Synthesis And Properties Of Fe-Cr-based Bulk Metallic Glasses

Fe-based bulk metallic glasses（BMGs）are preeminent in the BMG families from the standpoint of engineering application owing to their high strength,good wear and corrosion resistance,excellent soft magnetic properties,and low material cost.Although the soft magnetic Fe-based metallic glasses have been applied in industrialized production,the developed Fe-based metallic glasses usually have a poor glass-forming ability（GFA）and limited plasticity at room temperature,which hinder their practical use as structure materials.In recent years,spraying the metallic glass powders on the material surface as protective coating has been recognized as an attractive way not only to take advantages of its superior properties but also to extend the applications.The metallic glass powder suitable for thermal spraying technology should exhibit GFA,excellent corrosion resistance and good mechanical properties.A large supercooled liquid region（ΔTx,the interval between the glass transition temperature（Tg）and onset temperature of crystallization）and low Tg are beneficial for thermal spraying as well.The previous developed Fe-Ni-Cr-Mo-P-C-B metallic glasses with low Cr content（≤ 7 at.%）possess good GFA,thermal stability and mechanical properties,but their corrosion resistance still has some space for improvement.In this paper,we investigated the effects of high contents of Cr and Mo additions on the thermal properties,GFA and corrosion resistance of the Fe-Ni-Cr-Mo-P-C-B metallic glasses.And,further improved the corrosion resistance as well as kept the good properties of low Tg、large ΔTx、good GFA and mechanical properties by adjusting the contents of Cr and Mo.The main results of this paper are as follows:1.For the Fe_55-xCr_xNi₂₀Mo₅P₁₂C₄B₄（x = 15–35）metallic glasses,with the increase of Cr content,the thermal stability of supercooled liquid first increased,then decreased,and the GFA decreased gradually.When the content of Cr is 25 at.%,the alloy possess the largest ΔTx of 66 K and the critical diameter for glass-formation is 1.5 mm.2.The Fe_40-yMo_yCr₂₀Ni₂₀P₁₂C₄B₄（y = 5–15）metallic glasses exhibit high thermal stability of supercooled liquid and the ΔTx is about 61–63 K.With the increase of Mo content,the GFA of the alloy decreased gradually.When the content of Mo is 5–10 at.%,the critical diameter for glass-formation is 1–2 mm.3.When the Cr content is 15–30 at.% and the Mo content is 5–10 at.%,the corrosion resistance improved gradually with the increase of Cr and Mo content in H2SO4 and NaCl solutions which is superior to that of SUS316 L stainless steel.However the excessive Mo reduced the corrosion resistance of the alloy.4.（Fe,Cr,Mo）₆₀Ni₂₀P₁₂C₄B₄ bulk metallic glasses show good mechanical properties.i.e.,high fracture strength and Vicker’s hardness of 3191–3477 MPa and 960–1107,respectively.