Trace The Formation Of The Ability To Influence And Mechanical Properties Of Rare Earth On Fecrmocb Department Of Bulk Amorphous Alloys

A series of FeCrMoCB-based non-ferromagnetic bulk metallic glassy(BMG) alloys, i.e. amorphous steels, were prepared by means of copper-mold vacuum suction casting. The glassy structure, thermal stability, glass-forming ability (GFA) and mechanical properties of these alloys with nominal composition of Fe₄₈Cr₁₅Mo₁₄C₁₅B₆M₂(M=Y,Pr,Gd,Tb). and Fe_50-xCr₁₅Mo₁₄C₁₅B₆Gd_x (x= 1,2,4,6) were investigated by differential scanning calorimeter(DSC), X-ray diffraction(XRD), scanning electron microscope (SEM), Vicker's hardness , compression tests and nanoindentation tests. The results are summarized as follows:1) A series of FeCrMoCB-based amorphous steels were prepared by using rare-earth elements Y, Pr, Gd and Tb to substitute 2at.% Fe in Fe₅₀Cr₁₅Mo₁₄C₁₅B₆ system. The maximum BMG dimension of Fe₄₈Cr₁₅Mo₁₄C₁₅B₆M₂(M=Y,Pr,Gd,Tb) is 8mm, 3mm, 12mm, 12mm, respectively. The glass-forming ability (GFA) of FeCrMoCB-based amorphous steels increases first with increasing Gd content, when the Gd content is 2at.%, the GFA reaches to the maximum then the GFA decreases later when Gd content beyond 2at.%. And it is difficult to prepare full BMG alloys with a diameter of 5mm by increasing alloying elements to 6 at %.2) The effects of the alloying non-rare-earth elements, such as, Hf, P, Si and Co, on the GFA of FeCrMoCB-based BMG alloys were studied. Hf element cannot markedly improve the GFA, P addition even will reduce the GFA, but Si, Co addition maybe have a positive effect on the GFA.3) All the Fe₄₈Cr₁₅Mo₁₄C₁₅B₆M₂(M=Y,Pr,Gd,Tb) BMG alloys exhibit multi-stage crystallization, of which glass transition temperature (T_g) is about 550℃, and the onset temperature of crystallization (T_x) is above 600℃, the supercooled liquid region ( T_x) is in between 49.8℃ and 75.9℃. Fe₄₈Cr₁₅Mo₁₄C₁₅B₆M₂ (M=Y,Gd,Tb) BMG exhibits a good GFA and thermal stability. In the Fe_50-xCr₁₅Mo₁₄C₁₅B₆Gd_x(x=2,4) BMG, when Gd increases from 2at.% to 4at.%, the glass transition temperature (T_g) decreases to 543.3℃, the onset temperature of crystallization(Tx) increases and the supercooled liquid region( T_x) increases from 59.2 ℃ to 73.0℃.4)In the Fe₄₈Cr₁₅Mo₁₄C₁₅B₆M₂(M=Y,Gd,Tb) BMG alloys, when the sample dimension is in between 5mm and 10mm, their Vicker's hardness is about 1348.3, 1170.6, 1233.3Hv,respectively and almost keeps constant. The Vicker's hardness of Fe4gCri5Moi4Ci5B6Gd2 and Fe48Cri5Moi4Ci5B6Tb2 decreases approximately from 1400Hv to HOOHv as the sample dimension increases from 3mm to 12mm. The Hv of Feso.xCri5Moi4Ci5B6Gdx(x=l,2,4,6) increases first and decreases later with increasing Gd content. There is likely a good correlation between the Vicker's hardness of and the dimension in Fe48Cri5Moi4Ci5B6M2(M= Y,Pr,Gd,Tb) BMG alloys.5) The fracture strength (ocf.) for Fe48Cri5Moi4Ci5B6M2(M=Gd,Tb) BMG alloy is in the range of 650 to 900MPa and elongation(Ef) is in between 0.40% and 1.78 %. The compressive fracture angles are about 0°. The elongation (ef) for Fe48Cri5Moi4C|5B6M2(M=Gd,Tb) with 5mm is slightly higher and some plastic deformation occurs.6) The nanoindentation of BMG rods with 5mm diameter has been carried. The Young' moduli, HV and nanoindentation hardness are as follows:AlloysYoung's modulus(GPa)HvNanoindentation hardness (GPa)FftwCruMoMCuBsGdj236.61231.713.30234.51178.912.73rCdACri