Effect of filler metal on microstructure and mechanical properties of manganese-aluminum bronze repair welds
(Materials and Metallurgical Engineering Department, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran)
Abstract: The repair welding of UNS C95700 manganese-aluminum bronze plates was done using different filler metals. The microstructure and mechanical properties of welds were studied. The main microstructural constituents were α, β and κ phases with different morphologies. The addition of manganese decreased the percentage of α phase in the microstructure of weldments from 80% (Mn-free weld) to 57% (12.5% Mn weld, mass fraction). The morphology of κ phase was lamellar in high nickel specimens and it was changed to a globular morphology for high manganese welds. Although the application of high manganese filler metal yielded the higher tensile and bending strengths of weldment compared with the weld using high nickel filler material, the optimum mechanical properties of repair welds were obtained using a non-alloy filler material (ERCuAl-A2) for the underlay and high manganese filler metal (ERCuMnNiAl) for filling passes. This weld presented an increase of 39% in tensile strength compared with the base metal, and no cracking was observed after bending test.
Key words: manganese-aluminum bronze; welding; filler metal; microstructure; mechanical properties