Transmission electron microscopy of martensitic phases formed in laser welded nickel aluminum bronze alloys

Transmission electron microscopy was used to study the effect of composition and processing conditions on the morphology and crystallography of the martensite and other phases formed in laser welded nickel aluminium bronze. Generally, the attendant rapid cooling results in the formation of complex multi-component microstructures composed of martensites, solid solution ($\alpha$) and intermetallic phases. The TEM observations reveal that disordered $\beta '$ or 9R martensite is formed under these conditions, with considerable morphological variation that is sensitively related to composition and detailed thermal history. The influence of Ti, Zr and Cr alloving additions on martensite formation is outlined, suggesting avenues for the design of optimized consumable alloys for laser welding of nickel aluminium bronzes in various applications