The significance of intermetallic compounds formed during interdiffusion in aluminum and magnesium dissimilar welds

The new observations have been compared to data in the literature with the aim of providing an in-depth understanding of the detrimental effects of interfacial reaction in aluminum - magnesium dissimilar welding. Three Al-Mg binary IMC phases were identified, γ-Al12Mg17 and β-Al3Mg2, as well as ε-Al30Mg23. Indentation techniques showed that all the IMC phases had extremely low toughness (< 0.1 MPam1/2). FIB-assisted ring core milling revealed that both the β-Al3Mg2 and γ-Al12Mg17 phases contained large residual stresses. Greater tensile residual stress was measured in the β-Al3Mg2 phase, which, combined with a lower toughness and more rapid growth kinetics, explains why it is generally the 'weak link' in Al-Mg dissimilar joints.105