Si, Zn) supercell model. Analysis on improving the mechanical properties of FeAl intermetallic compounds was done, Cu and Pb were considered as better elements to reduce the brittleness of FeAl intermetallic compound. The laser lap welding experiments with the Cu or Pb metal sandwich addition were carried out with the DC56D+ZF galvanized steel of 1.2 mm-thick and the 6016 aluminum alloy of 1.15 mm-thick. The results show that the FeAl compound is the brittle phase which attributes to the electron orbit hybridization between the states of Fe-sd and Al-sp with obvious covalent bond characteristics. The brittleness of FeAl compound is reduced with the addition of alloying elements, and the brittleness order from low to high is as follows: (Fe7Pb)Al8, (Fe7Sn)Al8, (Fe7Ti)Al8, (Fe7Cu)Al8, (Fe7Mn)Al8, (Fe7Si)Al8, (Fe7Zn)Al8 and Fe8Al8. The laser lap welding experiment with the Pb metal sandwich addition shows the weld joint contact surface with better fusion based on the fact that the metal of steel side and welded joint frontal zone is made of big crystal grain of metal and tiny crystal grain of welded joint, and the boundary between the pool and metal of aluminum is not obvious. The mechanical properties of the welded joints are improved with the Cu or Pb metal sandwich addition, and the specimen fracture characteristic is ductile.
Key words: zinc-coated steel; aluminium alloy; first-principle computation; laser lap welding; FeAl brittle intermetallic compound; mechanical properties
