Femtosecond laser rejuvenation of nanocrystalline metals

Metastable grain boundaries: the roles of structural and chemical disorders in their energetics, non-equilibrium kinetic evolution, and mechanical behaviors

“…Balbus et al investigated how laser irradiation leads to the variation of mechanical properties, i.e. hardness, in nanocrystalline metals [22]. In figure 7, the dependences of hardness on normalized laser fluence are presented for both the Al-4.8 at.%O and SC-Cu-Zr nanocrystals.…”

“…The existence of essentially infinite number of metastable microscopic states at the same macroscopic misorientation angle presents new opportunities to engineer and harness the properties of nanocrystalline materials by tuning only the microscopic degrees of freedom without altering samples' macroscopic textures. As an example, femtosecond laser irradiation has been discovered to induce substantial variations (up to 87%) in hardness in nanocrystals, despite negligible alterations in grain sizes [22]. In addition, recent experiments in AM underscore the capacity of non-equilibrium GBs to attain high diffusivity without discernible changes in grain sizes and orientations [23].…”

Building on Gleiter: The Foundations and Future of Deformation Processing of Nanocrystalline Metals

“…[83,100,101] These all serve to increase the alloy's stability against grain growth at high homologous temperatures (> 0.5 T/T m ) or, in some cases, suppress detrimental phase transformations, [102] besides also imparting many other exceptional mechanical properties. [103][104][105][106][107] A recent perspective piece by Spearot et al [108] specifically speaks to the mechanical properties of stabilized fcc metals, and some unexplored future research needs and opportunities. Some intriguing ideas presented include understanding the role of chemistry on the transition between dislocation-based plasticity and grain boundary-mediated plasticity in thermally stable alloys, along with appropriate constitutive models that also account for this transition.…”

“…But the potential for retention of strength is questionable and, if possible, it would need to occur through the suppression of recovery, grain growth and precipitate coarsening reactions. More recently Balbus et al [104] have shown that femtosecond laser pulsing can be used to relax (''rejuvenate'') nanocrystalline grain boundaries in Al-O and Cu-Zr alloys, resulting in an 87 pct decrease in hardness with no grain growth. The rapid heating and cooling, along with the stress-state induced by the femtosecond laser below the ablation threshold largely circumvent the concerns presented by Wilde and Divinski.…”

Исследование Деформации Композитных Материалов На Основе Метастабильных Сплавов Системы Железо-Хром-Никель Методом Корреляции Цифровых Изображений

“…Пластичные области аустенита (γ-фаза) могут быть получены в результате нагрева до температур обратного (α → γ) мартенситного превращения. Использование в качестве способа нагрева лазерного излучения позволяет влиять на структуру аморфных и кристаллических спла-вов [7][8][9][10][11][12][13][14] и, в частности, сплава Fe-18Cr-10Ni [5,6], где в результате локального воздействия лазерным излучением образуются области пластичного аустенита определенных форм и размеров, распределенные по заданному закону в высокопрочной мартенситной матрице. Проведенные в работе [5] исследования механических свойств таких материалов методами измерения величины микротвердости по Виккерсу показали, что использование термической обработки с применением лазерного излучения существенно повышает прочность образующегося аустенита, при этом не снижая его пластичности.…”