Influence of Preheating Temperature on Cold Metal Transfer (CMT) Welding Brazing of Aluminium Alloy/Galvanized Steel

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1 applied sciences Article Influence Preheating Temperature on Cold Metal Transfer (CMT) Welding Brazing Aluminium Alloy/Galvanized Steel Youqiong Qin 1,2, *, Xi He 1 Wenxiang Jiang 1 1 School Materials Engineering, Shanghai University Engineering Science, Shanghai 2162, China; hex126@163.com (X.H.); jiangwenxiang1994@163.com (W.J.) 2 Shanghai Collaborative Innovation Center Laser Advanced Manufacturing Technology, Shanghai 2162, China * Correspondence: qinyouqiong@sues.edu.cn Received: 2 August 218; Accepted: 11 September 218; Published: 14 September 218 Abstract: Bead-on-plate cold metal transfer (CMT) brazing overlap CMT welding brazing 775 aluminium alloy galvanized steel at different temperatures studied. The results indicated that AlSi5 filler wire had good wettability to galvanized steel. The treatment can promote spreadability liquid AlSi5. For overlap CMT welding brazed joint, microstructure joint divided into four zones, namely, layer, weld metal zone, zinc-rich zone, heat affected zone (HAZ). The load force joints without 1 C temperature 858 N 973 N, respectively. Both joints fractured in fusion line with a ductile fracture. Furr increasing temperature to 2 C would decrease load force joint, which fractured in layer with a brittle fracture. Keywords: 775 aluminium alloy; galvanized steel; CMT welding-brazing; microstructure; mechanical property 1. Introduction The growing dem for lightweight design in automotive industry arises a strong interest in joining aluminium alloy to steel. It is difficult to obtain a sound joining aluminium to steel because large differences in melting points, coefficient rmal conductivity, rmal expansion, especially formation intermetallic compound (IMC) at Fe/Al interface. According to Al Fe phase diagram, formation IMC inevitable during welding, due to poor solubility between Fe Al [1 3]. However, an excessive formation IMC resulted in brittleness in joints. The published results showed that thickness IMC should be below 1 µm, which critical value in order to obtain good mechanical properties in Fe/Al dissimilar metal welding [4,5]. The total thickness IMC primarily dominated by rmal diffusion related to rmal cycle (i.e., peak temperature duration) welding process [6]. The arc welding brazing process combined advantages welding brazing. Therefore, it a preferable method to join aluminium alloy steel, as it could suppress growth IMC obtain good mechanical properties Al/Fe joint. In this process, part aluminium alloy melted, but steel in a solid state. The melted filler wire aluminium alloy wetted solid steel surface. Meanwhile, Fe atoms diffused into melted metal, n IMC formed at interface steel/brazing metal. Appl. Sci. 218, 8, 1659; doi:1.339/app

2 Appl. Sci. 218, 8, x FOR PEER REVIEW 2 1 Appl. Sci. 218, 8, Meanwhile, Fe atoms diffused into melted metal, n IMC formed at interface steel/brazing metal. Except for for thickness IMC, IMC, wettability wettability width width length length also critical also factors criticalinfluencing factors influencing mechanical mechanical properties properties joints industrial joints manufacturing industrial manufacturing [7]. However, [7]. However, wettability wettability liquid aluminium liquidon aluminium a steel surface on a steel fairly surface poor, due to fairly presence poor, due an to oxide layer presence on an surface oxide layer base on material surface [8]. Usually, base material oxide [8]. layer Usually, removed oxide by layer flux or a removed cathodic cleaning by flux or method a cathodic so as cleaning to promote method so as [7]. to promote Moreover, wettability [7]. Moreover, can be improved wettability by zinc can coatings be improved by zinc coatings treatment on steel sheet [9 11]. treatment Therefore, on galvanized steel sheet steel [9 11]. ten Therefore, used galvanized as a base material. steel ten The Zn used coating as a base is electro-galvanized material. The Zn coating or hot-dip is electro-galvanized galvanized. The or thickness hot-dip galvanized. coating is The about thickness 5 11 μm [7]. coating The spreadability is about 5 11 µm [7]. Al-based The spreadability droplets on steel Al-based with droplets on greatly steel with improved, which indicated greatly that improved, which indicated treatment that process might be beneficial treatmentfor process obtaining mighta be sound beneficial Al/Fe for welding brazed obtaining a sound joint. Al/Fe In welding brazed metal inert gas joint. (MIG) Inwelding metal brazing inert gas (MIG) Al/Fe welding brazing with treatment, Al/Fe withh. Ma [1] treatment, G. Qin H. [11] Ma found [1] that G. Qin [11] found treatment that process can treatment increase process spreadablility can increase weld spreadablility seam obtain weld a higher seamstrength obtain with a a higher suitable strength preheat with temperature. a suitable preheat temperature. Cold transfer metal (CMT) is isa modified process by MIG welding. In In CMT process, filler wire is isintentionally retracted instantaneously, which which assists assists droplet droplet detachment detachment during during short circuit. short circuit. The short The circuit short current circuitis current kept small, is kept as shown small, in as shown1. in Compared 1. with Compared conventional with welding conventional processes, welding processes, melted metal can melted be transferred metal can be into transferred welding intopool welding without pool aid without an electromagnetic aid an electromagnetic force. It is characterized force. It is characterized by a low heat byinput a low heat no-spatter input welding, no-spatter which welding, is a preferable which is aprocess preferable to join process Al to join Fe, as Alreported Fe, as by reported R. Cao [12] by R. Cao Y.L [12] Zhou [13]. Y.L Zhou [13]. U I t t 1. Variations voltage current with time during cold metal transfer (CMT) process. 1. Variations voltage current with time during cold metal transfer (CMT) process. From above, low heat input CMT welding brazing process or treatment can be From above, low heat input CMT welding brazing process or treatment can used to increase strength joint. Thus, aim this study to investigate feasibility be used to increase strength joint. Thus, aim this study to investigate mechanism joining aluminium steel. The 775-T651 aluminium alloy with a high strength feasibility mechanism joining aluminium steel. The 775-T651 aluminium alloy with a (more than 538 MPa) low density (2.81 g/cm 3 ) is used, which is suitable for structures high strength (more than 538 MPa) low density (2.81 g/cm 3 ) is used, which is suitable for components that are subjected to static dynamic loads. Bead-on-plate CMT brazing used to structures components that are subjected to static dynamic loads. Bead-on-plate CMT better underst characteristics brazing metal on steel. The microstructure brazing used to better underst characteristics brazing metal on steel. The mechanical properties overlap CMT welding brazing joints at different temperatures microstructure mechanical properties overlap CMT welding brazing joints at different also investigated. temperatures also investigated. 2. Experimental Methods 2. Experimental Methods 2.1. Materials Procedure 2.1. Materials Procedure The 775 aluminum alloy with a thickness 2.7 mm, galvanized steel with a thickness 2 mm, The 775 used aluminum as basealloy materials. with a The thickness thickness 2.7 mm, Zn coating galvanized on galvanized steel with a steel thickness about 2 mm, 11 µm. ER443 used as (AlSi5) base materials. with a diameter The thickness 1.2 mm Zn used coating as a filler on galvanized wire. Thesteel nominal about chemical 11 μm. compositions ER443 (AlSi5) base with materials a diameter 1.2 filler mm wire are used listed as in a filler Tablewire. 1. The nominal chemical compositions base materials filler wire are listed in Table 1.

3 Appl. Sci. 218, 8, Appl. Sci. 218, 8, x FOR PEER REVIEW 3 1 Table Table 1. Nominal 1. chemical composition base materials filler filler wire wire (wt.%). (wt.%). Materials Materials C C Si Si Fe Fe Cu Mn Mg Mg Zn Zn Al Al galvanized galvanized steel steel Bal. Bal Bal Bal. ER Bal. ER Bal. Bal. balance Bal. balance The The size size specimens mm mm 1 1 mm mm 2.7 mm 2.7 mm mm mm 1 mm 1 mm 2 mm 2 for mm775 aluminum for 775alloy aluminum galvanized alloy galvanized steel, respectively. steel, respectively. The equipment The equipment Fronius Fronius CMT 5 CMT i 5 welding i system. welding Before system. experiment, Before experiment, surface surface 775 aluminum 775 aluminum alloy alloy polished polished using SiC using paper up to SiCgrit paper 1, upto toremove grit 1, to oxide remove films, oxide films, ultrasonically ultrasonically cleaned by acetone. cleanedthe by acetone. galvanized steel The galvanized degreased steel by acetone degreased to remove by acetone grease. toin remove case bead-on-plate grease. In CMT case brazing, bead-on-plate AlSi5 filler wire CMT brazing, directly melted AlSi5 filler by a wire CMT arc, directly dropped melted on by a CMT surface arc, dropped steel, as on shown surface in 2a. steel, as shown in 2a. For overlap welding brazing aluminium alloy steel, For overlap welding brazing aluminium alloy steel, aluminum alloy placed on aluminum alloy placed on top steel. The overlap length 1 mm, as shown in top steel. The overlap length 1 mm, as shown in 2b. 2b Schematic CMT CMT joints. Bead-on-plate CMT brazing; overlap CMT CMT welding brazing. Prior to welding process, a heating resistance wire system equipped with temperature Prior to welding process, a heating resistance wire system equipped with temperature measurement control used to preheat base materials. The heating plate placed measurement control used to preheat base materials. The heating plate placed beneath steel. The melting temperature Zn is about 42 C, strength Al/Fe MIG beneath steel. The melting temperature Zn is about 42 C, strength Al/Fe MIG welding brazed joint decreased when temperature up to 2 C, as reported by H. welding brazed Ma [1]. The joint decreased temperature when chosen as 1 temperature C 2 C. In up welding to 2 C, process, as reported argon, by H. Ma with[1]. a flow The rate L/min, temperature a contact tip-to-work chosen as 1 distance C 11 2 mm C. In used welding throughout process, argon, experiments. with a flow The rate bead-on-plate L/min, brazing a contact overlaptip-to-work welding brazing distance processing 11 parameters mm areused throughout given in Table experiments. 2. ConsideringThe additional bead-on-plate heat loss brazing rmal overlap conduction welding brazing 775 aluminium processing parameters alloy during are given overlap in Table CMT2. welding brazing, Considering additional welding speed heat loss set at.4rmal m/min, conduction lower than 775.5aluminium m/min welding alloy speed during bead-on-plate overlap CMT brazing. welding brazing, welding speed set at.4 m/min, lower than.5 m/min welding speed in bead-on-plate brazing. Table 2. Processing parameters bead-on-plate brazing overlap welding brazing. Table 2. Processing parameters Wire Feeding bead-on-plate Weldingbrazing Speed overlap welding brazing. Preheating Temperature ( Speed (m/min) (m/min) C) Wire Feeding Welding Speed Bead-on-plate brazing Preheating Temperature ( C) Speed (m/min) 5 (m/min).5 Room temperature, 1, 2 Overlap Bead-on-plate welding brazing brazing Room Room temperature, temperature, 1, 1, 2 2 Overlap welding brazing 5.4 Room temperature, 1, Analysis Methods 2.2. Analysis AfterMethods joining, width length (L) angle (θ) measured on cross After sections joining, eachwidth seam. The width length (L) length ranged from angle one(θ) triple point measured to or on cross sections each seam. The width length ranged from one triple point to or triple point (bead-on plate brazing) or welding root (overlap CMT welding brazing). The angle determined to be angle between steel interface tangent applied along outer bound spherical cap at a magnification 1:1. The bead-on-plate brazing overlap

4 x FOR PEER REVIEW Appl. Sci. 218, 8, EM) coupled with an energy dispersive spectrometer (EDS) used t tensile tests done by an AG-25TA machine. The specimens co d 1 mm/min, size specimen is illustrated in 3. At l re used to obtain average tensile force. The micro-hardness test ad 1 g for s. triple point (bead-on plate brazing) or welding root (overlap CMT welding brazing). The angle determined to be angle between steel interface tangent applied along outer bound spherical cap at a magnification 1:1. The bead-on-plate brazing overlap welding brazing samples polished for microstructure evaluation. A scanning electron microscopy (SEM) coupled with an energy dispersive spectrometer (EDS) used to characterize joint. The tensile tests done by an AG-25TA machine. The specimens compressed at a constant speed 1 mm/min, size specimen is illustrated in 3. At least three test specimens used to obtain average tensile force. The micro-hardness tested by a Micro Vickers, at a load 1 g for s. Discussion 3. Geometry specimen for tensile test. 3. Geometry specimen for tensile test. 3. Results Discussion 3.1. Wettability Characteristics Bead-on-Plate Brazing Metallographic cross sections different bead-on-plate brazing specimens are shown in 4. The width length (L) angle (θ) at different temperatures are given in 5. It found that all angles below 9. Compared with joint without, width length longer angle lower with Characteristics Bead-on-Plate Brazing treatment. The width length increased angle decreased with increasing temperature. The minimum angle (3 ) maximum raphic cross widthsections length (different mm) obtained bead-on-plate at a 2 C temperature. brazing Thisspecimens indicated that are sh liquid AlSi5 filler wire had a good wettability on galvanized steel. The treatment f could increase length spreading (L) AlSi5 filler wire. angle (θ) at different tem e 5. It found that all angles below 9. Compared ating, width length longer angle w treatment. The width length increased an asing temperature. The minimum angle (3 ) t ing length ( mm) obtained at a 2 C temperature. T d AlSi5 filler wire had a good wettability on galvanized steel. T ld increase spreading AlSi5 filler wire.

5 without, width length longer angle lower with treatment. The width length increased angle decreased with increasing temperature. The minimum angle (3 ) maximum width length ( mm) obtained at a 2 C temperature. This indicated Appl. that Sci. 218, liquid 8, 1659 AlSi5 filler wire had a good wettability on galvanized steel. The 5 1 treatment could increase spreading AlSi5 filler wire. Appl. Sci. 218, 8, x FOR PEER REVIEW 5 1 (c) 4. Metallographic cross sections for bead-on-plate brazing at different temperatures. 4. Metallographic cross sections for bead-on-plate brazing at different temperatures. Without ; 1 Without ; 1 C; (c) 2 C; (c) 2 C. C. 2 L q 6 Width length(mm) Wetting angle( ) Preheating temperature( ) 5. Width length angle at different temperatures Influence Preheating Temperature on Overlap Welding Brazing Aluminium Alloy 3.2. Galvanized Influence Steel Preheating Temperature on Overlap Welding Brazing Aluminium Alloy Galvanized Steel The cross sections overlap welding brazing specimens are shown in 6. The width The cross length sections (L) overlap angle welding brazing (θ) at different specimens temperatures are shown in are given 6. in The width 7. As can be observed length in s (L) 6 7, angle (θ) at angles different higher temperatures widths are given in length 7. As can lower be observed than those in for s bead-on-plate 6 7, brazing angles at same higher temperatures widths (see length 5). This lower because than those width for bead-on-plate length or brazing at angle same influenced temperatures not only by (see heat input 5). This arc because treatment, width but also by length heat or transfer steel angle influenced not only by heat input arc treatment, but also by heat transfer steel aluminium. Compared with bead-on-plate brazing, extra fast heat transfer by 775 aluminium alloy led to heat loss. Meanwhile, variation tendency width length angle with different temperature same as beadon-plate brazing. The variation trend same as MIG welding brazing reported in

6 The cross sections overlap welding brazing specimens are shown in 6. The width length (L) angle (θ) at different temperatures are given in 7. As can be observed in s 6 7, angles higher widths length lower than those for bead-on-plate brazing at same Appl. temperatures Sci. 218, 8, 1659 (see 5). This because width length or 6angle 1 influenced not only by heat input arc treatment, but also by heat transfer steel aluminium. Compared with bead-on-plate brazing, extra fast heat aluminium. Compared with bead-on-plate brazing, extra fast heat transfer by 775 transfer by 775 aluminium alloy led to heat loss. Meanwhile, variation tendency width aluminium alloy led to heat loss. Meanwhile, variation tendency width length angle with different temperature same as beadon-plate brazing. The variation trend same as MIG welding brazing reported in length angle with different temperature same as bead-on-plate brazing. The variation trend same as MIG welding brazing reported in literature [1]. literature [1]. Appl. Appl. Sci. Sci. 218, 218, 8, 8, x FOR FOR PEER PEER REVIEW REVIEW (c) (c) Metallographic Metallographic cross cross sections sections for for overlap overlap welding brazing welding brazing at at different different temperatures. temperatures. Without Without ; ; 1 1 C; C; (c) (c) 2 2 C. C. Width length(mm) L L q q Wetting angle( ) Preheating Preheating temperature( ) temperature( ) Width Width length length angle angle at at different different temperatures. temperatures. 8 8 shows shows shows typical typical typical microstructures microstructures microstructures CMT welding brazing CMT CMT welding brazing welding brazing joint (without joint joint ). (without (without Table ). ). 3 gives Table Table average 3 gives gives chemical average average compositions chemical chemical each compositions compositions zone. According each each to zone. zone. microstructure According According features, to to microstructure microstructure features, features, microstructures microstructures joint joint divided divided into into four four different different zones, zones, namely: namely: layer, layer, weld weld metal metal zone, zone, Zn-rich Zn-rich zone, zone, heat heat affected affected zone zone (HAZ). (HAZ). An An irregular irregular layer layer (A) (A) occurred occurred at at interface interface steel steel brazing brazing filler. filler. From From EDS EDS result, result, layer layer mainly mainly contained contained Al Al Fe. Fe. No No Zn Zn found found in in layer. layer. According According to to phase phase diagram diagram Fe Al Fe Al [14], [14], it it probably probably Fe Al Fe Al IMC. IMC. The The thickness thickness IMC IMC

7 The hardness fusion line (about 116 HV.1) HAZ (about 146 HV.1) is higher than that in weld metal zone (79 HV.1), as shown in 8d. The minimum hardness is obtained in weld metal zone, n hardness increased rapidly to a higher level in HAZ adjacent to fusion line. The peak temperature HAZ nearest to fusion line exceeds fully dissolved Appl. temperature Sci. 218, 8, 1659 η η phases. The η η phases dissolve during welding dissolve out 7 1 in cooling stage, thus hardness HAZ nearest to fusion line is about 146 HV.1, which is lower than that base material (about 18 HV.1). The fusion line is between weld metal zone microstructures HAZ. The microstructure joint divided fusion into line four is very different heterogeneous, zones, namely: thus it is one weaker layer, weld regions metal zone, joint. Zn-rich zone, heat affected zone (HAZ). (c) (d) 8. Microstructures bead-on-plate brazing (without ): layer; weld metal zone; (c) Zn-rich zone; (d) heat affected zone (HAZ) zone. Table 3. Energy dispersive spectrometer (EDS) energy spectrum analysis. Table 3. Energy dispersive spectrometer (EDS) energy spectrum analysis. Location Location Fe Fe Al Al Zn Zn Si Si Possible Possible Phase Phase A A Fe Al Fe Al intermetallic B α-al B α-al C Al Si eutectic phase D C Al Si Al Zn eutectic solid solution phase D Al Zn solid solution An irregular layer (A) occurred at interface steel brazing filler. From 9 gives microstructures layer obtained at different EDS result, layer mainly contained Al Fe. No Zn found in layer. temperatures. Compared with joint without, thickness layer According to phase diagram Fe Al [14], it probably Fe Al IMC. The thickness slightly increased with temperature at 1 C. By furr increasing IMC layer about 1.5 µm, as shown in 8a. During welding brazing process, arc temperature at 2 C, thickness layer can be increased to 3.5 μm, which is lower heat melted AlSi5 filler wire increased temperature steel. The Zn coating within region heavy heating easy to evaporate, because low evaporating temperature Zn. At same time, a clean surface steel obtained, which beneficial to. This main reason that galvanized steel with a thin zinc layer on surface well wetted without flux. 8b shows microstructure weld metal zone (B). B mainly consisted Al C composed 76.9 at.% Al 2.3 at.% Si. Because original filler wire Al 5 wt.% Si. The microstructure weld metal like phases original filler wire. So B α-al solid solution. C Al Si eutectic phase. The Zn-rich zone (D) contained 7.38 at.% Al at.% Zn. According to Al Zn phase diagram [14], it most likely an Al Zn solid solution. The Zn-rich zone existed at weld toe.

8 Appl. Sci. 218, 8, Based on characteristics arc, temperature in center arc higher than vaporization temperature Zn. Little Zn residual after welding brazing. However, in edge arc, temperature probably lower than vaporization temperature Zn, consequently, Zn dissolved into melted Al-based filler metal, forming Zn-rich phase ( 8c). During welding brazing process, microstructure base material near weld metal zone affected changed by heat conducted to base material, as shown in 8d. The phenomenon grain boundary melting occurred in HAZ zone nearest to weld metal. The hardness fusion line (about 116 HV.1 ) HAZ (about 146 HV.1 ) is higher than that in weld metal zone (79 HV.1 ), as shown in 8d. The minimum hardness is obtained in weld metal zone, n hardness increased rapidly to a higher level in HAZ adjacent to fusion line. The peak temperature HAZ nearest to fusion line exceeds fully dissolved temperature η η phases. The η η phases dissolve during welding dissolve out in cooling stage, thus hardness HAZ nearest to fusion line is about 146 HV.1, which is lower than that base material (about 18 HV.1 ). The fusion line is between weld metal zone HAZ. The microstructure fusion line is very heterogeneous, thus it is one weaker regions joint. 9 gives microstructures layer obtained at different temperatures. Compared with joint without, thickness layer slightly increased with temperature at 1 C. By furr increasing Appl. Sci. 218, 8, x FOR PEER temperature at 2 REVIEW 8 1 C, thickness layer can be increased to 3.5 µm, which is lower than thickness total layer (about 6 mm) at 2 C temperature in than thickness total layer (about 6 mm) at 2 C temperature in literature [1]. literature [1]. 9. Microstructures layer layerat atdifferent different temperatures temperatures 1 1 C; C; 2 C. The mechanical properties, fracture location, fracture surface at different temperatures are shown in s The tensile load welding brazed joint without 858 N, tensile load obtained with with a 1 a 1 C C temperature N. Both N. Both joints joints fractured fractured at at fusion fusion line. line. This This because because thickness thickness IMC IMC thin, thin, tensile tensile force force fusion fusion line online on Al sideal side sufficient sufficient to cause to cause fracture fracture before before tensile shearing tensile shearing force orce layer on layer steel on side steel would side would cause cause fracture. fracture. Moreover, Moreover, because because base materials base materials to 1 to C, 1 C, cooling cooling speed speed welding stress welding stress joint decreased, joint which decreased, led towhich higherled strength to higher strength fusion line. But when fusion line. basebut materials when base preheated materials to 2 C, preheated tensile to load 2 decreased C, tensile to 5636 load N. decreased The cracksto occurred 5636 N. at The cracks occurred layer. at Although width layer. Although width length a 2 Clength temperature 2 C larger temperature than se recorded larger than without se recorded without at 1 C temperature, 1 C thicker temperature, IMC with thicker lower shear IMC with strength lower shear strength led to a low tensile load. Fracture surfaces joints displayed in 11 indicated that a brittle fracture occurred at IMC layer, while that in fusion line ductile. 1 fractured in Fuson line fractured in Fuson line

9 thin, tensile force fusion line on Al side sufficient to cause fracture before tensile shearing force layer on steel side would cause fracture. Moreover, because base materials to 1 C, cooling speed welding stress joint decreased, which led to higher strength fusion line. But when base materials preheated to 2 C, tensile load decreased to 5636 N. The cracks occurred at layer. Appl. Sci. 218, 8, Although width length at 2 C temperature larger than se recorded without at 1 C temperature, thicker IMC with ledlower to a low shear tensile strength load. led Fracture to a low surfaces tensile load. joints Fracture displayed surfaces in joints 11 indicated displayed that in a brittle11 fracture indicated occurred that a at brittle IMC fracture layer, occurred while that in IMC fusion layer, line while that ductile. in fusion line ductile. Tensile Load(N) fractured in Fuson line fractured in Fuson line fractured in layer Preheating temperature( ) Appl. Sci. 218, 8, x FOR PEER Tensile REVIEW force force fracture position at different at temperatures Conclusions 11. Fracture surface joints. In fusion line; in layer. In this thispaper, aluminium aluminium galvanized steel steel joined joined by CMT by CMT welding brazing. welding brazing. The The influence influence temperature temperature on on characteristics characteristics bead-on-plate bead-on-platebrazing, brazing, as well as as microstructure mechanical properties overlap welding brazing are investigated. The results are as as follows: In case bead-on-plate brazing, melted AlSi5 filler wire had a good wettability to galvanized steel. The treatment decreased angle significantly increased width length. Compared with bead-on-plate brazing, angle overlap welding brazing large because high heat conductivity 775 aluminium alloy. There four characteristic zones overlap in in welding brazing joint, namely: layer, weld weld metal metalzone, Zn-rich Zn-richzone, zone, HAZ. HAZ. The The layer layer Fe Al Fe Al brittle brittle IMC. IMC. The The thickness thickness layer layer increased increased with with increased increased temperature. temperature. The tensile load joint without lower than that at a 1 C C temperature. Both m fractured in fusion line with a ductile fracture. Furr increasing temperature temperature to to 2 2 C would C would decrease decrease tensile tensile load load joint. The joint. fracture The occurred fracture at occurred at layer because layer because thicker IMC thicker layer. IMC layer. Author Contributions: Y.Q.Q. X.H. conceived designed experiments; W.X.Z. performed experiments; Author Contributions: Y.Q.Q. X.H. Y.Q.Q. arranged X.H. analyzed conceived acquired designed data; Y.Q.Q. experiments; wrote manuscript; W.X.Z. performed The authors have experiments; all read Y.Q.Q. approved X.H. submitted arranged version analyzed manuscript. acquired data; Y.Q.Q. wrote manuscript; The authors have all read approved submitted version manuscript. Funding: This research financially supported by Shanghai Science Technology Committee Innovation Grant (17JC146, 17JC1461). Conflicts Interest: The authors declare no conflict interest.

10 Appl. Sci. 218, 8, Funding: This research financially supported by Shanghai Science Technology Committee Innovation Grant (17JC146, 17JC1461). Conflicts Interest: The authors declare no conflict interest. References 1. Li, X.; Scherf, A.; Heilmaier, M.; Stein, F. The Al-Rich Part Fe-Al Phase Diagram. J. Phase Equilib. Diffus. 216, 37, [CrossRef] 2. Pouranvari, M.; Abbasi, M. Dissimilar gas tungsten arc weld-brazing Al/steel using Al-Si filler metal: Microstructure strengning mechanisms. J. Alloys Compd. 218, 749, [CrossRef] 3. Pouranvari, M. Critical assessment: Dissimilar resistance spot welding aluminium/steel: Challenges opportunities. Mater. Sci. Technol. 217, 33, [CrossRef] 4. Agudo, L.; Weber, S.; Wagner, J.; Eyidi, D.; Schmaranzer, C.H.; Arenholz, E.; Jank, N.; Bruckner, J.; Pyzalla, A.R. Intermetallic Fe x Al y -phases in a steel/al-alloy fusion weld. J. Mater. Sci. 27, 42, [CrossRef] 5. Yang, S.; Zhang, J.; Lian, J.; Lei, Y. Welding aluminum alloy to zinc-coated steel by cold metal transfer. Mater. Des. 213, 49, [CrossRef] 6. Springer, H.; Kostka, A.; Payton, E.J.; Raabe, D.; Kaysser-Pyzalla, A.; Eggeler, G. On formation growth intermetallic phases during interdiffusion between low-carbon steel aluminum alloys. Acta Mater. 211, 59, [CrossRef] 7. Gatzen, M.; Radel, T.; Thomy, C.; Vollertsen, F. Wetting solidification characteristics aluminium on zinc coated steel in laser welding brazing. J. Mater. Process. Technol. 216, 238, [CrossRef] 8. Gatzen, M.; Radel, T.; Thomy, C.; Vollertsen, F. The role zinc layer during aluminium on zinc-coated steel in laser brazing welding. Phys. Procedia 214, 56, [CrossRef] 9. Liu, J.; Jiang, S.; Shi, Y.; Cong, N.; Chen, J.; Huang, G. Effects zinc on laser welding an aluminum alloy galvanized steel. J. Mater. Process. Technol. 2, 224, Ma, H.; Qin, G.; Wang, L.; Meng, X.; Chen, L. Effects preheat treatment on microstructure evolution properties brazed-fusion welded joint aluminum alloy to steel. Mater. Des. 216, 9, [CrossRef] 11. Qin, G.; Lei, Z.; Su, Y.; Fu, B.; Meng, X.; Lin, S. Large spot laser assisted GMA brazing-fusion welding aluminum alloy to galvanized steel. J. Mater. Process. Technol. 214, 214, [CrossRef] 12. Cao, R.; Yu, G.; Chen, J.H.; Wang, P.C. Cold metal transfer joining aluminum alloys-to-galvanized mild steel. J. Mater. Process. Technol. 213, 213, [CrossRef] 13. Zhou, Y.L.; Lin, Q.L. Wetting galvanized steel by Al 443 alloys in first cycle CMT process. J. Alloys Compd. 214, 589, [CrossRef] 14. Baker, H.; Okamoto, H. ASM Hbook Volume 3: Alloy Phase Diagrams; ASM International: Materials Park, OH, USA, by authors. Licensee MDPI, Basel, Switzerl. This article is an open access article distributed under terms conditions Creative Commons Attribution (CC BY) license (