Cao Chezheng, Yao Gongcheng, Jiang Lin, Sokoluk Maximilian, Wang Xin, Ciston Jim, Javadi Abdolreza, Guan Zeyi, De Rosa Igor, Xie Weiguo, Lavernia Enrique J, Schoenung Julie M, Li Xiaochun
Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA.
Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA.
Sci Adv. 2019 Aug 23;5(8):eaaw2398. doi: 10.1126/sciadv.aaw2398. eCollection 2019 Aug.
Cooling, nucleation, and phase growth are ubiquitous processes in nature. Effective control of nucleation and phase growth is of significance to yield refined microstructures with enhanced performance for materials. Recent studies reveal that ultrafine grained (UFG)/nanocrystalline metals exhibit extraordinary properties. However, conventional microstructure refinement methods, such as fast cooling and inoculation, have reached certain fundamental limits. It has been considered impossible to fabricate bulk UFG/nanocrystalline metals via slow cooling. Here, we report a new discovery that nanoparticles can refine metal grains to ultrafine/nanoscale by instilling a continuous nucleation and growth control mechanism during slow cooling. The bulk UFG/nanocrystalline metal with nanoparticles also reveals an unprecedented thermal stability. This method overcomes the grain refinement limits and may be extended to any other processes that involve cooling, nucleation, and phase growth for widespread applications.
冷却、成核和相生长是自然界中普遍存在的过程。有效控制成核和相生长对于获得具有增强性能的细化微观结构的材料具有重要意义。最近的研究表明，超细晶粒（UFG）/纳米晶金属具有非凡的性能。然而，传统的微观结构细化方法，如快速冷却和孕育，已经达到了一定的基本极限。人们一直认为通过缓慢冷却不可能制造出块状UFG/纳米晶金属。在此，我们报告一项新发现，即纳米颗粒可以通过在缓慢冷却过程中注入连续的成核和生长控制机制，将金属晶粒细化至超细/纳米尺度。含有纳米颗粒的块状UFG/纳米晶金属还展现出前所未有的热稳定性。该方法克服了晶粒细化的限制，并且可能扩展到任何其他涉及冷却、成核和相生长的过程，以实现广泛应用。
