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Review of Literature Related to Microstructure Development During Laser Surface Engineering of Nickel Aluminum Bronze.
DEFENCE RESEARCH ESTABLISHMENT ATLANTIC DARTMOUTH (NOVA SCOTIA)
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In this report, literature related to the low heat input welding of nickel aluminum bronze is examined. This includes data on phases present, composition effects, phase diagrams, transformation kinetics, and the nature of martensites. Relevant data on microstructure development in castings, wrought materials, conventional welds and low heat input welds is considered. So is related work on the examination of melt spun ribbons and Gleeble studies. Available data show that a martensite with a 9-R structure is common in low heat input nickel aluminum bronze welds over a range of compositions. Other structures are expected at other compositions. Data also show that for at least one alloy composition, formation of Widmanstatten alpha can be suppressed with a high enough cooling rate. As well, data show that tempering of martensites in weld heat affected zones probably does not occur at temperatures of less than roughly 400 deg C. The review shows that experiments to obtain data on ordering, metastable reactions, precipitation, and tempering are needed. Also needed are experiments to understand the effect of composition and heat input on microstructure.
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