Materials Science and Engineering, Arizona State University, Tempe, AZ, 85287, USA.
Advanced Photon Source, Argonne National Laboratory, Building 401, 9700 S. Cass Avenue, Argonne, IL, 60439, USA.
Adv Mater. 2017 Nov;29(41). doi: 10.1002/adma.201703482. Epub 2017 Sep 14.
Dispersions of nanoscale precipitates in metallic alloys have been known to play a key role in strengthening, by increasing their strain hardenability and providing resistance to deformation. Although these phenomena have been extensively investigated in the last century, the traditional approaches employed in the past have not rendered an authoritative microstructural understanding in such materials. The effect of the precipitates' inherent complex morphology and their 3D spatial distribution on evolution and deformation behavior have often been precluded. This study reports, for the first time, implementation of synchrotron-based hard X-ray nanotomography in Al-Cu alloys to measure kinetics of different nanoscale phases in 3D, and reveals insights behind some of the observed novel phase transformation reactions. The experimental results of the present study reconcile with coarsening models from the Lifshitz-Slyozov-Wagner theory to an unprecedented extent, thereby establishing a new paradigm for thermodynamic analysis of precipitate assemblies. Finally, this study sheds light on the possibilities for establishing new theories for dislocation-particle interactions, based on the limitations of using the Orowan equation in estimating precipitation strengthening.
纳米级沉淀物在金属合金中的弥散分布被认为是强化的关键，因为它可以提高应变硬化能力并提供对变形的抵抗力。尽管在上个世纪已经对这些现象进行了广泛的研究，但过去采用的传统方法并没有在这些材料中提供权威的微观结构理解。沉淀物固有的复杂形态及其 3D 空间分布对演变和变形行为的影响经常被排除在外。本研究首次报道了在 Al-Cu 合金中使用基于同步加速器的硬 X 射线纳米断层摄影术来测量不同纳米级相的 3D 动力学，并揭示了一些观察到的新型相转变反应背后的见解。本研究的实验结果与 Lifshitz-Slyozov-Wagner 理论的粗化模型非常吻合，这在前所未有的程度上建立了沉淀组装的热力学分析的新范例。最后，本研究揭示了基于在估计沉淀强化时使用 Orowan 方程的局限性，为位错-颗粒相互作用建立新理论的可能性。
