Investigation of Strain Induced Precipitation of γ' Phase of AD730 Ni base Superalloy Using Stress Relaxation Technique

Document Type : Original Article

Authors

Zahra Mirzaie ¹

Gholamreza Ebrahimi ²

Hamid Reza Ezatpour ³

¹ Department of Materials and Polymers Engineering, Faculty of Engineering, Hakim Sabzevari University, Sabzevar, Iran.

² Department of Materials Science and Engineering, Engineering Faculty, Ferdowsi University of Mashhad, Azadi Square, Mashhad, Iran

³ Department of Materials Engineering, Valieasr University of Rafsanjan, Rafsanjan, Iran

10.22067/jmme.2025.92945.1203

Abstract

In the present work, the effect of deformation on the precipitation of the γʹ -phase in the as cast nickel-based superalloy of AD730 is investigated in the temperature range of 950-1050 °C and strain rate of 0.1 s-1, using the stress relaxation technique. It is indicated that γ´ precipitation leads to a slope change in the stress relaxation curves as a result of retardation of the stress relaxation in AD730. The precipitation-time-temperature (PTT) diagram shows that with increasing the test temperature from 950 ℃ to 1000 °C, the start time of precipitation decreases and then increases until the temperature of 1050 °C, which confirms the effect of temperature on the precipitation kinetics of γʹ phase. Microstructural studies designate that by increasing test temperature and duration time at constant strain, the size of γʹ precipitates increases with two mechanisms of agglomeration and competitive growth. The slope change at the end of the relaxation curves indicates that these precipitations play no role in strengthening as a result of the increase of softening work.

Keywords

AD730 Ni base superalloy

Dynamic precipitation

Stress relaxation test

γʹ precipitation

Subjects

• Metal Forming

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