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Recent advances in the kinetics of normal/abnormal grain growth: a review

Najafkhani Fateme, Kheiri Sara, Pourbahari Bita, Mirzadeh Hamed

Archives of Civil and Mechanical Engineering

2021

Vol. 21, no. 1

483--502

Recent progress in the kinetics of grain coarsening and abnormal grain growth (AGG) is presented in this overview article. The factors affecting the kinetics of grain growth is reviewed with the emphasis on the recent findings on the solute drag and Zener pinning effects as well as the special case of duplex alloys, where the latter is discussed for the behavior of dual-phase steels during intercritical annealing. The common isothermal kinetics models for grain growth are listed, which is followed by the critical discussion on the simplifications and the commonly used methods for the determination of grain growth exponent (n) and activation energy (Q). The obtained values of n and Q for several classes of important engineering alloys such as microalloyed steels, stainless steels, magnesium alloys, aluminum alloys, titanium alloys, and high-entropy alloys are summarized with the discussion on the obtained values of kinetics parameters and their deviation from the theoretical expectations. Finally, the factors leading to AGG (such as the coarsening and dissolution of pinning particles and the crystallographic texture), the proposed mechanisms (such as the solid-state wetting and the grain boundary faceting/defaceting phenomena), and the kinetics of AGG (based on the empirical power law and the similarity of AGG to primary recrystallization in the form of secondary recrystallization) are reviewed. This overview can shed light on the understanding of grain growth and its effects.

Densification and grain growth of TiO2-doped ZnO

Yildiz K., Karaku N., Toplan N., Toplan H. O.

Materials Science Poland

2007

Vol. 25, No. 4

1135--1142

The kinetics of grain growth in 1-4 wt. % TiO2-doped ZnO was studied using the simplified phenomenological grain growth kinetics equation together with examination of microstructure and densification of the sintered samples. The grain growth exponent values n were found to be 3 for 1 and 2 wt. % TiO2- doped ZnO, 5 for 3 and 4 wt. % TiO2-doped ZnO. The apparent activation energy of 435 kJ/mol was found for 1 and 2 wt. % of TiO2 in ZnO. It was found to be 608 kJ/mol and 615 kJ/mol for 3 and 4 wt. % TiO2, respectively. The apparent activation energy increased with TiO2 content due to formation of spinel Zn2TiO4 phase at the grain boundaries which inhibited the grain growth of ZnO. Also densification decreased with increasing TiO2 content.