Enhanced thermal stability of nanograined metals below a critical grain size
Enhanced thermal stability of nanograined metals below a critical grain size
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DOI：
10.1126/science.aar6941
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发表时间：
2018-05-04
期刊：
影响因子：
56.9
通讯作者：
Lu, K.
中科院分区：
文献类型：
--
作者：
Zhou, X.;Li, X. Y.;Lu, K.
纳米颗粒材料的局限性在于它们在高温下容易变粗。当晶粒尺寸减小到纳米级时，晶粒在更低的温度下发生粗化，对某些金属来说低至环境温度。我们发现，低温下塑性变形产生的纳米级纯铜和镍晶粒在临界晶粒尺寸以下表现出显著的热稳定性。晶粒尺寸越小，纳米晶粒的不稳定温度就越高，即使高于粗晶粒的再结晶温度，纳米晶粒也保持稳定。纳米晶粒固有的热稳定性源于在塑性变形过程中部分位错激活导致的晶界向低能态的自主演化。
The limitation of nanograined materials is their strong tendency to coarsen at elevated temperatures. As grain size decreases into the nanoscale, grain coarsening occurs at much lower temperatures, as low as ambient temperatures for some metals. We discovered that nanometer-sized grains in pure copper and nickel produced from plastic deformation at low temperatures exhibit notable thermal stability below a critical grain size. The instability temperature rises substantially at smaller grain sizes, and the nanograins remain stable even above the recrystallization temperatures of coarse grains. The inherent thermal stability of nanograins originates from an autonomous grain boundary evolution to low-energy states due to activation of partial dislocations in plastic deformation.