阅读说明：本技术 制造晶态铝铁硅合金的方法 (The method for manufacturing crystalline state ferro-aluminum silicon alloy ) 是由 Z·刘 齐腾蛟 J·R·萨尔瓦多 R·S·库克雷亚 于 2019-05-08 设计创作，主要内容包括：本发明提供了一种制造晶态铝铁硅合金以及任选的包含所述合金的汽车部件的方法,其包括通过在惰性环境中熔化铝、铁和硅原料形成基本上均匀的熔体,随后固化熔体形成包含多个晶相的复合锭,并通过在850℃至1000℃的温度下加热在真空下退火铸锭,得到退火的晶锭,其中主要的晶相是FCC Al<Sub>3</Sub>Fe<Sub>2</Sub>Si。原料可进一步包括一种或多种添加剂,例如锌、锆、锡和铬。熔化可以发生在FCC Al<Sub>3</Sub>Fe<Sub>2</Sub>Si晶相熔点之上,或在约1100℃至约1400℃的温度下。退火可以发生在真空条件下。(The present invention provides a kind of methods of manufacture crystalline state ferro-aluminum silicon alloy and the optional automobile component comprising the alloy, it include by inert environments melting aluminum, iron and silicon raw material form substantially uniform melt, it is subsequently cured the composite ingot that melt composition includes multiple crystal phases, and by 850 DEG C to 1000 DEG C at a temperature of heat ingot casting of annealing under vacuum, the crystal ingot annealed, wherein main crystal phase is FCC Al 3 Fe 2 Si.Raw material can further comprise one or more additives, such as zinc, zirconium, tin and chromium.Fusing can occur in FCC Al 3 Fe 2 On Si crystal phase fusing point, or about 1100 DEG C to about 1400 DEG C at a temperature of.Annealing can occur under vacuum conditions.)

1. a kind of method for manufacturing crystalline state ferro-aluminum silicon alloy, which comprises

By in inert environments melting aluminum, iron and silicon raw material to form substantially uniform melt and be subsequently cured described molten Body forms the composite ingot comprising multiple crystal phases；With

By 850 DEG C to 1000 DEG C ranges at a temperature of heat, crystal ingot of the ingot to be annealed of annealing under vacuum, In main crystal phase be FCC Al₃Fe₂Si。

2. a kind of method for manufacturing crystalline state ferro-aluminum silicon alloy, which comprises

By at least about 1050 DEG C at a temperature of melting aluminum, iron and silicon raw material and be subsequently cured melt, being formed includes multiple crystalline substances The composite ingot of phase；With

By be up to about 1000 DEG C at a temperature of heat come crystal ingot of the ingot to be annealed of annealing, wherein at least about 90% Annealing crystal ingot include FCC Al₃Fe₂Si crystal phase.

3. a kind of method for manufacturing automobile component, which comprises

By about 1100 DEG C to about 1400 DEG C at a temperature of melting aluminum, iron and silicon raw material and be subsequently cured molten in inert environments Body forms the composite ingot comprising multiple crystal phases；With

By 850 DEG C to 1000 DEG C ranges at a temperature of heat, under the vacuum of the pressure below about 60 millitorrs described in annealing Ingot and the then cooling crystal ingot to be annealed, the crystal ingot of wherein at least about 90% annealing include FCC Al₃Fe₂Si crystal phase.

4. method according to any one of the preceding claims, wherein fusing is comprising being heated to about 1100 DEG C to about 1400 DEG C Temperature.

5. method according to any one of the preceding claims, wherein fusing is comprising being heated above the FCC Al₃Fe₂The temperature of Si crystal phase fusing point.

6. method according to any one of the preceding claims, wherein annealing occurs in the true of the pressure below about 60 millitorrs Under sky.

7. method according to any one of the preceding claims, wherein the composite ingot includes the FCC less than about 0.01% Al₃Fe₂Si crystal phase.

8. method according to any one of the preceding claims, wherein the crystal ingot of the annealing includes three less than about 1% Oblique Al-Fe-Si crystal phase and six side's Al-Fe-Si crystal phases less than about 5%.

9. method according to any one of the preceding claims, wherein the melt includes the aluminium of about 31% to about 35%, The silicon of the iron of about 50% to about 55% and about 11% to about 13%.

10. method according to any one of the preceding claims, wherein the crystal ingot of the annealing includes non-less than about 1% Crystalline phase material.

Summary of the invention

There is provided a kind of method for manufacturing crystalline state ferro-aluminum silicon alloy, and including by the melting aluminum in inert environments, iron and Silicon raw material forms the composite ingot comprising multiple crystal phases to form substantially uniform melt and be subsequently cured melt, and by Ingot casting of annealing under vacuum is heated at a temperature of 850 DEG C to 1000 DEG C, the crystal ingot annealed.The principal crystalline phase of the crystal ingot of annealing It is FCC Al₃Fe₂Si.Fusing can include heating to about 1100 DEG C to about 1400 DEG C of temperature.Fusing, which can include heating to, to be higher than FCC Al₃Fe₂The temperature of Si crystal phase fusing point.Substantially inert environments may include argon atmosphere.Already solidified melt may include in inertia ring Cooling melt is at least about 1050 DEG C in border.Annealing can occur under the vacuum of the pressure below about 60 millitorrs.Composite ingot can FCC Al comprising being less than about 0.01%₃Fe₂Si crystal phase.The crystal ingot of annealing may include the three oblique Al-Fe-Si crystal phases less than about 1% With the six side's Al-Fe-Si crystal phases for being less than about 5%.The crystal ingot of at least about 90% annealing may include crystalline state FCC Al₃Fe₂Si phase. The ingot of annealing may include the amorphous phase material less than about 1%.This method can further comprise grinding composite ingot before the anneal.It should Melt may include the aluminium of about 31% to about 35%, the silicon of the iron of about 50% to about 55% and about 11% to about 13%.

A kind of method manufacturing crystalline state ferro-aluminum silicon alloy is provided.This method include by least about 1050 DEG C at a temperature of Melting aluminum, iron and silicon raw material are simultaneously subsequently cured melt to form the composite ingot comprising multiple crystal phases, and finally by rising to The crystal ingot for making ingot casting be annealed is heated at a temperature of about 1000 DEG C.The crystal ingot of at least about 90% annealing includes FCC Al₃Fe₂Si crystal phase.Fusing can occur in inert environments.Melt may include the aluminium of about 31% to about 35%, and about 50% to about The silicon of 55% iron and about 11% to about 13%.Annealing can occur under the vacuum of the pressure below about 60 millitorrs.Composite ingot It may include the FCC Al less than about 0.01%₃Fe₂Si crystal phase.

A kind of method manufacturing automobile component is provided.This method include by about 1100 DEG C to about 1400 DEG C at a temperature of The melting aluminum in inert environments, iron and silicon raw material are simultaneously subsequently cured composite ingot of the melt composition comprising multiple crystal phases, and finally lead to Cross 850 DEG C to 1000 DEG C at a temperature of heat, anneal ingot casting under the vacuum pressure below about 60 millitorrs, and then cool down The crystal ingot annealed.The crystal ingot of at least about 90% annealing includes FCC Al₃Fe₂Si crystal phase.Composite ingot may include being less than about 0.01% FCC Al₃Fe₂Si crystal phase.Melt may include the aluminium of about 31% to about 35%, the iron peace treaty of about 50% to about 55% The silicon of 11% to about 13%.

According to the detailed description of following exemplary embodiment and attached drawing, the other purposes of exemplary embodiment, advantage and new Clever feature will be apparent.

Detailed description of the invention

Fig. 1 shows the X-ray diffraction pattern of the melting composite ingot according to one or more embodiments；With

Fig. 2 shows the X-ray diffraction patterns according to the crystal ingot of the annealing of one or more embodiments.

Specific embodiment

Aluminium, iron and silicon are the materials of relative abundance.Theoretically, iron aluminide is (for example, quasi-equilibrium cube Al_xFe_ySi_zThree First phase) under the density close to titanium (for example, be less than 5g/cm³) there is extreme nature, but cost an order of magnitude lower than titanium.Example Such as, cube Al_xFe_ySi_zMutually there is excellent rigidity, elevated temperature strength, ductility is (for example, at least 5 slidings in crystal structure , wherein there are 12 slip systems in system, and have up to 48 cunnings in body-centered cubic (BCC) system in face-centered cubic (FCC) structure Move system) and tensile strength (for example, more than or equal to 450MPa) at room temperature.Since there are a large amount of aluminium, these mutually also have height Inoxidizability.

Without using expensive dusty material mechanical alloying and/or other energy-intensive techniques, it is difficult to Manufacture has main FCC Al₃Fe₂The Al-Fe-Si alloy of Si crystal phase.Melting disclosed by the invention and method for annealing can be used for making Making has mainly comprising FCC Al₃Fe₂The crystalline state ferro-aluminum silicon alloy of the expected micro-structure of Si crystal phase.In addition, presently disclosed molten Change and annealing heat-treatment method can be used in combination with one or more powder metallurgical techniques, to manufacture the crystal ferro-aluminum silicon of forming Alloy component.

As used herein, term " ferro-aluminum silicon alloy " or " Al-Fe-Si alloy " refer to comprising aluminium (Al), iron (Fe) and silicon (Si) material.Al-Fe-Si alloy also may include one or more additives comprising zinc (Zn), chromium (Cr), zirconium (Zr) and Boron (B) etc..The desired product of significant specific Al-Fe-Si alloy and all published methods is FCC between metal herein Al₃Fe₂Si crystal phase, it is characterised in that lattice parameter a=b=c=1.0806nm, battery parameterFor 10.806 (2), Fd-3m Space group, NiTi₂Structural type and cF96Pearson symbol.Although being named as Al for the sake of simplicity₃Fe₂Si, it should be understood that FCC Al₃Fe₂Si phase may show small deviation in composition.For example, for FCC phase Al_xFe_ySi_z, x can be equal to about 2.99 to About 3 and y can be equal to about 1.99 to about 2.25, so that z is normalized to be equal to 1.In other words, FCC phase Al₃Fe₂Si can wrap Containing about 48 atom % (" at.% ") to the Al of about 50at.%, the Fe of about 33.3at.% to about 36at.%, and about 16at.% is extremely The Si of about 16.7at.%.Unless stated otherwise, otherwise percentage (" % ") refers to weight percent.

There is provided herein melting and method for annealing, production display FCC Al₃Fe₂The Al-Fe-Si alloy of Si crystal phase is made For main the smallest amorphous phase mutually and if any, or not expected crystal phase, such as hexagonal phase or three oblique crystal phases.Make For the FCC Al of the main phase in crystalline state Al-Fe-Si alloy₃Fe₂The formation of Si crystal phase, and its preservation at room temperature, Ke Yifu Give the certain expected performances of crystalline state Al-Fe-Si alloy.For example, with Al-Fe-Si alloy or other crystal phases (that is, non-FCC Al₃Fe₂Si crystal phase) it accounts for leading part amorphous Al-Fe-Si alloy and compares, which may be relatively light, can express at high temperature Excellent mechanical strength out, high antioxidant and relatively high rigidity and ductility.As used herein, about Al-Fe-Si alloy In specific phase, term " main " and its various word forms and conjugation mean it is this be mutually in Al-Fe-Si alloy by weight Single maximum phase is counted, the weight fraction of main phase is greater than the weight of every other phase in Al-Fe-Si alloy in Al-Fe-Si alloy Score is measured, is used alone or in combination.

This method includes melting aluminum, iron and silicon raw material, and optionally one or more additives as described below first Material.One or more starting materials can be ball, the forms such as piece or powder.Advantageously, raw material can be mentioned with non-powder type For to avoid the cost of powder raw material.Aluminum feedstock purity can be usually that can get and close down to 95%, but 99% fine aluminium raw material Suitable.For example, aluminum feedstock may include aluminum shot, purity is about 99% to about 99.99% and diameter about 5mm to about 20mm.Iron is former Expect that purity can be usually available and suitable down to 95%, but 97% pure iron raw material.For example, it is about that iron material, which may include purity, The piece of 99% to about 99.99% is (for example, length and width is about 5mm to about 40mm, and with a thickness of about 1mm to about 10mm). Silicon raw material purity can be usually available and suitable down to the aluminum feedstock of 95%, but 99.9% purity.For example, silicon raw material can wrap The silicon ball or fragment that purity is about 99.9% are included, and there are various sizes.

The respective amount of Al, Fe and Si forms expected crystalline substance to be supplied to alloy during manufacture in selection Al-Fe-Si alloy The ability of body structure.Particularly, the respective amount of Al, Fe and Si in Al-Fe-Si alloy is selected to be supplied to alloy to form main packet The Al of phase containing FCC₃Fe₂The ability of the crystal structure of Si.It has been found that in practice, FCC in crystalline state Al-Fe-Si alloy Al₃Fe₂Aluminium in Si crystal phase, iron and the respective amount of silicon can be slightly different with the amount predicted by above-mentioned empirical formula.For example, molten Raw material in body can include about the aluminium of 31% to about 35%, the silicon of the iron of about 50% to about 55% and about 11% to about 13%.

As described below, Al-Fe-Si alloy optionally further comprises one or more additives, such as zinc, chromium, zirconium And/or boron etc..These additives can exist with the amount of about 3% to about 10% of alloy.Nevertheless, inadvertently introducing Additional elements in Al-Fe-Si alloy composite can be inherently present in alloy with relatively small amount, for example, with Al- The poidometer of Fe-Si alloy is less than 4.5%, and preferably smaller than 2.0%, and more preferably less than 0.02%.For example, these elements can To exist as the impurity in the raw material for being used to prepare Al-Fe-Si alloy composite.

In some embodiments, the composition of raw material can include about the aluminium of 34% to about 35%, the iron of about 53% to about 54% The silicon of about 11.5% to about 12.5%.In one suchembodiment, the composition of raw material can include about 34.5% aluminium, about 53.5% iron and about 12% silicon.

In some embodiments, the composition of raw material can include about the aluminium of 32.5% to about 33.5%, and about 52.25% to about 53.25% iron, the silicon of about 11.25% to about 12.25%, and the zinc of about 2% to about 3%.In one suchembodiment, The composition of raw material can include about 33% aluminium, about 52.7% iron, about 11.8% silicon and about 2.5% zinc.For example, due to packet Containing zirconium, this alloy can show increased crystalline state twin and improved ductility.

In some embodiments, the composition of raw material can include about the aluminium of 33% to about 34%, the iron of about 51% to about 52%, The silicon of about 11% to about 12%, the chromium of about 2.25% to about 3.25%, the zirconium of about 0.1% to about 0.4%, and at most about 0.1% Boron.In one suchembodiment, the composition of raw material can include about 33.4% aluminium, about 51.9% iron, about 11.6% Silicon, about 2.8% chromium, about 0.2% zinc and about 0.07% boron.For example, this alloy can show the crystal boundary of enhancing Refinement and improved ductility.

In some embodiments, the composition of raw material can include about the aluminium of 31.5% to about 32.5%, and about 50.5% to about 51.5% iron, the silicon of about 11% to about 12%, the zinc of about 2% to about 3%, the chromium of about 1.55% to about 3.25%, about 0.1% To about 0.4% zirconium, and at most about 0.1% boron.In one suchembodiment, the composition of raw material can include about 32% Aluminium, about 51.1% iron, about 11.4% silicon, about 2.4% zinc, about 2.7% chromium, about 0.2% zinc and about 0.07% Boron.For example, this alloy can show increased crystalline state twin, the crystal boundary refinement of enhancing and improved ductility.

In some embodiments, the composition of raw material can include about the aluminium of 32% to about 33%, and about 51.75% to about 52.75% iron, the silicon of about 11% to about 12%, and the zirconium of about 3% to about 4%.In one suchembodiment, raw material Composition can include about 32.6% aluminium, about 52.3% iron, about 11.7% silicon and about 3.4% zirconium.For example, due to comprising Zirconium, this alloy can show increased particle refinement.

In some embodiments, the composition of raw material can include about the aluminium of 32% to about 33%, and about 51.25% to about 53.25% iron, the silicon of about 11% to about 12%, and the tin of about 4% to about 5%.In one suchembodiment, raw material Composition can include about 32.3% aluminium, about 51.7% iron, about 11.6% silicon and about 4.4% tin.For example, due to comprising Tin, this alloy can show increased crystalline state twin.

In at least above FCC Al₃Fe₂Melt raw material is general uniform to be formed at a temperature of the fusing point (~1050 DEG C) of Si phase Melt.Fusion temperature keeps below the fusing point (~1538 DEG C) of iron and the fusing point (~1414 DEG C) of silicon, and is optionally below Except any additive, zinc and tin.Therefore, in some embodiments, in about 1050 DEG C of temperature, about 1100 DEG C to about 1400 DEG C At a temperature of melt raw material.The additive increased in Al-Fe-Si alloy may need higher fusion temperature.For example, raw material can To be melted in boron nitride crucible.Alternatively, raw material can melt in a mold, such as automobile component mold.Utilizing vapour In this embodiment of vehicle part mold etc., composite ingot includes automobile component.Raw material can melt in inert environments, to arrange Except not expected oxidation or mutually formed.For example, inert environments may include argon gas and/or neon atmosphere.

Then melt is solidified to form composite ingot.After the completion of fusing, melt can cool down in inert environments, until melt Solidification or substantially solidification (are typically FCC Al₃Fe₂Near the fusing point of Si phase), to minimize macroporosity.In some realities It applies in example, melt Slow cooling in inert environments, until reaching about 1100 DEG C down to about 1000 DEG C of temperature.Composite ingot can be with Environment temperature is cooled further under ambient atmospheric conditions.Before the anneal, composite ingot is optionally ground to partial size, Show the feature (for example, tap density and mobility) suitable for powder metallurgical technique.Grinding can use roller mill, ball mill Or other suitable methods carry out.For example, composite ingot can be ground to about 50 μm to about 500 μm of partial size.

Composite ingot may include one or more crystal phases, and optional one or more amorphous phases.For example, composite ingot may include Fe_1.7Al₄Six side of Si (P63/mmc) crystal phase, Fe₃Al_0.25Si_0.75Cube (Fm-3m)

Crystal phase and Fe₃Al cubes of (Pm-3m) crystal phase.Therefore, may exist one or more non-Al-Fe-Si crystal phase (examples Such as, Fe₃Al cubes of (Pm-3m) crystal phase).In some embodiments, composite ingot may include the FCC Al less than about 0.01%₃Fe₂Si Crystal phase, or substantially free of FCC Al₃Fe₂Si crystal phase.

Then it is being lower than FCC Al₃Fe₂It anneals at a temperature of the fusing point of Si crystal phase to composite ingot, with the crystal ingot annealed. The crystal ingot annealed, wherein FCC Al₃Fe₂Si crystal phase is main crystal phase.In addition, the crystal ingot of annealing includes considerably less Or it there is no amorphous phase or low symmetrical crystal phase, such as three oblique Al-Fe-Si are (for example, Al₃Fe₂Si) crystal phase.In some implementations Example in, at least about 80%, at least about 85% or at least about 90% annealing crystal ingot include crystalline state FCC Al₃Fe₂Si phase.In addition Or alternatively, in some embodiments, the crystal ingot of annealing includes the amorphous phase material less than about 1%.Additionally or alternatively, In some embodiments, the crystal ingot of annealing includes the three oblique Al-Fe-Si crystal phases less than about 1%.Additionally or alternatively, one In a little embodiments, the crystal ingot of annealing is comprising the six side Al-Fe-Si less than about 5% (for example, Al₃Fe₂Si) crystal phase.

Annealing occurs at a temperature of at least about 800 DEG C, at least about 825 DEG C or at least about 850 DEG C.In some embodiments In, annealing occurs at a temperature of about 850 DEG C to about 950 DEG C, or about 850 DEG C to about 1000 DEG C.Improving annealing temperature can subtract Few annealing time can be optimized for specific alloying component.Composite ingot can anneal a period of time, appropriate landform At the FCC Al of desired amount₃Fe₂Si crystal phase.In some embodiments, composite ingot can anneal about 2 hours to about 24 hours.

Annealing can carry out in vacuum environment and/or inert environments.In some embodiments, annealing occurs in high vacuum Under." high vacuum " condition may include about 60 millitorrs to about 0.001 millitorr, or more preferably about 6 millitorrs are to about 0.001 millitorr.Very Altitude may be implemented and inert environments (for example, ar gas environment) identical purpose, but for being added comprising relative volatility The alloy (such as zinc) of agent is less applicable in.In some embodiments, annealing occurs in argon atmosphere.In some embodiments, Annealing occurs in vacuum and argon atmosphere.In some embodiments, annealing occurs in N₂In atmosphere, such as wherein in composite ingot Upper formation nitride layer is expected.After annealing, the crystal ingot of annealing can be cooled down.

Stable FCC Al₃Fe₂The quality of Si crystal phase alloy make they be suitable for automobile or other vehicles (such as motorcycle, Ship) component.For example, stable FCC Al₃Fe₂Si crystal phase alloy is applicable to be formed lighter engine valve or other are light Matter valve, in order to form light piston, in order to form rotation and the reciprocating part of internal combustion engine, and/or in order to be used for turbocharging Device application (for example, forming turbocharging device wheel).Stable FCC Al₃Fe₂Si crystal phase alloy can also be used for it is various other industry and Using including aerospace components, industrial equipment and machinery, farm equipment and/or heavy-duty machinery as non-limiting examples.One In a little embodiments, component can form expected shape during melting step.Alternatively, the crystal ingot of annealing then can be used Any suitable technology forming member (for example, automobile component), for example, rolling, forging, punching press, powder metallurgy or casting (for example, Die casting, sand casting, permanent molding etc.) etc..

Example

It combines aluminium, iron and silicon raw material to form the 400g melt comprising 35% aluminium, 53% iron and 12% silicon.Raw material is existed It is melted 5 minutes at 1200 DEG C, to form diameter about 3.8cm, the cylindrical composite ingot of high 7.7cm.Using copper K α radiation X-ray diffraction is carried out to gained composite ingot using D8-Advance Davinci diffractometer in Bragg Brentano configuration (XRD).Data are collected from 10 ° of -90 ° of 2 θ using the time of integration of 0.02 ° of step-length and 1 second/step.Use DIFFRAC.SUITE TOPAS software carries out Rietveld refine.Fig. 1 shows the XRD diagram case of prepared composite ingot.Prepared composite ingot XRD diagram case shows about Fe_1.7Al₄Six side of Si (P63/mmc) crystal phase (by the triangle expression in Fig. 1), about 23% Fe₃A_l0.25Si_0.75Cube (Fm-3m) crystal phase (indicates) by the circle in Fig. 1, about 5%Fe₃Al cubes of (Pm-3m) crystal phase is (by Fig. 1 In star indicate) and unrecognizable phase (by Fig. 1 square expression) form.

Composite ingot is then annealed to 24 hours under the vacuum of 0.01 millitorr at 950 DEG C to form the crystal ingot annealed.In D8-Advance Davinci diffractometer is used to carry out gained crystal ingot using in the Bragg Brentano configuration of copper K α radiation XRD.Data are collected from 10 ° of -90 ° of 2 θ using the time of integration of 0.02 ° of step-length and 1 second/step.Use DIFFRAC.SUITE TOPAS software carries out Rietveld refine.Fig. 2 shows the XRD diagram cases of the crystal ingot of prepared annealing.Prepared crystal ingot XRD diagram case shows about 92%Fe₂Al₃Si FCC (Fd-3m) crystal phase (by the triangle expression in Fig. 2), about 5% Fe₃Al_0.25Si_0.75FCC (Fm-3m) crystal phase (being indicated by the circle in Fig. 2) and about 3%Fe₂₃Al₈1Si₁₅Hexagonal(P63/ Mmc) crystal phase (by Fig. 2 asterisk indicate) form.These results indicate that without using powder raw material or mechanical alloying In the case of, a large amount of FCC Fe can be used₂Al₃Si crystalline formation crystal ingot or automobile component.It only anneals under similar conditions about 8 hours It can be obtained similar result.

Although it is encompassed in the claims to be not meant to that these embodiments describe the foregoing describe exemplary embodiment All possible forms.Word used in specification is descriptive words rather than restricted word, and should understand that It is that various changes can be carried out without departing substantially from spirit and scope of the present disclosure.As previously mentioned, the spy of various embodiments Sign can be combined to form the further embodiment of the present invention that may be not explicitly described or shown.Although various embodiments can be with Offer advantage is provided or is realized in the expected characteristic aspect of one or more better than other embodiments or the prior art, this field Those of ordinary skill, which recognizes, can trade off one or more characteristics or feature to realize expected total system attribute, depend on In specific application and realize.These attributes may include but be not limited to cost, intensity, durability, and life cycle cost can be sold Property, appearance, packaging, size is maintainable, and weight, manufacturability is easily assembled to.Therefore, in terms of one or more features Not satisfactory described embodiment is realized not outside the scope of the present disclosure than other embodiments or the prior art, and right It may be desired in specific application.