CN100393912C

CN100393912C - Magnesium-zirconium alloying

Info

Publication number: CN100393912C
Application number: CNB038047934A
Authority: CN
Inventors: 马前; 戴维·圣约翰; 马尔科姆·T·弗罗斯特
Original assignee: Cast Centre Pty Ltd
Current assignee: Cast Centre Pty Ltd
Priority date: 2002-01-18
Filing date: 2003-01-20
Publication date: 2008-06-11
Anticipated expiration: 2023-01-20
Also published as: TW200302285A; EP1466038A1; AU2003201396B2; DE60330309D1; EP1466038B9; US20050161121A1; CN1639389A; EP1466038A4; EP1466038B1; ATE450634T1; WO2003062492A1

Abstract

Zirconium sponge can be chemically depassivated by treatment with hydrofluoric acid to improve the ability of molten magnesium/magnesium alloy to dissolve zirconium from the treated zirconium sponge and to form a melt containing substantially evenly distributed particles of zirconium.

Description

Magnesium-zirconium alloying

Invention field

The present invention relates in pure magnesium or magnesium alloy, add zirconium, and relate to the preparation of magnesium-zirconium (Mg-Zr) alloy that comprises the Mg-Zr mother alloy.

Background of invention

For contain negligible quantity, can with zirconium form stable compound, such as the magnesium alloy of the element of Ai, Si, Fe, Ni, Co, Sn and Sb, zirconium is a kind of effective grain-refining agent.The zirconium that adds about 1 weight % in this magnesium alloy can easily cause under common rate of cooling, and particle diameter reduces 80% or more.This special grain refining capability makes zirconium become a kind of important alloying element that is not melt into the magnesium alloy of alloy with Al and Si.For example, provide the particular combinations of a kind of high temperature and room-temperature property such as the zirconic Mg-RE-Zn alloy of EZ33 (Mg-3.3RE-2.7Zn-0.6Zr) and ZE41 (Mg-1.2RE-4.2Zn-0.7Zr), and this is unreachable to the Mg-Al-Zn alloy.

The solubleness of zirconium in the pure magnesium of fused is about 0.6%, and it increases slightly along with the increase of melt temperature.Existing report: the microstructural notable attribute that contains greater than the magnesium alloy of the soluble zirconium of tens percentage ratios is to have rich zirconic core in most of magnesium granules.The zirconic core of this richness is considered to peritectoid solidified product.In order to obtain excellent grain refining in scale operation, all zirconium content of dissolving in the melt of magnesium (that is: about 0.6%) meets the requirements.

In decades, worked out zirconium be incorporated into various means in the molten magnesium, having comprised:

(a) the zirconium metal with various forms is melt into alloy;

(b) be melt into alloy with zirconium sponge;

(c) be melt into alloy with the Zn-Zr mother alloy;

(d) and ZrO ₂Be melt into alloy;

(e) with the halogenide or the complexing halogenide of various zirconiums or have various such as NaCl, KCl, BaCl ₂, NaF, KF etc. the halogenide and/or the halid mixture of complexing of salt be melt into alloy together; With

(f) be melt into alloy with the Mg-Zr mother alloy.

Saunders and Strieter (W.P.Saunders and F.P.Strieter, " in magnesium, fuse zirconium ", U.S. foundry work association proceedings, 1952,60 volumes, the 581-594 page or leaf) and Emley (E.F.Emley, " magnesium industry principle ", pergamon press, Oxford University, 1966,127-155 page or leaf) discussed each merits and demerits in these means in detail.Since about nineteen sixty,, only there has been the Mg-Zr mother alloy to obtain the wide industrial application as being melt into the zirconium source of alloy with magnesium.The Mg-Zr mother alloy of this rich Zr is by the chemical reduction with magnesium makes based on the salt mixture of Zirconium tetrafluoride or zirconium chloride.These two kinds of mother alloys are substantially the same and contain the zirconium of 1/3rd weight of having an appointment.A kind of in the two, by MagnesiumElektron limited liability company (MEL) about 1945 by obtaining with molten magnesium chemical reduction complexing Zirconium tetrafluoride, be called as Zirmax (trade mark) for a long time.In the U.S.,, developed a kind of kind of similar Mg-Zr mother alloy according to the reduction process of chlorate.

The mother alloy of Zirmax type is kept for the industrial basic Zirconium alloy material of zirconic magnesium alloy.Zirmax contains have an appointment 33% zirconium and 67% magnesium, and most of zirconium is that zirconium particle form (mainly in submicron in 10 mu m ranges) with all size is present in the magnesium matrix.

Zirmax type mother alloy become be used to contain the standard zirconium source of zirconium magnesium alloy before, study being melt into alloy with various forms of zirconium metals.

Sauerwald in nineteen forty-seven publish about the zirconium metal-powder being fused to the work (V.F.Sauerwald that goes in the magnesium, " Dus Zustandsdiagram Magnesium-Zirkonnium ", zeitschrift furanorganische Chemie., 1947,255 volumes, the 212-220 page or leaf).Under all temps between 680 and 1100 ℃, in the argon atmospher, 5 weight % zirconium metal-powders are joined in the magnesium.At the soluble zirconium content (sample digestion in HCl acid) that has all obtained to surpass 0.5 weight % under all probe temperatures.In the same year, Ball has reported work (C.J.P.Ball, " Metallurgia ", 1947,35 volumes, 125-129; 211 pages), its statement: under 900-1100 ℃, in the argon atmospher, metal zirconium is dissolved in the magnesium, but this is a kind of difficulty and expensive method.Because the evaporation of magnesium, operating in the scale operation under this temperature is infeasible.Emley has reported (E.F.Emley, " faraday learns to discuss ", 1948-49 in 1948,47 volumes, No.4,219 pages): because the zirconium metal-powder is expensive and be highly combustible, so consider the possibility that is melt into alloy by reducible zirconium compounds naturally.

In nineteen fifty-two, Saunders and Strieter have reported their research, wherein studied under 760 ℃ (1400F), added material as the zirconium alloy that is used for magnesium with the metal zirconium (that is: the ductility zirconium and the zirconium powder of zirconium sponge, fusion zirconium, iodide decomposition) of various forms.This frit zirconium joins in the little ladle with the bulk of 6.35mm (1/4 inch), and stirs in this ladle with steel bar.Stir after 30 minutes, apparent solution do not occur.The analysis of this melt has shown the add-on for 1% zirconium, and the result of 0.03% soluble zirconium content is arranged.Be rolled onto 127-254 μ m (0.005-0.010 inch) and be cut into the square iodide process zirconium sheet of 6.35mm (1/4 inch), use the mode of frit zirconium to add to be similar to.It stirs several minutes in ladle.Find: keeping temperature after 65 minutes, for the add-on of 1% zirconium, the soluble zirconium content of generation only reaches 0.1%.By adding the application of estimating zirconium powder by different way,, and have to use some protection powder with not oxidated method because zirconium powder is spontaneous combustion.Zirconium powder and various tackiness agent are made the ball shape, zirconium powder is sealing in the magnesium capsule of sealing, with zirconium powder and magnesium powder pressed compact, and with sintering zirconium powder pressed compact form use zirconium powder.Usually, for the add-on that joins 3% zirconium in the Mg-5Zn melt, the zirconium content of report resultant changes between 0.7 and 0.85%.The solubleness of zirconium in magnesium is subjected to the influence of the existence of element.According to reports: under the existence for 3.4% the Zn of having an appointment, the solubleness of Zr in magnesium can be increased to slightly greater than 0.7% from 0.6%, and 5% zinc makes the solubleness of Zr in magnesium be increased to about 0.8%.

Said according to Saunders and Strieter, the zirconium test according to various metal forms is melt into alloy with zirconium sponge and has illustrated most promising result.Used zirconium sponge makes by Kroll (Kroll) reduction method:

((a) uses chlorine and carbon at Zirconium oxide, for example zircon (ZrSiO ₄) baddeleyite (ZrO ₂) go up reaction and make zirconium tetrachloride

ZrO ₂+ 2Cl ₂+ 2C (900 ℃) → ZrCl ₄+ 2CO, or

ZrSiO ₄+4Cl ₂+4C(900℃)→ZrCl ₄+SiCl ₄+4CO；

(b) the resultant zirconium tetrachloride is separated from iron trichloride (from iron contamination) and silicon tetrachloride (if existence) by fractionation; With

(c) zirconium tetrachloride of this purifying makes " zirconium sponge "---ZrCl by reacting to reduce with molten magnesium in argon gas ₄+ 2Mg (1100 ℃) → Zr+2MgCl ₂).

In their experiment, this sponge is ground to mean particle size basically and is reduced to about 12.7 μ m or 0.0005 inch.The result shows: for the add-on of 3% zirconium, after stirring in 3-4 minute, zirconium sponge has produced the soluble zirconium content of about 0.62-0.66% in the Mg-5Zn alloy.For the add-on of 1% zirconium sponge, obtained the soluble zirconium content in 0.32 to 0.52% scope.In addition, the author finds: because when particle becomes thinner powder, this material below it can be immersed in melt before burning totally, therefore when the size minimizing of this sponge fragment, be melt into the efficient reduction of alloy.Therefore, have to use some protection powder in case the method for oxidation.

Although illustrated excellent alloying result in the work of Saunders and Strieter, zirconium sponge be melt into alloy in magnesium, be limited in laboratory scale usually about the zirconium sponge of kroll reduction process.Realize and point out as Saunders and Strieter: " the industrial application zirconium sponge significant drawback is in the magnesium alloy field: this material is melt into alloy needs suitable painstaking efforts ".This painstaking efforts obviously are at grinding technics, because applied fusion method, i.e. 3-4 minute stirring is obviously simple.In addition, the inevitable pollution problem that occurs in grinding technics is another significant drawback in the industrial application zirconium sponge.

In " magnesium technology principle ", Emley has carried out similar commentary in the magnesium to the zirconium metal being melt into alloy: " the pure zirconium metal that obtains with any approach all is expensive and its powder morphology is highly combustible; owing to these reasons; be easy to combine with it and make it by oxygen, hydrogen and polluted by nitrogen, and is also not obvious best by the approach of zirconium metal ".

Test shows: in the scale operation of magnesium alloy, when advantageously adding on a large scale when being dissolved in the magnesium melt under the speed, can easily observe undissolved zirconium particle to Zirmax in the microstructure of the magnesium alloy that makes.(Ma Qian, L.Zheng, D.Graham, D.H.StJohn and M.T.Frost, " undissolved zirconium particulate precipitation in the pure magnesium melt ", light metal periodical, 2001, volume 1, No.3,157-165 page or leaf; And Y.Tamura, N.Kono, T.Motegi and E.Sato, " the grain refining mechanism and the cast structure of Mg-Zr alloy ", Japanese light metal association periodical, 1998, volume 48, No.4,185-189 page or leaf).A lot of these residual (undissolved) zirconium particles have the mean particle size of about 5 μ m.

The density of zirconium is 6.5gcm ^-3, and the density of molten magnesium is 1.6gcm ^-3Unless therefore violent stirring, the zirconium particle has settled strong tendency in the magnesium melt.Particle is big more, and it is just fast more that it is deposited to the melt bottom.For example, have been found that under 780 ℃ that one 15 microns zirconium particle is with the rate sedimentation of the about 40 mm/min bottom to the magnesium melt, and therefore under this temperature, be difficult to keep this particle suspension in melt.On the contrary, under uniform temp, when this particle diameter during less than 3 microns, it can be easy to be suspended in the magnesium melt.

Chambers science and technology dictionary (1991) definition: " passivity " be " metal or mineral surface lack with that clean, new exposed surface on the response of the chemical erosion that takes place.Because various factors, comprising: by aging, oxygenizement or pollute the insoluble film that produces; The surface energy of discontinuous lattice reduces; Adsorption layer ... ".Run through whole specification sheets, term " depassivation ", " by depassivation ", " at depassivation " are understood that to have the implication that derives from the definition of " passivity " above.

Summary of the invention

First aspect the invention provides a kind of method that is used to handle the zirconium metal, and this method comprises chemical depassivation zirconium metal.This zirconium metal is preferably with the zirconium sponge of the method for zirconium sponge that form to handle.Can be by handling this zirconium sponge of chemical depassivation with fluoride sources.This fluoride sources can be hydrofluoric acid.This fluoride sources can be the mixture of hydrofluoric acid and nitric acid.

This hydrofluoric acid preferably has the concentration between 0.10% and 50.0%, more preferably between 0.50% and 5.0%, most preferably between 1.5% and 2.5%, for this acid concentration, calculates shown in hereinafter as this specification sheets.These acid concentration scopes correspond respectively to the 0.05-50.0 volumetric molar concentration, 0.25-2.63 volumetric molar concentration and 0.76-1.28 volumetric molar concentration, and it can be approximately the 0.05-50.0 volumetric molar concentration, 0.25-3.0 volumetric molar concentration and 0.75-1.5 volumetric molar concentration.

Second aspect the invention provides a kind of method of handling zirconium sponge, and this method comprises with this zirconium sponge of solution-treated that contains fluorion to form the zirconium sponge of handling.

This zirconium sponge is preferably zirconium particulate porous agglomerate.Preferably, this sponge forms by kroll reduction process.

Preferably, this sponge comprises zirconium and unavoidable impurities.Hafnium is a kind of common impurities in the zirconium.On the contrary, Fe, Ni, Al, Si, C, Co, Sn and Sb are as the inhibition of alloying and do not wish to contain, and their total concn is more preferably less than 0.5% preferably less than 1%.

Preferably, the physical form of this zirconium sponge is that small-particle and each particle have vesicular structure.Preferably, these zirconium sponge particles have following performance:

-this particulate mean particle size between 0.1 to 10mm, more preferably 0.5 and 5mm between

-this particulate minimum size is 0.5mm, and more preferably 1mm and overall dimension are 10mm, more preferably 5mm

Density=5.2-6.3g/cm of-sponge ³, more preferably 5.5-5.8g/cm ³

The porosity of-sponge (density of the density of 1-sponge/solid zirconium)=0.08-0.2, more preferably 0.11-0.15.

Hole size on-each zirconium sponge particulate polished cross-sections is usually between 5 and 60 μ m.

The third aspect the invention provides by according to the present invention first or the zirconium sponge of the processing that makes of the method for second aspect.

Compare with undressed (primary sample) zirconium sponge, have been found that: ability and formation that the processing to zirconium sponge according to the present invention has improved molten magnesium dissolving zirconium contain equally distributed basically zirconium particulate melt.

Fourth aspect the invention provides the zirconium sponge that comprises the zirconium particle cluster, and it has to small part and is coated to the top layer that fewer particulate contain fluorochemicals.This fluorochemicals is preferably the fluorochemical of zirconium and can is that chemical formula is Zr _xF _yNH ₂The compound of O.

The 5th aspect the invention provides a kind of method of producing magnesium-zirconium mother alloy, and this method may further comprise the steps:

(a) zirconium sponge of described processing according to a third aspect of the invention we or described according to a forth aspect of the invention zirconium sponge are mixed with molten magnesium with formation contain dissolving zirconium and zirconium particulate magnesium-zirconium melt; With

(b) cast this magnesium-zirconium melt to be cured as magnesium-zirconium mother alloy.

Preferably, this sponge mixes with molten magnesium by stirring.

Aspect the 6th, the invention provides a kind of magnesium that obtains by the method manufacturing of fifth aspect present invention-zirconium mother alloy.Preferably, this mother alloy contains 10%-50% in magnesium/magnesium alloy, more preferably the zirconium of 20%-40%.Preferably, at least 90% zirconium particulate size is more preferably less than 3 μ m less than 5 μ m in this mother alloy.Preferably, mean particle size is less than 5 μ m.

Aspect the 7th, the invention provides a kind of magnesium-zirconium mother alloy, it contains does not have the dissolving of halide impurities zirconium and zirconium particle basically, and wherein 90% zirconium particulate size is less than 5 μ m, preferably less than 3 μ m.

Preferably, this mother alloy of casting is a blank, and this term is interpreted as and comprises briquet, pellet etc.

In eight aspect, the invention provides and a kind ofly add zirconium in the molten magnesium method as alloying element, this method comprises: the zirconium sponge of the zirconium sponge of the processing of a third aspect of the present invention or a fourth aspect of the present invention is mixed with magnesium/magnesium alloy.

Aspect the 9th, the invention provides and a kind ofly add zirconium in the molten magnesium method as alloying element, this method comprises: the described magnesium in the of the present invention the 6th or the 7th aspect-zirconium mother alloy is mixed with molten magnesium.

Preferably, add in the molten magnesium the zirconium amount greater than under the temperature of this melt with the saturated magnesium/magnesium alloy of zirconium needed amount.

Aspect the tenth, the invention provides a kind of zirconic magnesium alloy that makes by the method for the present invention the 8th or the 9th aspect.

The accompanying drawing summary

In order to understand the present invention more fully, existing with reference to the accompanying drawing of mentioning below, by embodiment, preferred embodiment and other main points of the present invention are described.

Fig. 1 (a)-(c) is for illustrating when adding in the pure magnesium Photomicrograph of the grain refining capability of primary and undressed zirconium sponge under 730 ℃.The magnification of these three Photomicrographs is identical.Fig. 1 (a) be pure magnesium, Fig. 1 (b) for after adding the undressed zirconium sponge of 1wt%, stir and Fig. 1 (c) be again succeeded by 30 minutes manual stirring after adding the undressed zirconium sponge of 1wt% in addition succeeded by 30 minutes manual.

Fig. 2 (a)-(c) is for illustrating when adding in the pure magnesium Photomicrograph of the grain refining capability of primary and undressed zirconium sponge under 780 ℃.Identical among the magnification of these three Photomicrographs and Fig. 1 (a)-(c).Fig. 2 (a) be pure magnesium, Fig. 2 (b) for after adding the undressed zirconium sponge of 1wt% succeeded by 2 minutes manual the stirring, kept 30 minutes down and Fig. 2 (c) be 780 ℃ of further maintenances 210 minutes down at 780 ℃ then.

Fig. 3 (a)-(c) is for illustrating when adding in the pure magnesium Photomicrograph of the grain refining capability of the zirconium sponge of processing of the present invention under 680 ℃.The magnification of these three Photomicrographs and above-mentioned accompanying drawing identical.Fig. 3 (a) be pure magnesium, Fig. 3 (b) for after adding the zirconium sponge that 1wt% handled succeeded by 20 minutes manual stir and Fig. 3 (c) for further by hand after the stirring 10 minutes.

Fig. 4 (a)-(c) is for illustrating when adding in the pure magnesium Photomicrograph of the grain refining capability of the zirconium sponge of processing of the present invention under 730 ℃.The magnification of these three Photomicrographs and above-mentioned accompanying drawing identical.Fig. 4 (a) is pure magnesium, Fig. 4 (b) for stirring and Fig. 4 (c) is further stirring 2 minutes by hand again after keeping 30 minutes succeeded by 30 minutes manual after adding the zirconium sponge that 1wt% handled.

Fig. 5 (a)-(c) is for illustrating when adding in the pure magnesium Photomicrograph of the grain refining capability of the zirconium sponge of processing of the present invention under 800 ℃.The magnification of all Photomicrographs and above-mentioned accompanying drawing identical.Fig. 5 (a) is pure magnesium, Fig. 5 (b) for stirring and Fig. 5 (c) is further stirring 2 minutes by hand again after keeping 30 minutes succeeded by 30 minutes manual after adding the zirconium sponge that 1wt% handled.

Fig. 6 is used for the photo of profile of undressed (primary sample) zirconium sponge of one embodiment of the invention for expression.

Fig. 7 is the Photomicrograph of the view of the zirconium sponge particulate typical microstructure after the expression process processing of the present invention shown in Figure 6.

Fig. 8 is the Photomicrograph of another the microstructural view of zirconium sponge particulate after the processing of the present invention of demonstration process shown in Figure 6.

Fig. 9 adds the synoptic diagram of the zirconium sponge the handled method in the molten magnesium for explanation.

The microstructural representative view of the blank of the mother alloy that Figure 10 and 11 expressions make according to the present invention.

The typical diagrammatic sketch of Figure 12 and the commercially available Zirmax mother alloy of 13 expressions.

The microstructural representative view of the blank of the mother alloy that Figure 14 and 15 expressions make according to the present invention.

Figure 16 stays the Photomicrograph of handling the reaction product on the zirconium sponge particle of back through of the present invention for expression.

Embodiment

Simultaneous test

Selecting zirconium sponge particulate physical form diameter is undressed (primary sample) zirconium sponge of 1-10mm.Major impurity in this sponge is a hafnium.Impurity concentration is:

Hf=about 0.8%

Fe+Cr＝0.1％

C＝0.004％

H＝0.001％

N＝0.002％

Without processing of the present invention, under 730 and 780 ℃, sponge is added in the sample of two molten magnesiums respectively.The different time collect conical sample (Φ 30 * Φ 20 * 25mm), and detect shows the evidence (referring to Fig. 1 and Fig. 2) that does not almost demonstrate grain refining, in addition when this melt 780 ℃ of maintenances in the time of 2 to 6 hours down.The wet chemical analysis of the soluble zirconium content in the sample of use 15%HCl acid demonstrates insignificant zirconium content (＜0.05%).

The preparation of the zirconium sponge of handling

At first will impregnated in a kind of acidic solution that makes with following method with employed identical zirconium sponge in the above-mentioned simultaneous test:

The concentrated nitric acid (68.5%-69.5%) of mixing 45ml and the dense hydrofluoric acid (50%) of 45ml also are diluted to 1000ml altogether in water.This provides a kind of about 3%HNO that contains ₃With the acidic solution of 2%HF, it is equivalent to the HF of about 1.1 volumetric molar concentrations and the HNO of 0.5 volumetric molar concentration ₃

This zirconium sponge was placed in this acid solution 5 minutes.Observed bubble, this shows that this acid may remove ZrO at least in part ₂Layer is also dissolving some the zirconium metals below it.After shifting out from this acid solution, in ethanol, clean this zirconium sponge, and under heating lamp about 50 ℃ dry 60 minutes down.The also deemed appropriate clean-out system of water.

Be used for preparing the zirconium sponge of the processing of the alloy that Fig. 3-5 describes, it is same as the HF solution 5 minutes that is used for simultaneous test by zirconium sponge be impregnated in, then cleans and dry making at water.This HF solution is to provide about 2.25%HF by the dilution dense HF of 45ml (50%) in water to 1000ml altogether, and it is equivalent to about 1 volumetric molar concentration HF and makes.

The optional acid solution that can successfully use is 0.07-0.25%HF.This is very rare HF acid solution and operation easily.

The zirconium sponge of handling is be same as the 2%HF solution 4 minutes that is used for simultaneous test by zirconium sponge is immersed, then clean and dry making at water.The reaction product of this processing is tangible as the white on the sponge particle among Figure 16 mutually.

Comprise from Zr surface dissolution or some physical property removing oxide compound that though it is believed that the processing of success we do not wish by any about why the effective theory of this processing fetters.

To the results are shown in the following table 1 that sponge particulate XPS analysis that handled and undressed provides.The particle of handling was dipped in the 0.5%HF solution 4 minutes, and water cleans and is dry.Analyze for each that provides, all the layer collection data of dark 5 nanometers or 10 atoms from the surface of six particles with different sizes.

Table 1 that handled with undressed sponge particulate XPS analysis

According to the energy level that every kind of element is recorded, in three kinds of situations of all researchs, O is with ZrO ₂Form exist, and the F that records in the particle of handling is with such as ZrF ₄Zr _xF _yNH ₂The form of O exists.

In the Total Test that carries out, observe: this sponge particulate weight reduces along with the increase in treatment time in acid solution, runs out of up to all particle disappearance or HF.

Though we are without wishing to be bound to any theory, we think at present: mechanism is that processing causes the oxide film on each sponge particle partially or completely to be removed, and the continuous or discontinuous reaction product layer of formation one deck (may be Zr on this particle _xF _yNH ₂O).Owing on this sponge particle, form Zr _xF _yNH ₂The sticking patch of O or coating are so after processing, can prevent the oxidation of the zirconium under these sticking patch or coating.Think: this sticking patch is dissolved in the molten magnesium subsequently, provides fresh contact site thereby stay the zirconium surface portion that is exposed to this molten magnesium for this molten magnesium.The BSE image discloses: have many small pipelines in each sponge particle, this provides explanation for this sponge particulate decomposes.

The mechanism that proposes above only is provided as the possible explanation of test-results, and may have other mechanism.The present invention can combine with described mechanism, but can not think and be limited by it.

The preparation of magnesium-zirconium alloying

In a small pieces magnesium ingot, process a hole, and as shown in Figure 9, the required fragment of the zirconium sponge of handling is put in this hole.Then this sheet blank promptly is immersed to the magnesium melt surface below.This makes the zirconium sponge of handling be introduced directly in the melt, and does not remain on the lip-deep possibility of this melt.The sponge that this method has been avoided handling is trapped in slag, and has avoided the sponge of handling not wetting by melt.Can this sponge be joined in the melt with various alternate manners, such as by adding a kind of sponge particulate agglomerate, as long as its successfully be introduced into the surface below.

In addition, have been found that: the zirconium sponge particle can directly join in the melt under certain conditions.An example is: if magnesium bath surface quilt is such as 1%SF ₆(surplus: 49.5%CO ₂With 49.5% dry air) blanketing gas protect, and thereby the oxygen concn of the surface of magnesium melt very low, as long as so operation rapidly, this sponge particle can successfully directly add.For example, the zirconium sponge particle can leave the high place adding of bath surface 800mm by the steel funnel, and wherein the bottom of this funnel is placed on this bath surface just.This makes the sponge particle promptly enter into melt and is not oxidized.This be proved to be a kind of make tiny (＜5mm) the zirconium sponge particle adds the mode very easily in the magnesium melt to.

After the speed adding of the zirconium sponge of handling with 1 weight %, this melt keeps several minutes and arrives correct temperature with reheat, stirs then 30 minutes.Three temperature have been used: 680 ℃, 730 ℃ and 800 ℃.After the zirconium sponge of handling adds, collect conical sample in the different time.

Fig. 3-5 has shown the typical diagrammatic sketch of the grain pattern that obtains respectively from these three tests.

The results are summarized in the table 2 of wet chemical analysis wherein listed the wet chemical analysis result of the solvable zirconium content in the sample of taking from all this three alloys tests.

Soluble and total zirconium content (%) of the sample that table 2 obtains by wet chemical analysis

^*Soluble: 15%HCl ^*Total: 50%HCl+6%RF

As finding, after 30 minutes stirred, soluble zirconium content had all reached 0.56% under 730 ℃ and 800 ℃ of these two temperature.This is in close proximity to the solubility limit of zirconium in melted pure magnesium, that is: 0.6 weight %.Report: the soluble zirconium content that obtains by the zirconium that is added same amount by the Zirmax mother alloy is generally less than 0.5%, and typically is about 0.4% under 720 ℃.(referring to: Y.Tamura, N.Kono, T.Motegi and E.Sato, " the grain refining mechanism and the cast structure of Mg-Zr alloy ", Japanese light metal association periodical, 1998, volume 48, No.4,185-189 page or leaf).The application of pretreated zirconium sponge is compared with the application of Zirmax mother alloy, demonstrates the better rate of recovery.

The stability of the zirconium sponge of handling

0.4%HF solution is to make by the 10%HF of 40ml is joined in the 960ml water.Be same as the zirconium sponge that is used for simultaneous test at room temperature immerse 0.4%HF 5 minutes, in water, clean and dry then.The zirconium sponge that this exsiccant was handled is kept in the plastics bag.

After four week of storage, the zirconium sponge particle that should handle 300g joins in the pure magnesium of 30kg under 680 ℃ and stirring.After 30 minutes stir and after stirring in 60 minutes, the zirconium sponge particle of handling is cast into chill bar sample (diameter is 25mm) before adding.

After stirring 30 minutes, obtained good grain refining.After stirring 30 minutes, soluble and total zirconium content is respectively 0.38% and 0.69%, and after stirring 60 minutes, it is increased to 0.42% and 0.81% respectively.

The preparation of magnesium-zirconium mother alloy

150g, size range join under 730 ℃ in the 550g magnesium melt for the zirconium sponge particle of the processing of about 1-3mm altogether.The nominal add-on of zirconium is about 25wt%.Add these zirconium particles in two batches.Run through whole alloying process stirs always.After stirring 60 minutes, this melt is cast in the steel ingot mould.

Fig. 7 and 8 has shown the microstructural representative view of the zirconium sponge of handling.Because the dissolving gradually of vesicular structure, each zirconium sponge particle will finally be decomposed into the many tiny zirconium particle of the about 2-3 μ m of size.Keep mild stirring to promote the generation of tiny zirconium particle suspension liquid in the melt always.

Can will be cast in the different moulds, preferably be cast in the chill mould as the above-mentioned magnesium that makes-zirconium melt.The aspect ratio 500mm of preferred each blank is not quite a lot, unless applied mould has excellent chill effect.If possible, preferred low casting temp is as 680 ℃ or lower.In casting cycle, must use blanketing gas.

Figure 10 and 11 expressions according to the above description, be added with 25% zirconium and the microstructural representative view of the blank that makes.White is the zirconium particle mutually.Figure 12 and 13 has represented the representative view of the Zirmax mother alloy of MEL.Just as can be seen, the zirconium particle that exists in mother alloy of the present invention is usually less than being present among the Zirmax.As previous argumentation, little zirconium particle is always highly preferred.

By 700 ℃, manual slowly the stirring under 90 minutes simultaneously, the zirconium sponge particle that 440g was handled joins in the 440g molten magnesium and the magnesium that contains the 50wt% zirconium of the having an appointment-zirconium mother alloy that makes.Figure 14 and 15 is for stirring the microstructural representative view of the blank of casting after finishing, and wherein grizzled particle is a zirconium, white be magnesium mutually.

Prepare magnesium-zirconium alloying from magnesium-zirconium mother alloy

The magnesium that contains the 25wt% zirconium of having an appointment-zirconium mother alloy (making according to the present invention) is joined in the crucible that contains the 30kg molten magnesium under 730 ℃.This mother alloy of preheating is to about 175 ℃ before in joining crucible, and adds the add-on of enough mother alloys with the zirconium that provides about 1wt%.

After adding mother alloy, stirred this melt 5 minutes with 150rpm with mechanical stirrer.Thereafter, this melt can be placed 15 minutes, cast the thick tabular sample of 30mm (160mm * 140mm) at 730 ℃ of following sand then.Before adding mother alloy, also cast the tabular sample of pure magnesium at 730 ℃ of following sand.The median size of the tabular sample of this pure magnesium is about 10,000 μ m.After being melt into alloy with mother alloy, the median size of prepared tabular sample is 98 μ m, soluble zirconium content be 0.49% and total zirconium content be 0.58%.

Be appreciated that in this manual the term that uses " comprise (comprise) " with and such as the modification of " comprising (comprises) " and " comprising (comprising) ", unless context needs, otherwise this application is to be used for hinting comprising described technical characterictic, and is not used in the existence of getting rid of other technical characterictic.

To the reference of any prior art be not in this manual and also should be considered to: this prior art is local in Australia or other, forms the understanding or any type of suggestion of the part of common practise.

Claims

1. magnesium-zirconium mother alloy, it contains does not have the dissolving of halide impurities zirconium and zirconium particle basically, and wherein 90% zirconium particulate size is less than 5 μ m.

2. one kind according to the described magnesium of claim 1-zirconium mother alloy, and it contains 10-50 weight % zirconium.

3. one kind according to the described magnesium of claim 1-zirconium mother alloy, and it contains 20-40 weight % zirconium.

4. one kind according to each described magnesium-zirconium mother alloy of aforementioned claim, and wherein 90% zirconium particulate size is less than 3 μ m.

5. one kind according to the described magnesium of claim 1-zirconium mother alloy, and it is by the method preparation that may further comprise the steps:

(a) (i) comprised the zirconium particle cluster, and have a kind of zirconium sponge that is coated to the top layer of fewer particulate fluorochemicalss to small part that contains and mix to form a kind of containing with (ii) molten magnesium and dissolve zirconium and zirconium particulate magnesium-zirconium melt; With

6. according to the described magnesium of claim 5-zirconium mother alloy, wherein fluorochemicals is the compound of Zirconium tetrafluoride.

7. according to the described magnesium of claim 6-zirconium mother alloy, wherein the chemical formula of the compound of Zirconium tetrafluoride is Zr _xF _yNH ₂O and x, y and n are integer.

8. one kind is added zirconium in the molten magnesium method as alloying element, and this method comprises: mixing with molten magnesium according to each described magnesium-zirconium mother alloy of aforementioned claim.

9. zirconic magnesium alloy that makes in accordance with the method for claim 8.