Dynamic recrystallization and microstructure evolution of a powder metallurgy nickel-based superalloy under hot working
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ngwang Fu Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (Received 25 November 2015; accepted 11 May 2016)
The deformation behaviors (flow behavior, power dissipation, dynamic recrystallization, and microstructure evolution) of a typical powder metallurgy nickel-based superalloy were investigated in compression tests at temperatures range of 1020–1140 °C and strain rates range of 0.001–1.0 s1 with the true strains of 0.3, 0.5, and 0.7, respectively. The efficiency of power dissipation can be shown by the power dissipation maps at different true strains. The results showed that true strain had a great effect on the power dissipation. Besides, the deformed microstructures were investigated. The processes of microstructure evolution at different deformation temperatures and strain rates are different. The continuous dynamic recrystallization takes place at the deformation condition of 1080 °C/0.1 s1. The fine and uniform dynamic recrystallized grains gradually replace the pre-existing grains with the increase of true strain. The discontinuous dynamic recrystallization takes place at the deformation condition of 1110 °C/0.001 s1. The fine dynamic recrystallized grains grow up and a part of new fine grains appear in the dynamic recrystallized grains because of the periodic dynamic recrystallization.
I. INTRODUCTION
Hot plastic deformation as an important processing method has been widely used for making critical components. This process can not only provide the desired size and shape, but also produce excellent microstructure. The size and shape of component are changed in hot deformation process, which is accompanied by dynamic softening and microstructure evolution.1–3 Hot plastic deformation as a complex process includes work hardening, dynamic softening and microstructure evolution. All of them are affected by deformation temperature, strain rate, and true strain. And dynamic softening includes dynamic recovery and dynamic recrystallization, which determines the deformed microstructure and performance. Therefore, this is far and away the most important area of hot deformation. Superalloys have been widely used in manufacturing turbine engine blades or other bearing components working at high temperature because of their good microstructure stability, excellent mechanical properties, good ultimate strength, and creep performance at high temperature.4–7 With the continuous development of aerospace technology, alloying extent has become increasingly high. Traditional superalloys can no longer Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.204
satisfy the needs of the development of present aerospace technology. A new type of superalloy was produced by adopting the method of powder metallurgy processing with fine grain, uniform organization, no macro segregation, and high degree of alloying. FGH4096 superalloy as a kind of powder metallurgy superalloy has been widely appli
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