Ultrafine grained metals and metal matrix nanocomposites with enhanced strength and good tensile ductility for structural applications have been successfully fabricated by processing and thermomechanically consolidating powders and, in some cases, post-consolidation heat and thermomechanical treatments. This paper provides an overview of the substantial amount of research work mainly published by the author’s research groups rather than a comprehensive review of the vast amount of very active research work published in this area. The microstructures and tensile properties of the samples fabricated and the correlations between them strongly suggest that the synergistic effects of grain boundary strengthening and intragranular ceramic (and other hard) nanoparticles are highly desirable for significantly enhancing the tensile yield strength and maintaining generally good tensile ductility. The extra boundaries between hard regions and soft regions introduced by heterogeneous microstructure can further enhance the strength of the material without sacrificing tensile ductility by inducing back stress in the soft regions. However, these boundaries also induce forward stress in the hard regions which has a weakening effect on them and needs to be managed by dispersing nanoparticles in the hard regions or other means.

通过加工和热固结粉末，并在某些情况下进行后固结热处理和热机械处理，已成功制造出具有增强的强度和良好的延展性的，用于结构应用的超细晶粒金属和金属基质纳米复合材料。本文概述了主要由作者的研究小组发表的大量研究工作，而不是对该领域发表的大量非常活跃的研究工作进行了全面回顾。所制备样品的微观结构和拉伸性能以及它们之间的相关性强烈表明，为了显着提高拉伸屈服强度并保持总体良好的拉伸延展性，非常需要晶界强化和颗粒内陶瓷（和其他硬质）纳米颗粒的协同作用。由异质微观结构引入的硬区域和软区域之间的额外边界可以通过在软区域中引起反应力来进一步增强材料的强度，而不会牺牲拉伸延展性。但是，这些边界也会在硬区域中引起正向应力，从而对它们产生减弱作用，因此需要通过将纳米颗粒分散在硬区域中或通过其他方式进行处理。由异质微观结构引入的硬区域和软区域之间的额外边界可以通过在软区域中引起反应力来进一步增强材料的强度，而不会牺牲拉伸延展性。但是，这些边界也会在硬区域中引起正向应力，从而对它们产生减弱作用，因此需要通过将纳米颗粒分散在硬区域中或通过其他方式进行处理。由异质微观结构引入的硬区域和软区域之间的额外边界可以通过在软区域中引起反应力来进一步增强材料的强度，而不会牺牲拉伸延展性。但是，这些边界也会在硬区域中引起正向应力，从而对它们产生减弱作用，因此需要通过将纳米颗粒分散在硬区域中或通过其他方式进行处理。