Al,Ti和Nb对Fe-Ni-Cr-Co-Nb—Ti-Al合金铸态组织的影响

EFFECT OF Al, Ti AND Nb ON CASTING STRUCTURE OF Fe-Ni-Cr-Co-Nb-Ti-Al ALLOYS

对低Al，高Ti,Nb（合金A）和高AI、低Ti，Nb（合金B）两种成分特征的Fe－Ni－Cr－Co－Nb－Ti－Al合金宏观和微观铸态组织的观察分析表明，合金A凝固速度较快，柱状晶区较大：两青枝晶间及铸态晶界上都分布着较多块（厚片）状富含Nb和Ti的MC和Laves相多晶体；合金B柱状晶区晶界Laves相较多；合金A晶界MC和Laves相附近析出魏氏体状γ’和η相及胞状η相；合金B中γ′的尺寸仅约为合金A的1／10研究了凝固过程中，两者晶界MC和Laves相的形成机制和差异，以及两者等轴晶区和往状晶区晶界附近魏氏体状。

Macroscopic and microscopic casting structures of Fe-Ni-Cr-Co-Nb-Ti-Al alloys, inboth low-Al and high-Ti and Nb (alloy A) state and high-Al and low-Ti and Nb (a1loy B) state, werestudied. The results showed that the solidincation rficati0n rate is fasthe area of columnar crystal was largerfor alloy A; a large number of bloky (thick lamellar) MC and Laves polycrystals, which are rich in Nb andTi, distribute between the dendrites and at grain boundaries in both cast alloys; the amount of Laves islarger at grain boundaries in area of columnar crystal in alloy B; the Widmanstatten structure of ry' andp, and the ceIlular structure of n are precipitated nearby MC and Laves phases at grain boundaries inalloy A, the size of 7' in alloy A is ten times as large as that in alloy B. In the areas of equiaxial crystaland columnar crystal during solidification in both alloys, the formati0n mechanism of grain boundary MCand Laves and their difference as well as the difference of Widmanstatten structure, cellular structureand ry' quasi-spheres with larger size nearby the grain boundaries have been studied. The mechanismsforming Widmanstatten structure and cellular structure, and the mechanism transferring 7' to n by meansof stacking fault were discussed.