Trade-off Balancing between Strength and Toughness of Multi-Phase alloys containing Brittle Phases

系统地研究了在韧性基体中含有脆性金属间化合物相或在脆性金属间化合物基质中含有韧性相的合金的强度和韧性之间的权衡。所研究的合金系包括Nb-Si基合金、铁基铁素体合金、奥氏体型Fe-Mn-Al-C合金、铜合金和Al-Fe合金。Nb-Si合金由脆性的Nb_5Si_3和韧性的Nb固溶体相组成，呈混合片状形态，是燃气轮机发动机部件等超高温应用的候选材料。合金的高温强度和室温韧性都取决于片层组织的形态和间距。在考虑了脆性基体中延性相增韧机理的基础上，提出了一种优化折衷性能的方法，并对以Laves相为增强剂的Fe-Cr基铁素体合金和以E2型金属间化合物的析出实现强化的Fe-Mn-Al-C合金进行了类似的研究。在这两种情况下，脆性相的形态随晶体取向的变化和两相之间的失配控制着合金的强度和韧性。本工作成功地提供了许多关于先进金属材料微观结构-机械性能的有价值的基本信息，有助于设计各种结构应用的合金。

Trade-off balancing between strength and toughness has been systematically investigated in alloys having brittle an intermetallic phase in a ductile matrix or having a ductile phase within the brittle intermetallic matrix. The systems investigated include Nb-Si base alloy, Fe-base ferritic alloys, an austenitic Fe-Mn-Al-C alloys, Cu-alloys and an Al-Fe alloy. The Nb-Si alloys consist of brittle Nb_5Si_3 and a ductile Nb solid solution phase in a mixed lamellar morphology, which is a candidate material for ultra-high temperature application such as components in gas-turbine engines. Both high temperature strength and room temperature toughness of the alloy depend on the morphology and spacings of the lamellar microstructure. A method for optimization of trade-off properties has been successfully suggested with a consideration on the toughening mechanism by the ductile phase in a brittle matrix.Similar investigation was made in the Fe-Cr base ferritic alloys in which the Laves phase is the strengthening agent, and also in Fe-Mn-Al-C in which the strengthening is achieved by the precipitation of E2_1-type intermetallic compound. In both cases change in morphology of the brittle phase in relation to the crystallographic orientation and misfit between two-phases control the strength and toughness, or ductility of the alloys.The present work successfully provides many valuable basic information on the microstructure-mechanical properties of advance metallic materials that helps in designing the alloys for various structural applications.