高压扭转处理后铝铁界面微观组织及性能研究

Interfacial microstructures and properties of aluminumalloys/galvanized low-carbon steel under high-pressuretorsionYang Liu a ,Xiufang Bian a ,⇑,Kai Zhang a ,Chuncheng Yang a ,Le Feng a ,Hyoung Seop Kim b ,Jing Guo b ,caKey Laboratory for Liquid-solid Structural Evolution and Processing of Materials,Ministry of Education,Shandong University,Jinan 250061,PR China bDepartment of Materials Science and Engineering,Pohang University of Science and Technology,Pohang 790-784,South Korea cCollege of Mechanical and Electronic Engineering,Shandong Agricultural University,Taian 271018,PR Chinaa r t i c l e i n f o Article history:Received 5May 2014Accepted 24July 2014Available online 8August 2014Keywords:Aluminum alloys Low-carbon steel Hot-dipping InterfaceHigh pressure torsiona b s t r a c tA new composite processing technology characterized by hot-dip Zn–Al alloy process was developed to achieve a sound metallurgical bonding between Al–7wt%Si alloy (or pure Al)castings and low-carbon steel inserts,and the variations of microstructure and property of the bonding zone were investigated under high-pressure torsion (HPT).During hot-dipping in a Zn–2.2wt%Al alloy bath,a thick Al 5Fe 2Zn x phase layer was formed on the steel surface and retarded the formation of Fe–Zn compound layers,resulting in the formation of a dispersed Al 3FeZn x phase in zinc coating.During the composite casting process,complex interface reactions were observed for the Al–Fe–Si–Zn (or Al–Fe–Zn)phases formation in the interfacial bonding zone of Al–Si alloy (or Al)/galvanized steel reaction couple.In addition,the results show that the HPT process generates a number of cracks in the Al–Fe phase layers (consisting of Al 5Fe 2and Al 3Fe phases)of the Al/aluminized steel interface.Unexpectedly,the Al/galvanized steel interface zone shows a good plastic property.Beside the Al/galvanized steel interface zone,the microhardnesses of both the interface zone and substrates increased after the HPT process.Ó2014Elsevier Ltd.All rights reserved.1.IntroductionAluminum alloys and steels are indispensable engineering materials because they have good mechanical properties and rela-tively low material costs in many applications [1].As a result of more stringent requirements for improved fuel economy and emissions,there is a growing trend to substitute light alloy for con-ventional steel or cast iron in the automotive industry [2].Bimetal-lic composites consisting of light alloys and steels/cast iron can meet the need for high strength and reduce weight to improve fuel economy and emissions,so they possess a great potential for future developments in automotive technology [3–5].In order to produce a bimetallic composite with good mechan-ical properties,several composite casting techniques have been applied.The chemical reaction is difficultly triggered between Al and iron when pure Al melt is directly poured to surround the iron insert without pretreatment [6].Viala et al.[7,8]manufactured bimetallic automotive components consisting of light alloys and cast iron by using the combination of Al-Fin process and gravity casting.Bouayad et al.[9]produced such bimetallic composites using high pressure die casting.The crucial point in the composite casting techniques is the liquid/solid interface between light alloys and ferrous metals substrate.A good wettability of solid substrates is essential in achieving good metallurgical bonding at the inter-face.In order to improve the wettability of solid substrates,an interlayer coated on the substrate surface has been a common approach.The Al-Fin process is a method of coating Al alloys on the sur-face of ferrous metals by hot-dipping [7].The Al-Fin bond is a bond between an Al alloy and a ferrous metal.The effect of hot-dipping bath composition on the morphology of the interfacial bonding zone is important.The addition of Silicon into the Al alloy bath has a significant influence on the continuous intermediate layer,which not only produces flat morphology from the classical ton-gue-shaped one in the interface between the intermediate layer and the steel substrate,but also affects the growth of the interme-diate layer [10–12].In the liquid/solid diffusion couple,Si deceler-ates the growth of g phase in the intermediate layer.In contrast,Springer et al.[13]presented that Si can accelerate the growth of g phase in the intermediate layer for the solid/semisolid diffusion couples.The effect of Mn on the interface has also been studied.Choi et al.[14]found that additional content Mn can make the thickness of the intermetallic layer increase comparing to the Al alloy without Mn at the interface between a low Si Al alloy and STD61steel.Our previous work [15]has also demonstrated that/10.1016/j.matdes.2014.07.0530261-3069/Ó2014Elsevier Ltd.All rights reserved.⇑Corresponding author.Tel.:+8653188392748;fax:+8653188395011.E-mail address:xfbian@ (X.Bian).the addition of Mn facilitated the formationa-Al15(Fe x Mn1Àx)3Si2phases and the growthmetallurgical bonding layer at the Al–7wt%which can improve the properties of the Al/FeOn the other hand,there are manyalloys can also serve as a good interlayerjoint of dissimilar metals[16–19].Variousinvestigated for coating the zinc or zinc alloysurface of the base metal,such asplating[17],and hot-dipping[18,19].The zinclayer can not only protect the base metal fromimprove the wettability of the base metal.environment and conditions for interfacesimilar metals.Zinc coating on steel is alsoapplications especially in the automotivecorrosion resistance of steel used for carmany studies have been reported to join Al alloy to zinc-basedcoated steel by laser welding-brazing(LWB),friction stir welding (FSW),cold metal transfer(CMT),laser-tungsten inert gas(TIG) hybrid welding,etc.[21–25],but very little work has been done on the composite casting.How to achieve an excellent metallurgi-cal bonding between Al alloys and low-carbon steel still is quite a challenging subject.In this study a new composite processing technology character-ized by an auxiliary hot-dip Zn–Al alloy process was developed in order to achieve a sound metallurgical bonding between Al alloy or pure Al and low-carbon steel.In order to extent the application sphere of the Al/steel bimetal composite under high pressure envi-ronment,the variations of microstructure and properties were investigated for the Al/aluminized steel and the Al/galvanized steel samples after high-pressure torsion(HPT)process.2.Experimental procedureSteel samples(diameter3mmÂlength100mm)were cut out from a low-carbon steel bar(containing0.06–0.12wt%C)coated a pure zinc coating by electroplating.Prior to immersing the sam-ples in liquid Zn–2.2wt%Al bath at723±10K for various time,all the surface of the steel samples were polished in order to remove surface ZnO layers and cleaned in ethanol.The thickness of the electroplated zinc coating was approximately5l m after polishing. Then,the hot-dip galvanized steel samples were moved away from the liquid Zn–Al bath and fastened rapidly on a permanent mould preheated at473K,respectively.Si,0.3–0.45wt.%Mg,0.2wt.%Ti, and Al)was poured into the mould at993±10K.These liquid Zn–Al alloy,Al and Al–Si alloy were melted in an intermediate fre-quency furnace and held at a setting temperature in a resistance furnace.The Al/steel samples were cut into small disks(diameter 10Âlength1.5mm)for the HPT process.These small disks were placed in a circular shallow hole of the lower HPT anvil,as shown in Fig.1[26].Then,the lower anvil with the disk sample was raised to contact the upper anvil having the same shallow hole at the cen-ter.While applying a pressure of5GPa at room temperature,the lower anvil was rotated at a rotation speed of1rpm and the rota-tion was terminated after1turn.In order to evaluate the effect of the HPT process on the strength of the bonding interface,the Vick-ers micro-hardness test(model DHV-1000)was performed along the thickness direction of the original and treated samples with a low indentation load of10g.For the composition and microstructure analyses,vertical or horizontal cross sections were prepared by successive grinding and polishing.The vertical and horizontal cross section samples were cut from the Al–Si alloy or Al/galvanized steel composite and mounted using epoxy by a mounting press.In order to further analyze the interfacial bonding zone,the interfacial microstructure of each sample was examined using an optical microscope(OM) and scanning electron microscopy(SEM).The phases were chemi-cally characterized to evaluate the nature of the intermetallics using energy dispersive spectroscopy(EDS).3.Results3.1.Growth and microstructure of the hot-dip galvanized coatingThe hot-dip Zn–Al alloy process is a vital step for achieving a sound metallurgical bonding between Al alloy castings and steel inserts,so it is essential to study the growth and microstructure of the hot-dip galvanized coating.Fig.2exhibits SEM images of the vertical section of the steel sample after hot-dipping in Zn–2.2wt%Al melt at723K for300s and the thicknesses of the hot-dip galvanized coating and the dif-fusion layer as a function of hot-dip time.The average thickness of the light gray Zn–Al coating on the surface of the steel substrate is approximately292l m.The diffusion layer consisting of some dark gray phases was formed in the interface between the Zn–Al coating and steel substrate after hot-dipping.The dark gray phase exhibits continuously graded morphology and is strongly attached to the steel substrate.However,some pores exist in the region adjacent to the steel substrate.They are attributable to the steel particles dissolved from the steel substrate during hot-dipping and departed during grinding and polishing.The other parts of the dark gray phases exhibit dispersive distribution in the Zn–Al coating.The microstructure of the interface between the Zn–Al coating and steel substrate can be observed clearly in Fig.2(b).The chemical compositions of these interfacial phases were identified using spot scanning of SEM-EDS,as shown in Table1.According to the char-acterization of the ternary solid phase in Al–Fe–Zn system[27,28], the continuous layered phases were identified as Al5Fe2Zn x,and the dispersive phases were identified as Al3FeZn x.It can be seen that the average thickness of the hot-dip galvanized coating increases with increasing hot-dip time,and the average thickness of the diffusion layer presents the same trend(Fig.2(c)).3.2.Observation of the Al/galvanized steel and Al–Si/galvanized steel interfaces after pouringThe objective of this part is to analyse the effect of the different composition of the Al melts on the microstructure forming at the Al alloy casting/galvanized steel insert interface.Fig.3presents the optical micrographs of the Al–Si/galvanized steel and Al/galvanized steel interfaces obtained from the samples poured from Al–Si alloy and pure Al melts,respectively.TheFig.1.Schematic of the HPT process.288galvanized steel samples were obtained by hot-dipping the steel bar in Zn–2.2wt%Al bath at723K for300s.The layered microstructure was formed at the Al–Si/galvanized steel and Al/galvanized steel interfaces.A number of largedistributed in the Al substrate(Fig.3(b)).However,hardly any the large layered phases distributedsubstrate(Fig.3(a)).Fig.4shows the magnified SEM images ofsteel and Al–Si/galvanized steel interface obtainedpoured at993K and the linear scanning analysisThe chemical compositions of the Al–Si/galvanizedgalvanized steel samples obtained from hot-dipping in the Zn–2.2wt.%Al melt at723K for300s;(b)the magnified view of thicknesses of the hot-dip galvanized coating and the diffusion layer as a function of hot-dipping time.Table1analysis for the Zn–Al/steel interface using SEM-EDS from the(b).Compositions(at.%)PhaseFe Zn–90.18Zn23.028.44Al3FeZn x26.38 6.18Al5Fe2Zn x100–FeOptical micrographs of(a)Al–Si/galvanized steel and(b)Al/galvanized steel interfaces obtained from the sample poured atAl/galvanized steel interfacial phases were identified by spot scan-ning using SEM-EDS,as shown in Table 2.The Al–Si/galvanized steel interface consists of a continuous Al 5Fe 2Zn x phase layer,a continuous Al 8(Fe,Zn)2Si phase layer and a discontinuous needle-like Al 5(Fe,Zn)Si phase layer,as shown in Fig.4(a).These phases were identified using the analysis of linear scanning from Fig.4(b)and the result of spot scanning from Table 2using SEM-EDS.The Al/galvanized steel interface consists of a continuous Al 5Fe 2Zn x phase layer and some layered Al 3FeZn x phases,as shown in Fig.4(c).These phases were identified by the analysis of linear scanning from Fig.4(d)and the result of spot scanning from Table 2using SEM-EDS.3.3.Analysis of the Al/aluminized steel and Al/galvanized steel interfaces after HPTIn order to study the effect of high pressure on the Al casting/steel insert interface,the HPT process was performed on the Al–Si/aluminized steel and Al/aluminized steel samples.And meanwhile,the variation of microstructure and properties werealso investigated for the Al/aluminized steel and Al/aluminized steel interface after the HPT process.Fig.5shows the macro and enlarged SEM images of the samples after the HPT process.Fig.5(a)presents the sample hot-dipped in pure Al bath at 993K for 300s before pouring fresh pure Al at 993K,followed by HPT.A classical ‘‘tongue-like’’interface zone was found.The intermetallic compound layer is made up of Al 5Fe 2and Al 3Fe phases [12].The thickness of the samples decreased from 1.5mm to 0.9mm under the pressure of 5GPa at room tempera-ture.The Al/aluminized steel interface deformed to arc-shaped,as shown in Fig.5(a).The Al/galvanized steel interface has also severely deformed under the vertical load and horizontal torsion,as shown in Fig.5(b).This sample was hot-dipped in Zn–2.2wt%Al bath at 723K for 300s,followed by pouring fresh pure Al at 993K and HPT.The Al/galvanized steel interface formed a relatively thinner intermetallic compound layer (containing the Al 5Fe 2Zn x and Al 3FeZn x phases)than the Al/aluminized steel inter-face,which enhances plastic performance.According to the enlarged SEM images,there are a number of cracks in the intermetallic compound layer of the Al/aluminized steel interface after the HPT process (see Fig.5(c)).It is because the brittle Al 5Fe 2and Al 3Fe phases are hard to bear the pressure of 5GPa.In contrast,the relatively thinner Al 5Fe 2Zn x and Al 3FeZn x phase layers have a good plastic ductility to restrain the crack formation (see Fig.5(d)).However,the steel/compound and com-pound/Al interfaces have not been broken after the HPT process (see Fig.5(e)).The particle phases formed in the Al substrate are more homogeneously distributed after the HPT process.Its diame-ter is approximately 1l m (Fig.5(f)).The microhardnesses of the Al/aluminized steel and Al/galva-nized steel interfaces are shown in Fig.6both before and after the HPT process.Besides the intermetallic compound layer attheimages of the bonding interface obtained from pouring at 993K and the analysis of linear scanning:(a)Al–Si/galvanized steel;arrow in Fig.4(a);(c)Al/galvanized steel;(d)the analysis of linear scanning along the red arrow in Fig.4(c).(For interpretation legend,the reader is referred to the web version of this article.)Table 2Chemical analyses for the Al–Si/galvanized steel and Al/galvanized steel interfaces using SEM-EDS analysis from selected regions in Fig.4(a)and (c).Composition (at.%)PhaseAlFe Si Zn 168.2512.6016.22 2.93Al 5(Fe,Zn)Si 268.0819.0310.80 2.08Al 8(Fe,Zn)2Si 365.4324.660.948.97Al 5Fe 2Zn x 468.5524.90– 6.55Al 5Fe 2Zn x 575.2519.87–4.88Al 3FeZn xenlarged SEM images of the samples after the HPT process:(a),(c),(e)Al/aluminized steel and(b),(d),(f)Al/galvanized Fig.6.Microhardnesses of the interfaces of(a)Al/aluminized steel and(b)Al/galvanized steel both before and after the HPT process.Al/galvanized steel interface,the HPT process increased the microhardness of the Al/aluminized steel interfaces and substrates.4.DiscussionDissimilar metal composite casting is a powerful joining method that has a great relevance for industrial applications.A good wettability of the surface of steel substrates is essential in realizing this process.Wetting is a strong function for interfacial metallurgical reactions and can only be achieved by eliminating the natural oxide layer[17].Electrogalvanizing coating is generally applied in order to protect the surface of steel substrates from oxi-dation in air and improve the wettability of steel substrates.Also, the hot-dip galvanizing treatment makes possible a metallurgical reaction between liquid Al alloy and solid steel.These processes guarantee a good metallurgical bonding interface between Al alloy and steel.At the beginning of the hot-dip galvanizing step,the tempera-ture of the steel surface rapidly increases up to approximately 723K.The electrogalvanizing coating meltsfirstly,and then the liquid alloy very efficiently protects the steel from oxidation by air,hence no new zinc or steel oxide is developed at the Zn–Al alloy/steel interface.A metallurgical reaction occurs between the steel surface and Zn–Al alloy and the gradual diffusion of the free atoms into the steel substrate becomes possible.During hot-dipping at723K,both metallurgical reaction and dissolution simultaneously proceed at the Zn–Al alloy/steel inter-face.The formation of intermediate phases is a complex process. There mainly form Al5Fe2Zn x phase and Al3FeZn x phase at the interface between Zn–Al alloy and steel.The reaction process is described as follows.At the beginning,a number of Al atoms gather around the steel surface and diffuse into the steel substrate,which results in chemical reaction proceeding at the liquid–solid inter-face(for example,2Fe+5[Al]Zn+xZn?Al5Fe2Zn x)[28].This reac-tion rapidly induces the formation and growth of a continuous Al5Fe2Zn x phase layer on the steel surface,which inhibits the for-mation of Fe–Zn compound[29,30].According to Fig.2(b),a tenta-tive inference is that Al atoms diffuse from the Zn–Al bath to the steel substrate along grain boundaries to form Al5Fe2Zn x phase. With growing the Al5Fe2Zn x phase,then,some iron particles simul-taneously dissociates from the steel substrate and dissolve into Zn–Al bath.Meanwhile,the Al atoms gather around the free iron particles.According to the study of phase equilibrium in Ref.[31] and the Al–Fe–Zn isothermal section at723K[32],the Al3FeZn x phase can arise as a product of the following chemical reactions: 5½AlZnþ2FeþxZn!Al5Fe2Zn x;ð1Þ½AlZnþxZnþAl5Fe2Zn x!2Al3FeZn x:ð2ÞSome Zn atoms dissolve into the Al3Fe phase to form solid solution. At last,a number of dispersed Al3FeZn x phases are formed in the Zn–Al coating during solidifying.The growth of these compounds is controlled by a diffusion process of Al atoms and Fe atoms.It is similar to the growth of intermetallic compounds in Al–Fe system in Refs.[33,34].With increasing the hot-dip time,the thickness of the diffusion layer increased,as shown in Fig.2(c).The hot-dip pro-cess makes the steel preheat to723K and forms an Al–Fe phase layer at the Zn–Al alloy/steel interface,which is a vital step to form a metallurgical bonding interface.It is beneficial to fuse the Zn–Al coating on the surface of steel during subsequent pouring and improve the wetting of the steel surface by Al alloy melts.When the steel samples are moved from the Zn–Al bath to the mold,the Zn–Al alloy coating/steel substrate interface state rapidly changes.Therefore,a sufficiently fast transfer is required.Never-theless,a thin oxidation layer cannot be avoided on the surface of the hot-dip galvanized steel.When the fresh Al–Si alloy or pure Al is rapidly poured into the mould at993K,the oxidationfilm is not strong enough to withstand the impact by the liquidflowing onto it and then,the Zn–Al coating is remelted and dissolves in the liquid Al–Si alloy or pure Al.The diffusion layer also partly dis-solves in the liquid Al–Si alloy or pure Al.At the same time,the Fe content of the liquid Al–Si alloy or pure Al in the vicinity of the steel surface rapidly approaches saturation under the combined effects of thermodynamics and kinetics.With decreasing the pour-ing temperature,the maximum solubility of Fe in the alloy decreased[35].As a result,the intermetallic compound layer forms rapidly again and grows.The morphology of the intermetallic compound layer is shown in Fig.3.When the Al–Si alloy is poured,three intermetallic compounds,Al5(Fe,Zn)Si,Al8(Fe,Zn)2Si,and Al5Fe2Zn x,are formed (Fig.4(a)).Taking into account published or recently acquired data on the Al–Fe–Si system[7,36–38],the formation of the Al–Fe–Si phases during solidification in the interface zone can take place through the following reactions:LþAl3FeZn x!Al8ðFe;ZnÞ2SiþAlð3ÞL!Al8ðFe;ZnÞ2SiþAlð4ÞLþAl8ðFe;ZnÞ2Si!Al5ðFe;ZnÞSiþAlð5ÞL!Al5ðFe;ZnÞSiþAlþSið6ÞWhen the pure Al is poured,only Al5Fe2Zn x and Al3FeZn x phases are formed(Fig.4(c)).This is consistent with the interface of the hot-dip aluminized steel[13].In this process,the Zn–Al coating is also remelted during pouring,which promotes steel atoms and Al5Fe2 Zn x phase transferring to the Al melt.Consequently,some layered morphology forms at the Al/galvanized steel interface(see Fig.3).In general,the HPT process is used to provide grain refinement of hard-to-deform materials[39]or promote solid-state reactions [26].In this study,we tried to study the effects of high pressure on the microstructure and mechanical properties of the Al/steel interface by performing the HPT.So we investigated the variation of microstructure and properties for the Al/aluminized steel and Al/galvanized steel composite samples after the HPT process.The HPT process makes the Al/aluminized steel and Al/galvanized steel composite samples deform severely(see Fig.5).For the Al/alumi-nized steel interface,a number of cracks form in the thick interme-tallic compound layer after the HPT process(see Fig.5(c)).It is because Al5Fe2and Al3Fe phases are difficult to bear the pressure of5GPa,although the HPT process can improve the property of substrate by grain refinement.The HPT process improved the microhardness of substrate significantly(see Fig.6(a)).The HPT process severely deforms the Al/galvanized steel interface,but the interfacial microstructure is not broken(see Fig.5(d)and(f)). The abnormal deformation of steel insert may be due to the off-center positioning in the sample and torsion processing,as shown in Fig.5(b).In addition,the severe abnormal deformation also reflects a good plastic performance of the Al/galvanized steel inter-face.Fig.6(b)exhibits that both Al and steel substrates are strengthened after the HPT process.However,the hardness of the interfacial zone decreased.Meanwhile,a number of the particle phases are formed with homogeneous distribution in Al alloy sub-strate after the HPT process.Some particle phases may be formed from the fragmented needle phase after the HPT process.The oth-ers may be attributed to the severe plastic deformation which induced the solid solution of Fe atoms in Al substrate gathering and then transforming to Al–Fe particle phases.The new composite processing technology characterized by hot-dip Zn–Al alloy on the surface of low-carbon steel achieves a sound metallurgical bonding between the Al alloys and low-carbon steel.This composite fabrication approach has an important signif-icance and practical value for the development of liquid–solid composite materials.292Y.Liu et al./Materials and Design64(2014)287–2935.ConclusionsA hot-dip galvanizing treatment was applied in order to form a sound metallurgical bonding interface between pure Al or Al–Si alloy and low-carbon steel.In addition,the variations of micro-structure and properties were investigated for the Al/aluminized steel and Al/galvanized steel samples after the HPT process.The following conclusions were obtained.1)Electrogalvanized pure zinc coating can improve the wetta-bility of surface of the steel substrate.It enhances the forma-tion of a good metallurgical bonding layer at the interface between Zn–Al coating and steel substrate.With increasing hot-dip time,the average thickness of the diffusion layer consisting of Al5Fe2Zn x and Al3FeZn x phases increases.2)The hot-dip galvanizing treatment promotes the liquid–solidreaction between Al–Si alloy(or pure Al)and low-carbon steel during pouring Al–Si alloy(or pure Al),so that the Al5 (Fe,Zn)Si,Al8(Fe,Zn)2Si,and Al5Fe2Zn x(Al5Fe2Zn x and Al3Fe Zn x)intermetallic compounds were formed in the interface zones.3)The Al/galvanized steel interface has the better plastic prop-erty than Al/aluminized steel interface under high pressure environment.In addition,the HPT process strengthens the substrates of the Al–Si alloy(or pure Al)and steel. AcknowledgmentsThe authors are grateful for thefinancial support from the National Natural Science Foundation of China(Grant No. 51371107)and Scientific and Technological Project of Shandong Province(Grant No.2013GGX10217).Guo Jing was supported by the national research foundation of Korea through the Korea-China Young Scientist Exchange Program.References[1]Crane FAA,Charles JA,Furness J.Selection and use of engineeringmaterials.Butterworth-Heinemann;1997.[2]Cole GS,Sherman AM.Lightweight materials for automotive applications.Mater Charact1995;35:3–9.[3]Yang Y,Zhang XM,Li ZH,Li QY.Adiabatic shear band on the titanium side inthe Ti/mild steel explosive cladding interface.Acta Mater1996;44:561–5. [4]Sierra G,Peyre P,Deschaux Beaume F,Stuart D,Fras G.Galvanised steel toaluminium joining by laser and GTAW processes.Mater Charact2008;59: 1705–15.[5]Zhe M,Dezellus O,Gardiola B,Braccini M,Viala JC.Chemical changes at theinterface between low carbon steel and an Al–Si alloy during solution heat treatment.J Phase Equilib2011;32:486–97.[6]Li WZ,Bian XF.Metallographic study of interface achieved by aluminum–ironcompound casting.Chin J Mech Eng2011;47:67–72.[7]Viala JC,Peronnet M,Barbeau F,Bosselet F,Bouix J.Interface chemistry inaluminium alloy castings reinforced with iron base posites Part A 2002;33:1417–20.[8]Sacerdote-Peronnet M,Guiot E,Bosselet F,Dezellus O,Rouby D,Viala JC.Localreinforcement of magnesium base castings with mild steel inserts.Mater Sci Eng A2007;445:296–301.[9]Bouayad A,Gerometta C,Radouani M,Radouani M,Saka A.Interfacecharacterization in aluminum alloy casting reinforced with SG iron inserts.J Adv Res Mech Eng2010;1:226–31.[10]Cheng WJ,Wang CJ.Effect of silicon on the formation of intermetallic phases inaluminide coating on mild steel.Intermetallics2011;19:1455–60.[11]Pietrowski S,Szymczak T.Effect of silicon concentration in bath on thestructure and thickness of grey cast iron coating after alphinising.Arch Mater Sci Eng2007;28:437–40.[12]Zhang K,Bian XF,Li YM,Liu Y,Yang CC.New evidence for the formation andgrowth mechanism of the intermetallic phase formed at the Al/Fe interface.J Mater Res2013;28:3279–87.[13]Springer H,Kostka A,Payton EJ,Raabe D,Kaysser-Pyzalla A,Eggeler G.On theformation and growth of intermetallic phases during interdiffusion between low-carbon steel and aluminum alloys.Acta Mater2011;59:1586–600. [14]Choi SW,Kim YC,Kim CW,Cho JI,Kang CS,Kim YM.Effect of Mn on theInteraction between Die Casting Steel and Al Alloy.In:ICAA13:13th International Conference on Aluminum Alloys.John Wiley&Sons,Inc.;2012.p.225–9.[15]Liu Y,Bian XF,Yang JF,Zhang K,Feng L,Yang CC.An investigation ofmetallurgical bonding in Al–7Si/gray iron bimetal composites.J Mater Res 2013;28:3190–8.[16]Cheng XL,Gao YM,Fu HG,Xing JD,Bai BZ.Microstructural characterizationand properties of Al/Cu/Steel diffusion bonded joints.Met Mater Int 2010;16:649–55.[17]Papis KJM,Hallstedt B,Löffler JF,Uggowitzer PJ.Interface formation inaluminium–aluminium compound casting.Acta Mater2008;56:3036–43. [18]Zhao LM,Zhang ZD.Effect of Zn alloy interlayer on interface microstructureand strength of diffusion-bonded Mg–Al joints.Scripta Mater2008;58:283–6.[19]Liu LM,Zhao LM,Xu RZ.Effect of interlayer composition on the microstructureand strength of diffusion bonded Mg/Al joint.Mater Design2009;30:4548–51.[20]Song GM,Vystavel T,van der Pers N,De Hosson JTM,Sloof WG.Relationbetween microstructure and adhesion of hot dip galvanized zinc coatings on dual phase steel.Acta Mater2012;60:2973–81.[21]Laukant L,Wallmann C,Müller M,Korte M,Stirn B,Haldenwanger HG,et al.Fluxless laser beam joining of aluminium with zinc coated steel.Sci Technol Weld Joi2005;10:219–26.[22]Chen YC,Nakata K.Effect of the surface state of steel on the microstructure andmechanical properties of dissimilar metal lap joints of aluminum and steel by friction stir welding.Metall Mater Trans B2008;39:1985–92.[23]Yang SL,Zhang J,Lian J,Lei YP.Welding of aluminum alloy to zinc coated steelby cold metal transfer.Mater Design2013;49:602–12.[24]Tan CW,Li LQ,Chen YB,Guo ser-tungsten inert gas hybrid welding ofdissimilar metals AZ31B Mg alloys to Zn coated steel.Mater Design 2013;49:766–73.[25]Ma JJ,Harooni M,Carlson B,Kovacevic R.Dissimilar joining of galvanized high-strength steel to aluminum alloy in a zero-gap lap joint configuration by two-pass laser welding.Mater Design2014;58:390–401.[26]Oh-ishi K,Edalati K,Kim HS,Hono K,Horita Z.High-pressure torsion forenhanced atomic diffusion and promoting solid-state reactions in the aluminum–copper system.Acta Mater2013;61:3482–9.[27]Ghuman ARP,Goldstein JI.During the hot dipping of iron in0to10pct Al–Znbaths at450–700°C.Metall Trans1971;2:2903–14.[28]O’dell S,Charles J,Vlot M,Randle V.Modelling of iron dissolution during hotdip galvanising of strip steel.Mater Sci Tech2004;20:251–6.[29]Marder AR.The metallurgy of zinc-coated steel.Prog Mater Sci2000;45:191–271.[30]Blumenau M,Norden M,Friedel F,Peters K.Reactive wetting during hot-dipgalvanizing of high manganese alloyed steel.Surf Coat Tech 2011;205:3319–27.[31]Perrot P,Tissier JC,Dauphin JY.Stable and metastable equilibria in the Fe–Zn–Al system at450°C.Zeitschrift für Metallkunde1992;83:786–90.[32]Raghavan V.Al–Fe–Zn(aluminum–iron–zinc).J Phase Equilib2003;24:546–50.[33]Kobayashi S,Yakou T.Control of intermetallic compound layers at interfacebetween steel and aluminum by diffusion-treatment.Mater Sci Eng A 2002;338:44–53.[34]Lee JM,Kang SB,Sato T,Tezuka H,Kamio A.Evolution of iron aluminide in Al/Fe in situ composites fabricated by plasma synthesis method.Mater Sci Eng A 2003;362:257–63.[35]Bai K,Wu P.Assessment of the Zn–Fe–Al system for kinetic study ofgalvanizing.J Alloy Compd2002;347:156–64.[36]Raghavan V.Al–Fe–Si(Aluminum–Iron–Silicon).J Phase Equilib Diff2009;30:184–8.[37]Tanihata H,Sugawara T,Matsuda K,Matsuda K,Ikeno S.Effect of casting andhomogenizing treatment conditions on the formation of Al–Fe–Si intermetallic compounds in6063Al–Mg–Si alloys.J Mater Sci1999;34:1205–10.[38]Liu ZK,Chang YA.Thermodynamic assessment of the Al–Fe–Si system.MetallMater Trans A1999;30:1081–95.[39]Al-Fadhalah KJ,Alhajeri SN,Almazrouee AI,Langdon TG.Microstructure andmicrotexture in pure copper processed by high-pressure torsion.J Mater Sci 2013;48:4563–72.Y.Liu et al./Materials and Design64(2014)287–293293。