Effect of composition of Zn-Al series solder on microstructure and properties of steel/aluminum pipes by magnetic pulse semi-solid soldering

Objective This study aims to investigate effects of Al and Si content on elemental diffusion process and interfacial microstructure during magnetic pulse semi-solid soldering of steel/aluminum pipes with Zn-Al and Zn-Al-xSi solder, as well as their variation patterns. Methods Microstructure and mechanical properties of soldered joints with Zn-Al and Zn-Al-xSi solder were examined through shear tests, microhardness measurements, electron probe microanalysis (EPMA) and energy dispersive spectroscopy (EDS). Special emphasis was placed on analyzing the influence of intermetallic compounds on performance of soldered joints. Results The Zn15Al solder demonstrated superior suitability for steel/aluminum soldering compared to Zn3Al and Zn22Al, yielding better mechanical properties of soldered joints. The addition of Si to Zn-Al solder promoted the formation of ternary Si-Al-Fe intermetallic compounds with favorable properties, which effectively suppressed the formation and growth of brittle Fe/Al intermetallic compounds and enhanced mechanical properties of soldered joints. Conclusion Among Zn-Al solder, Zn15Al joint achieves the highest shear strength of 38.49 MPa. For Zn-Al-xSi solder, increasing Si content leads to grain refinement in the soldering seam. The optimal performance with shear strength of 45.07 MPa occurs at 1.5 wt.% Si.