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 Fe.sub.44-xCo.sub.6Cr.sub.15Mo.sub.14C.sub.15B.sub.6Tm.sub.x, wherein x represents the atomic percent of corresponding alloy elements and 0x6; 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.

Claims

1. A centimeter-level high-strength Fe-based bulk amorphous alloy, the molecular formula thereof is Fe.sub.44-xCo.sub.6Cr.sub.15Mo.sub.14C.sub.15B.sub.6Tm.sub.x, wherein 0x6, 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 T(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 f 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.sub.3C, FeC, C, B and Tm with a purity of not less than 99 wt. %, respectively; (2) mixing weighted Fe, Co, Cr, Mo.sub.3C, FeC, C, B and Tm, putting them in induction melting quartz tube and closing chamber, when the vacuum degree is below 510.sup.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 510.sup.3 Pa, filing inert gas therein and melting at pressure of 3-7 x10.sup.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 510.sup.3 Pa, filing inert gas therein to 3-710.sup.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.

Description

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

[0019] FIG. 1 is an XRD pattern of a critical size Fe-based bulk amorphous alloy prepared in in embodiment 1;

[0020] FIG. 2 an XRD pattern of Fe-based bulk amorphous alloy bar in 10 mm containing rare earth element Tm prepared in embodiment 1;

[0021] FIG. 3 is a DSC pattern of Fe-based bulk amorphous alloy prepared in embodiment 1;

[0022] FIG. 4 a stress-strain curve of Fe-based bulk amorphous alloy prepared in embodiment 1;

[0023] FIG. 5 is a DC magnetization curve of Fe-based bulk amorphous alloy prepared in embodiment 1;

[0024] FIG. 6 is an integral curve of FC curve magnetization intensity against temperature of Fe-based bulk amorphous alloy prepared in embodiment 1;

[0025] FIG. 7 is DC magnetization difference curve of Fe-based bulk amorphous alloy prepared in embodiment 1;

[0026] FIG. 8 is an integral curve of DC magnetization difference against temperature of Fe-based bulk amorphous alloy prepared in embodiment 1;

[0027] FIG. 9 is an XRD pattern of Fe-based bulk amorphous alloy prepared in embodiment 2;

[0028] FIG. 10 is a morphological photograph of Fe-based bulk amorphous alloy prepared in embodiment 2.

[0029] FIG. 11 is a schematic structural diagram of Fe-based bulk amorphous alloy copper mold casting equipment of embodiment 3.

SPECIFIC DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] The invention is further described below with reference to accompanying drawings.

Embodiment 1

[0031] In the embodiment, a centimeter-level high-strength Fe-based bulk amorphous alloy, the molecular formula thereof is Fe.sub.44-xCo.sub.6Cr.sub.15Mo.sub.14C.sub.15B.sub.6Tm.sub.x, wherein x=0, 2, 4, 6, the diameter thereof is 2 mm, 10 mm, 10 mm, 2 mm respectively, and the preparation method thereof is as follows:

[0032] (1) according to the atomic percent of the molecular formula Fe.sub.44Co.sub.6Cr.sub.15Mo.sub.14C.sub.15B.sub.6, Fe.sub.42Co.sub.6Cr.sub.15Mo.sub.14C.sub.15B.sub.6Tm.sub.2, Fe.sub.40Co.sub.6Cr.sub.15Mo.sub.14C.sub.15B.sub.6Tm.sub.4, Fe.sub.38Co.sub.6Cr.sub.15Mo.sub.14C.sub.15B.sub.6Tm.sub.6, weighting Fe, Co, Cr, Mo.sub.3C, FeC, C, B and Tm with a purity of not less than 99 wt. %, respectively;

[0033] (2) mixing weighted Fe, Co, Cr, Mo.sub.3C, FeC, C, B and Tm in step 1, putting them in induction melting quartz tube and closing chamber, when the vacuum degree is below 510.sup.3 Pa, filing inert gas therein to protect and induction melting, heat-keeping for 10 minutes after melting raw materials, thereafter cutting off the current, and taking out preliminary fused master alloy ingot after preliminary cooling;

[0034] (3) putting the preliminary fused master alloy ingot obtained in step 2 and rare earth element Tm into arc-melting furnace and closing chamber, when the vacuum degree is below 510-3 Pa, filing inert gas therein and melting at pressure of 3-710.sup.4 Pa, after the raw materials are melted, continuously melting for 5 minutes, and then stopping heating, cooling the alloy to solidified with the cooling of the crucible and turning over, repeating the melting for 5 times, an alloy ingot with uniform composition is obtained;

[0035] (4) after removing the surface impurities of the alloy ingot obtained in step 3 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 510.sup.3 Pa, filing inert gas therein to 3-710.sup.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;

[0036] (5) under the protection of inert gas, turning on the power supply arc striking and gradually increasing the current intensity until the alloy pieces are melted, and sucking the molten alloy liquid into the copper mold in corresponding diameter by using pressure difference, a Fe-base bulk amorphous alloy with high amorphous forming ability is obtained.

[0037] As shown in FIG. 1, The XRD patterns, testing by D8 Advance polycrystalline X-ray diffractometer, of Fe-based bulk amorphous alloy prepared in step 5 with high amorphous forming ability, are all diffuse scattering peaks, indicating that the bulk alloy bar is all the same amorphous structure when the diameter thereof is 2 mm, 10 mm, 10 mm, 2 mm, respectively. As shown in FIG. 2, XRD analysis was performed on 10 mm bars of three alloys containing rare earth element Tm, it can be seen that when the rare earth element Tm increases from 4 atomic percent to 6 atomic percent, the alloy easily precipitates various crystal phases including (FeCo) C, -Fe, BC and CrMo.

[0038] The DSC curve (FIG. 3) of Fe-based bulk amorphous alloy prepared in step 5 is measured by using an NETZSCH DSC 404 F3 differential scanning calorimeter, the temperature rise rate is 40 Kelvin/minute, and according to DSC curve, it is obtained that when x=0/2/4/6, the glass transition temperatures Tg of the amorphous alloy are respectively 834K, 850K, 872K and 903K, the initial crystallization temperatures Tx are respectively 895K, 939K, 942K and 959K, and the supercooled liquid region widths T are respectively 61K, 71K, 70K, 56K, as shown in Table 1.

TABLE-US-00001 TABLE 1 Properties of prepared amorphous alloys Thermodynamic Magnetic Mechanical Critical Parameter Property Property Serial Number Alloy Composition Diameter (mm) T.sub.g/K T /K T/K T /K T /K f/Mpa Hv Embodiment 1-1 Fe.sub.44Co Cr.sub.15Mo.sub.14C.sub.15B.sub.6 2 834 895 61 <2 27.7 3013 1170 Embodiment 1-2 Fe Co C Mo C.sub.15B.sub.6Tm.sub.2 10 850 939 71 8.0 23.0 4295 1220 Embodiment 1-3 Fe Co Cr Mo C B Tm.sub.4 10 872 942 70 10.0 22.3 3048 1193 Embodiment 1-4 Fe Co Cr Mo C.sub.15B.sub.6Tm 2 903 959 56 12.0 21.5 2434 1150 indicates data missing or illegible when filed

[0039] The hardness and strength of the alloy are respectively tested by FM-700 microhardness tester and CMT5105 electronic universal testing machine. As shown in Table 1, when x=0/2/4/6, the Vickers hardness of the alloy is respectively 1170, 1220, 1193, 1150, and according to the compressive stress-strain curve shown in FIG. 4, the breaking strength thereof is respectively 3013 Mpa, 4295 Mpa, 3048 Mpa, 2434 Mpa, higher hardness indicates good wear-resisting property, and the breaking strength is much higher than that of super-strength steel, indicating that the bulk amorphous alloy system has good mechanical property.

[0040] The SQUID-VSM type magnetic property measurement system (MPMS) is used to measure the DC magnetization curve of the alloy, and the applied measurement magnetic field is 200Oe. As shown in FIG. 5, with the decrease of the temperature, the magnetization intensity gradually increases from around zero, indicating that the magnetic state of these alloy samples changes from paramagnetic to ferromagnetic at high temperatures. When the temperature of the alloy system continues to decrease, the magnetization intensity appears a peak at about 10-15K, and then gradually decreases, the magnetization curve with field cooling (FC) and the magnetization curve with zero-field cooling (ZFC) are bifurcated at about 3-10K from the state where they basically coincided before, which can be concluded that the Fe-based bulk amorphous system has spinning glass behavior at low temperature. When the temperature continues to decrease, the ZFC curve starts to decrease rapidly with the temperature drop, simultaneously, the FC curve only decreases slowly, because the ZFC curve can show the magnetic moment change of irregularly frozen magnetic ions, and in the process of the temperature decrease, the magnetic moment in the sample is frozen in an irregularly oriented state, thereby the macroscopic magnetization intensity is almost zero; The FC curve mainly shows the magnetic moment of orientedly inducted magnetic ions in an applied field, thereby the magnetic moment arrangement show a certain regularity, and macroscopic magnetization intensity displayed outside is not zero. FIG. 6 is an integral curve of FC curve magnetization intensity against temperature in DC magnetization curve, the temperature corresponding to the point that the absolute maximum value of the minimum value in FIG. 6 against slope of the magnetization curve, is regarded as Curie temperature (Tc). FIG. 7 is a difference curve between the FC curve and the ZFC curve, it can be seen that the spinning glass behavior is most obvious when x=2 in the Fe-based amorphous alloy system, FIG. 8 is an integral curve of DC magnetization difference against temperature, the temperature corresponding to the point that the absolute maximum value of the minimum value in FIG. 8 against slope of the integral curve, is regarded as freezing temperature (Tf). When x=0/2/4/6, freezing temperature (Tf)<2K, 8.0K, 10.0K, 12.0K, the Curie temperature (Tc) is 27.7K, 23.0K, 22.3K, 21.5K, and as shown in Table 1, with the increase of the rare earth element Tm, the freezing temperature of the alloy gradually increases, and the Curie temperature of the alloy gradually decreases.

Embodiment 2

[0041] In the embodiment, a centimeter-level high-strength Fe-based bulk amorphous alloy, the molecular formula thereof is Fe.sub.42Co.sub.6Cr.sub.15Mo.sub.14C.sub.15B.sub.6Tm.sub.x, and the preparation method thereof is as follows:

[0042] (1) according to the atomic percent of the molecular formula Fe.sub.42Co.sub.6Cr.sub.15Mo.sub.14C.sub.15B.sub.6Tm.sub.2, weighting Fe, Co, Cr, Mo.sub.3C, FeC, C, B and Tm with a purity of not less than 99 wt. %, respectively;

[0043] (2) mixing weighted Fe, Co, Cr, Mo.sub.3C, FeC, C, B and Tm in step 1, putting them in induction melting quartz tube and closing chamber, when the vacuum degree is below 510.sup.3 Pa, filing inert gas therein to protect and induction melting, heat-keeping for 10 minutes after melting raw materials, thereafter cutting off the current, and taking out preliminary fused master alloy ingot after preliminary cooling;

[0044] (3) putting the preliminary fused master alloy ingot obtained in step 2 and rare earth element Tm into arc-melting furnace and closing chamber, when the vacuum degree is below 510.sup.3 Pa, filing inert gas therein and melting at pressure of 3-710.sup.4 Pa, after the raw materials are melted, continuously melting for 5 minutes, and then stopping heating, cooling the alloy to solidified with the cooling of the crucible and turning over, repeating the melting for 5 times, an alloy ingot with uniform composition is obtained;

[0045] (4) after removing the surface impurities of the alloy ingot obtained in step 3 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 510.sup.3 Pa, filing inert gas therein to 3-710.sup.4 Pa, melting the alloy pieces by arc-melting, cutting off the current of tungsten electrode, the internal and external air pressure difference of the copper mold suction casting moulding chamber is 0.05 Mpa, the molten alloy is pressed against a copper mold with water cooling under pressure difference to achieve maximum contact, and after cooling, an amorphous alloy ingot is obtained.

[0046] The XRD patterns, testing by D8 Advance polycrystalline X-ray diffractometer, of metallic glass alloy prepared in step 4, are diffuse scattering peaks, as shown in FIG. 9, XRD analysis was performed on 10 mm bars of three alloys containing rare earth element Tm, it can be seen that when the rare earth element Tm increases from 4 atomic percent to 6 atomic percent, the alloy easily precipitates various crystal phases including (FeCo) C, -Fe, BC and CrMo.

Embodiment 3

[0047] The copper mold suction casting equipment used for a novel amorphous alloy copper mold casting method of the invention, as shown in FIG. 11, comprising copper mold suction casting equipment body, wherein the copper mold suction casting equipment body comprises a chamber 2 and a copper mold 4 which are sequentially arranged from top to bottom, at least two copper crucibles 3 are arranged between the copper mold 4 and the chamber 2, an electrode 1 is arranged in the chamber 2 in a penetrating manner, the lower end of the electrode 1 is arranged in the copper crucibles 3, a suction casting mold chamber 7 communicated with the copper crucibles for suction casting is provided in the copper mold 4, the suction casting mold chamber 7 is arranged at the lower ends of the copper crucibles 3, a copper plug 6 is arranged in the suction casting mold chamber 7, water cooling devices 5 are both arranged on the left side and the right side of the suction casting mold chamber 7, and the water cooling devices 5 are arranged in the copper mold 4.

[0048] The chamber 2 is a vacuum electric arc furnace chamber, a plurality of copper crucibles 3 are arranged in the chamber, wherein at least one copper crucible 3 is a copper crucible for suction casting, the other copper crucibles are for melting, the tungsten electrode 1 penetrates through a furnace shell and extends into the copper crucible 3 of the chamber 2, and the copper crucible 3 for suction casting is put into alloy raw materials which are evenly melted according to the required component proportion.

[0049] The novel copper mold casting method uses copper plug 6 in the suction casting chamber mold chamber 7 for traditional cooper suction casting to prevent molten metal from flowing into the chamber 2 under negative pressure.

[0050] The above embodiments are merely preferred embodiments of the invention, and should not limit the invention, and the protect scope of the invention should be defined by the claims, and equivalents of technical features described in the claims are intended to be included in the scope of the invention, that is, equivalent modifications within the scope of the invention are also within the protect scope of the invention.