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Non-conventional transformation pathways and ultrafine lamellar structures in γ-TiAl alloys
Acta Materialia ( IF 9.4 ) Pub Date : 2020-05-01 , DOI: 10.1016/j.actamat.2020.02.053
Tianlong Zhang , Dong Wang , Jiaming Zhu , Hu Xiao , C.T. Liu , Yunzhi Wang

Abstract The mechanical properties of two-phase γ-TiAl alloys depend strongly on the scale of their lamellar microstructures. In this study, we investigate the effect of alloy composition on lamellar thickness in Ti100-xAlx by simulating microstructural evolution during the α2′ → α2 + γ phase transformation using the phase field method. From both existing experimental data and our simulation results we find that the average thickness of γ lamellae first decreases and then increases with increasing Al content. Further analyses reveal that this unique composition-dependence of the lamellar thickness could be associated with non-conventional pseudospinodal decomposition and congruent structural transformation mechanisms that generate ultra-high densities of nuclei at the initial stage, which impacts the later growth processes. The interplay between the number density of nuclei and the number of coalescence events during growth results in the non-monotonic dependence of the lamellar thickness on the alloy composition. These findings may offer new insights on the design of ultrafine lamellar microstructures for γ-TiAl alloys.

中文翻译:

γ-TiAl合金中的非常规转变途径和超细层状结构

摘要 两相γ-TiAl 合金的力学性能很大程度上取决于其层状组织的尺度。在这项研究中,我们通过使用相场法模拟 α2' → α2 + γ 相变过程中的微观结构演变,研究了合金成分对 Ti100-xAlx 层状厚度的影响。从现有的实验数据和我们的模拟结果我们发现,随着铝含量的增加,γ 片层的平均厚度先减小然后增加。进一步的分析表明,层状厚度的这种独特的成分依赖性可能与非常规假旋节分解和一致的结构转变机制有关,这些机制在初始阶段产生超高密度的核,从而影响后期的生长过程。晶核数密度与生长过程中聚结事件数之间的相互作用导致层状厚度对合金成分的非单调依赖性。这些发现可能为γ-TiAl合金的超细层状微观结构设计提供新的见解。
更新日期:2020-05-01
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