中文摘要：

配制和电弧熔炼了MoSi2、（Mo,2at%Nb）Si2、（Mo,6at%Nb）Si2、Mo（Si,2at%Al）2、Mo（Si,4at%Al）2和（Mo,2at%Cr）Si2六种合金,用XRD、SEM-EDS、EPMA、维氏硬度计及压痕法研究了Nb、Al、Cr合金化对MoSi2组织结构、室温硬度及断裂韧性的影响。结果表明,2at%Al、4at%Al和2at%Cr三种合金均得到了单一四方C11b相;6at%Nb合金因Nb含量高,导致部分四方C11b相转变为六方C40相,合金出现灰色C11b基体相与亮白色层片状C40第二相双相组织,部分C40相中存在几乎平行排列的宽度贯穿裂纹。Nb、Al、Cr合金化都降低了MoSi2的维氏硬度,提高断裂韧性,其中2at%Nb、4at%Al合金的断裂韧性最高,达到了5.90MPa.m1/2,提高了69%。

英文摘要：

Six kinds of MoSi2, （ Mo,2at% Nb） Sis, （ Mo,6at% Nb） Si2, Mo（ Si,2at% Al）2, Mo（ Si ,4at% Al）2 and （ Mo, 2at% Cr） Si2 alloys were are-melted. The effects of Nb, Al and Cr alloying on mierostrueture, hardness and fracture toughness of MoSi2 at ambient temperature were investigated by means of XRD, SEM-EDS, EPMA, Viekers and indentation toughness method. The results show that all of the three alloys with 2at% Al,4at% Al and 2at% Cr have only obtained tetragonal C11b phase; while in the alloy with 6at% Nb, the addition of excessive Nb leads tetragonal C11b phase to transform partly into hexagonal C40 phase, thus the dual-phase mierostrueture with grey C11 b matrix and whiter lamellar CAO phase was observed in this alloy. Also, there are some cracks crossing lamella in the width and almost arranging parallelly in some C40 phase. Nb, Al and Cr alloying are found to decrease hardness and improve fraeture toughness of monolithic MoSi2. The alloys with 2at% Nb and 4at% Alhave highest fracture toughness ,reaching 5.90 MPa.m^1/2 ,69% higher than that of monolithic MoSi2.