Continuous Measurements of Recrystallization and Grain Growth in Cobalt Super Alloys
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L605 (20Cr-15W-10Ni wt pct) and CCM (28Cr-6Mo wt pct) cobalt-based superalloys are candidates for a wide range of applications, from gas turbine components to biomedical implants. Attention is currently focused on the optimization of grain structure as an appropriate approach to increase yield stress without affecting significantly the ductility. In this study, the Laser Ultrasonics for Metallurgy (LUMet) technology is used to examine in situ the evolution of the mean grain size associated with recrystallization and grain growth during heat treatments from the cold-rolled state. The recrystallization process is completed at 1373 K (1100 °C) for L605 and 1273 K (1000 °C) for CCM. The subsequent grain growth rate in L605 is larger compared to CCM. Continuous measurements of the grain size evolution are found to be consistent with grain growth affected by solute drag. Through in situ measurements, the laser ultrasonic technology significantly accelerates the determination of metallurgical parameters allowing for fast optimization of process parameters required to meet specific applications.
KeywordsGrain Size Distribution Twin Boundary Elastic Anisotropy Isothermal Holding Ultrasonic Pulse
The authors would like to acknowledge the financial support received from the Natural Sciences and Engineering Research Council (NSERC) of Canada. Eiwa Co., Ltd in Japan is thanked for providing the material and test samples. Also, the authors would like to express gratitude to Dr. Julien Favre for fruitful discussions.
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