Centimeter-level High-strength Iron-based Bulk Amorphous Alloy and Novel Copper Mold Casting Method Thereof

Abstract

The invention discloses a centimeter-level high-strength iron-based bulk amorphous alloy and novel copper mold casting method thereof; the molecular formula thereof is Fe44-xCo6Cr15Mo14C15B6Tmx, wherein x represents the atomic percent of corresponding alloy elements and 0≤x≤6; the novel copper mold casting method comprising: directly cooling a copper mold with cooling water under negative pressure through electric arc melting to obtain an amorphous alloy ingot; the alloy has the remarkable characteristics of high amorphous forming ability, high strength and high hardness, by the conventional casting, the maximum critical diameter can be 10 mm, the highest strength can be 4295 Mpa, and the highest Vickers hardness can be 1220 Hv; meanwhile, the alloy has obvious spinning glass behavior at low temperature; the preparation method has low cooling rate, is free from the limitation of mold diameter, and can directly obtain the amorphous alloy ingot, the cost is reduced, and the maximum diameter of the amorphous alloy ingot is 16.52 mm; and by the preparation method, the amorphous forming ability of the bulk amorphous alloy can be determined more accurately.

1 . A centimeter-level high-strength Fe-based bulk amorphous alloy, the molecular formula thereof is Fe 44-x Co 6 Cr 15 Mo 14 C 15 B 6 Tm x , wherein 0≤x≤6, and x represents the atomic percent of rare earth element Tm. 
     
     
         2 . The centimeter-level high-strength Fe-based bulk amorphous alloy of  claim 1 , wherein the structure of the Fe-based bulk amorphous alloy is fully amorphous structure, and critical diameter thereof is 2-10 mm. 
     
     
         3 . The centimeter-level high-strength Fe-based bulk amorphous alloy of  claim 1 , wherein the glass-transition temperature Tg thereof is 834-903K, the crystallization temperature Tx thereof is 895-959K, the supercooled liquid region ΔT(Tx-Tg) is 56-71K. 
     
     
         4 . The centimeter-level high-strength Fe-based bulk amorphous alloy of  claim 1 , wherein Vickers hardness Hv thereof is 1150-1220, the breaking strength σf thereof is 2434-4295 Mpa. 
     
     
         5 . The centimeter-level high-strength Fe-based bulk amorphous alloy of  claim 1 , wherein the Fe-based bulk amorphous alloy has obvious spinning glass behavior at low temperature, there is obvious bifurcation between the zero field-cooling curve and field-cooling curve in the DC magnetization curve, the freezing temperature Tf<2-12K and the Curie temperature TC is 21.5-27.7K. 
     
     
         6 . A copper mold casting method for the centimeter-level high-strength Fe-based bulk amorphous alloy according to  claims 1 - 5 , comprising following steps:
 (1) according to the atomic percent of the molecular formula, weighting Fe, Co, Cr, Mo 3 C, FeC, C, B and Tm with a purity of not less than 99 wt. %, respectively;   (2) mixing weighted Fe, Co, Cr, Mo 3 C, FeC, C, B and Tm, putting them in induction melting quartz tube and closing chamber, when the vacuum degree is below 5×10 −3  Pa, filing inert gas therein and induction melting, heat-keeping for 10 minutes after melting raw materials, thereafter cutting off the current, and after preliminary cooling, taking out preliminary fused master alloy ingot;   (3) putting the preliminary fused master alloy ingot and rare earth element Tm into arc-melting furnace and closing chamber, when the vacuum degree is below 5×10 −3  Pa, filing inert gas therein and melting at pressure of 3-7 x10 4  Pa, after the raw materials are melted, continuously melting for 3-10 minutes, and then stopping heating, cooling the alloy to solidified and turning over, repeating the melting for 3-6 times, an alloy ingot with uniform composition is obtained;   after removing the surface impurities of the alloy ingot and cleaning it, breaking the alloy ingot into small pieces, taking small pieces of alloy ingot and putting into copper crucible of the copper mold suction casting equipment, when the vacuum degree is below 5×10 −3  Pa, filing inert gas therein to 3-7×10 4  Pa, melting the alloy pieces by arc-melting, the internal and external air pressure Difference of the copper mold suction casting moulding chamber is 0.05 Mpa, and sucking the molten alloy liquid into the copper mold, a Fe-base bulk amorphous alloy with high amorphous forming ability is obtained.