Cr,Si Trace Elements on Steel/Aluminium Induction Hydrostatic Welding Joint Organization and Properties of the Impact
In order to promote the research on the automobile lightweighting,a induction-pressure welding method was used to join three groups of Fe/Al specimens for Q235 & 5052H32(No.l),40Cr & 5052H32(No.2)and Q235 & 6061-T6(No.3).The results show that the intermetallic compounds(IMC)at the interface consists of the tongue-like Fe2Al5 phase on the near-steel side and the needle-like FeAl3 phase on the near-aluminium side.The Gibbs free energy of the Fe2Al5 is less than that of the FeAl3,leading to the preferentially growth for Fe2Al5 at the interface.The average thicknesses of Fe2Al5 for specimens 1 to 3 were 20 μm,14 μm and 11μm,respectively.Compared with No.1 and No.2,it was found that the Cr element in 40Cr steel gathered at the interface and partially replaced the Fe element in IMC,reducing the diffusion coefficient of Al in Fe and inhibiting the formation of Fe2Al5,so that the thickness of Fe2Al5 for No.2 is smaller than that of No.l by 6 μm.Compared with No.l and No.3,it was found that the Si element in 6061-T6 aluminium alloy participated in the interfacial reaction and inhibited the growth of Fe2Al5 in the form of solid solution,so that the thickness of Fe2Al5 for No.3 is smaller than that of No.1 by 9 μm.The fracture mode of these three specimens were all mixed and the shear strengths of Nos.1,2 and 3 were 31 MPa,68 MPa and 73 MPa respectively.
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