Effect of hot working on microstructure evolution of as-cast Nickel Aluminum Bronze alloy

• Effects of temperature and cooling rate on microstructure and hardness of NAB alloy.
• Occurred phase constituents of NAB were strongly influenced by heating temperature.
• High cooling rate led to increased amount of β′ and finer Widmanstatten structure.
• Obtained hardness values were well correlated with β′ and Widmanstatten structure.
• Different microstructure evolutions of NAB with and without deformation were found.

In this work, influences of temperature and hot working on microstructure evolution of a Nickel Aluminum Bronze alloy (NAB) were studied. First, as-cast NAB alloy was annealed and subsequently cooled in air for obtaining homogeneous structure. Microstructure and mechanical properties of NAB specimens before and after annealing were characterized by tensile test, hardness test, optical microscopy and scanning electron microscopy. Then, annealed NAB samples were heat treated at different temperatures between 750 °C and 1000 °C and rapidly cooled down to room temperature. The results showed that amounts and types of emerged microstructures and corresponding hardness strongly depended on the applied temperatures. Additionally, hot compression tests during the temperature range of 800 °C and 950 °C were performed for the annealed NAB alloy. After forming, specimens were cooled down with two different cooling rates of 40 °C/s and 100 °C/s. Developed microstructure and resulting hardness of the deformed NAB alloy were discussed regarding to the heat treating conditions.