|About this Abstract
|MS&T23: Materials Science & Technology
|Interface-mediated Phenomena in Structural Materials
|Heterogeneous Nucleation of γ’ Precipitates at Annealing Twin Boundaries in Superalloys: A Phase Field Study
|Vignesh Karunakaran, Longsheng Feng, Hariharan Sriram, Semanti Mukhopadhyay, Michael J. Mills, Yunzhi Wang
|On-Site Speaker (Planned)
Annealing twin boundaries (ATBs) in Ni-base superalloys have strong impacts on their mechanical properties such as fatigue and creep. In the meantime, ATBs also draw impurity segregation, host localized phase transformation, and serve as heterogeneous nucleation sites of γ’ precipitates. Experimental observations show three types of precipitation behavior at ATBs, preferable, non-preferable, and neutral. Since precipitates at ATBs will alter the stress field and dislocation activities in the vicinity, it may alter the influence of ATBs on the fatigue and creep properties as well. Thus, it is critical to understand the precipitate-ATB interactions during precipitation. This work investigates the influence of chemical free energy, twin boundary energy and elastic strain energy as function of alloy composition, aging temperature and cooling rate on γ’ nucleation at ATBs by using CALPHAD modeling and phase-field simulations. The contributions of these factors to the different precipitation behaviors observed in the experiments will be highlighted.