铝合金不锈钢熔化钎焊_图文

1、Materials Science and Engineering A 528 (2011 61796185Contents lists available at ScienceDirect Materials Science and EngineeringAj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /m s eaMicrostructure characteristics and mechanical property of aluminum alloy/stainless steel la

2、p joints fabricated by MIG weldingbrazing processHongtao Zhang a ,Jiakun Liu aaSchool of Materials Science and Engineering,Harbin Institute of Technology at Weihai,Weihai 264209,Chinaa r t i c l e i n f o Article history:Received 15March 2011Received in revised form 12April 2011Accepted 14April 2011

3、Available online 21 April 2011Keywords:Aluminum SteelWeldingbrazing MicrostructureMechanical propertya b s t r a c t© 2011 Elsevier B.V. All rights reserved.1.IntroductionDissimilar metal joining offers the potential to utilize the advan-tages of different materials often providing a whole stru

4、cture with unique mechanical property.Aluminum can reduce the weight of structural parts for its light weight and stainless steel has a high strength and excellent corrosion resistance.Hybrid structures of aluminum alloy and stainless steel are suggested in spacecraft,automotive and steamship to imp

5、rove the fuel efciency,increase the y range and control air pollution by reducing the weight 13.Therefore,it has become a hot research eld in recent years to joining aluminum alloy and stainless steel together.It is also a great challenge to join these two materials together because of the large dif

6、ference between their melting points,the nearly zero solid solubility of iron in aluminum and the formation of brittle AlFe intermetallic compounds at elevated temperatures 46.Furthermore,differences in thermo-physical properties such as expansion coefcient,conductivity,and specic heat can lead to r

7、esidual stresses after fusion welding,which make the joints suffer from heavy cracking with brittle failure in service 7,8.In order to realize actual use of these hybrid structures,appropriate joining methods for aluminum/steel dissimilar metals joints are necessary.Some researches have used solid s

8、tate and fusion welding processes to join aluminum and steel.These welding processes included diffusion bonding 9,friction welding 10,electromag-Aluminum alloy 2B50and stainless steel 1Cr18Ni9Ti sheets with thickness of 1.0mm were used and the chemical compositions of two base metals are listed in T

9、ables 1and 2.6180H.Zhang,J.Liu /Materials Science and Engineering A 528 (2011 61796185Table 1Chemical composition of aluminum alloy 2B50(wt.%.Si Fe Cu Mn Zn Mg Ni Cr Ti Al 0.80.300.010.20.020.1BalTable 2Chemical composition of stainless steel 1Cr18Ni9Ti (wt.%.C Si Mn P S N

10、iCrFe 0.081.002.000.0350.0309.0012.0017.0019.00BalTable 3Chemical composition of 4043AlSi wire (wt.%.Si Fe Cu Mn Mg Zn Ti Al 4.56.050.050.100.20Bposited of Al 86Fe 14phase and AlNi phases.In the second group,the steel sheets were galvanized to generate zinc coating with thickness 15m

11、on steel surface.4043AlSi wire with the diameter of 1.2mm was chosen as the ller metal,whose chemical composition was listed in Table 3,and argon was selected as the protectinggas. coating.Welding parameters of Group 1(aluminized steel.Voltage (V15.055500.990Metallographic specimens of typical cross

12、-section of the welds were cut and then the specimens were polished by metallographic sandpapers of 240,400,600,800,1000SiC grades.A solution (1ml HF +1.5ml HCl +2.5ml HNO 3+95ml H 2Owas used to etch the metallographic specimens to reveal the general microstructure of the joints.The metallographic s

13、pecimens were observed by opti-cal microscope (OMand scanning electron microscope (SEM.A slice was also cut from the position near interfacial layer,and then thinned by plasma-pump to observe using a transmission electron microscopy (TEMwith energy dispersive spectroscopy (EDS.Three tensile specimen

14、s were cut from each weld to eval-uate the mechanical property of the joints,with a loading rate of 1mm/min.3.Results and discussion . H.Zhang,J.Liu /Materials Science and Engineering A 528 (2011 617961856181 KJ/cm. Table 5Welding parameters of Group 2(galvanized steel.Voltage (V15.056401.26Table 6E

15、DS results of compound in fusion zone.Elements wt.%at.%31.0918.78Fracture occurred at the interface between fusion zone and steel base metal as shown in Fig.7with tensile strength 60MPa.XRD analysis results of fracture surface in aluminum side conrmed that the interfacial layer contained Al 86Fe 14a

16、nd Al 0.7Fe 3Si 0.3phases as shown in Fig.8.Fig.12shows the BSE photos of the intermetallic compound layer of the joints obtained with different heat inputs.The inter-face between aluminum and intermediate layer is wavy,while the interface between intermediate layer and steel is relatively at.Thickn

17、ess of the intermetallic layer was not of uniform along the seamsteel interface,which varied from about 5m to 15m depending on the process parameters used in the experiments.Fig.13shows EDS analysis of the seamsteel interface layer in line scanning mode of joint No.6whose heat input is median.The av

18、erage thickness appears to be less than 10m.The EDS traces also suggest some amount of interdiffusion occurred during welding process.From the seam side to the steel side,the content of Al in the reaction layer decreased from 73.71at.%to 50.36at.%,while that of Fe in the reaction layer increased fro

19、m 12.65at.%to 29.92at.%.Table 765.9744.506182H.Zhang,J.Liu /Materials Science and Engineering A528 (2011 61796185 A small amount of Cr,Ni and Si was found in the reaction layer.However,Zn does not appear due to its large volatilizing loss during the welding process because of a low boiling point.Fig

20、.15shows the metallographic photo of fusion zone which was formed by the molten ller wire and aluminum alloybase3.2.4.Tensile property and failure locationcould H.Zhang,J.Liu /Materials Science and Engineering A 528 (2011 617961856183 reach 193.6MPa when the heat input is 0.846KJ/cm and the frac-tur

21、e occurred near the heat affected zone as shown in Fig.19. zone.width.joint. 6184 H. Zhang, J. Liu / Materials Science and Engineering A 528 (2011 61796185 Fig. 13. Line scanning analysis of the seamsteel interface layer of No. 6. Fig. 16. Enrichment of Si in the grain boundary (bright eld image. Fi

22、g. 14. TEM bright eld image and SAED pattern of interfacial intermetallic compound. Fig. 17. Zinc-rich zone in weld toe. Fig. 15. The metallographic photo of fusion zone. Fig. 18. Tensile strength of the weld under different heat input. H. Zhang, J. Liu / Materials Science and Engineering A 528 (201

23、1 61796185 6185 4. Conclusions Dissimilar metals joints between 2B50 aluminum alloy and stainless steel were made by MIG weldingbrazing with auxiliary coating promoting wetting property of ller metal. Appearance and transverse pattern and the microstructure characteristics of joints were investigate

24、d. Major conclusions of this study could be summarized as follows: Aluminized coating had a limited effect to promote the wettability of aluminum ller metal; there were a lot of intermetallic compounds in the aluminized steel surface, part of which was melted, and another part of the compounds got i

25、nto the fusion zone after fragmentation as a result of the weld heat input; there are obvious micro-cracks between the compound layer and the steel base metal; fracture occurred at the interfacial layer of the welded seam/steel, with a tensile strength of the lap joint reaching about 60 MPa. Sound d

26、issimilar metals joints between aluminum alloy and galvanized steel with excellent appearance formation was obtained; the joints had three visible regions: the fusion zone, the interfacial reaction layer and zinc-rich zone, according to the phase characteristics; a thin discontinuous intermediate la

27、yer was clearly observed at the weld interface, thickness of which varied from about 5 m to 15 m depending on the heat input in the experiments; intermetallic compound in the seam region close to the welding interface was Al4.5 FeSi; average tensile strength of lap joint reached 193.6 MPa when the h

28、eat input is 0.846 KJ/cm and fracture occurred at the heat affected zone near the weld. Acknowledgements The research was supported by Project 50905045 supported by the National Natural Science Foundation of China and State Key Lab of Advanced Welding Production Technology, Harbin Institute of Techn

29、ology. References Fig. 20. SEM photograph of the fracture in the aluminum side. 1 R. Qiu, S. Satonaka, C. Iwamoto, Mater. Des. 30 (2009 36863689. 2 Y. Shi, H. Zhang, W. Takehiro, J. Tang, Opt. Laser Eng. 48 (2010 732736. 3 M. Alexandre, S. Rajashekar, D. Alexis, S. Michel, M. Simone, G. Dominique, C

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