An experimental investigation

Alloy design based on single-principal-element systems has approached its limit for performance enhancements. A substantial increase in strength up to gigapascal levels typically causes the premature failure of materials with reduced ductility. Here, we report a strategy to break this trade-off by controllably introducing high-density ductile multicomponent intermetallic nanoparticles (MCINPs) in complex alloy systems. Distinct from the intermetallic-induced embrittlement under conventional wisdom, such MCINP-strengthened alloys exhibit superior strengths of 1.5 gigapascals and ductility as high as 50% in tension at ambient temperature. The plastic instability, a major concern for high-strength materials, can be completely eliminated by generating a distinctive multistage work-hardening behavior, resulting from pronounced dislocation activities and deformation-induced microbands. This MCINP strategy offers a paradigm to develop next-generation materials for structural applications.

Multicomponent intermetallic nanoparticles and superb mechanical behaviors of complex alloys

The purpose of this technical manuscript is to present an explanation of rapid solidification processing in an easily understandable manner so that the technique is widely accepted and put to commercial practice by many working in the industries of materials processing and manufacturing engineering. The comprehensive review article presents a comprehensive overview of the widely accepted and used rapid solidification processes. To better, understand rapid solidification in comparison with conventional solidification, the intrinsic aspects and types of nucleation and the kinetics governing nucleation and subsequent growth of the crystal during rapid solidification are presented and discussed. The commercially viable methods for the rapid solidification processing of metal-based and even intermetallic-based composites are presented. The technically viable methods for the consolidation of rapidly solidified powders are discussed. A succinct description of notable recent advances in the technique of spray processing is presented. In the last section of this article, we highlight the key findings of selected studies in the area of rapid solidification processing of advanced metallic, intermetallics, and composite materials that have helped to advance the processing technique for emerging applications that is synchronous with advances in technology.

The rapid solidification processing of materials: science, principles, technology, advances, and applications

Nano-lamellar materials with ultrahigh strengths and unusual physical properties are of technological importance for structural applications. However, these materials generally suffer from low tensile ductility, which severely limits their practical utility. Here we show that markedly enhanced tensile ductility can be achieved in coherent nano-lamellar alloys, which exhibit an unprecedented combination of over 2 GPa yield strength and 16% uniform tensile ductility. The ultrahigh strength originates mainly from the lamellar boundary strengthening, whereas the large ductility correlates to a progressive work-hardening mechanism regulated by the unique nano-lamellar architecture. The coherent lamellar boundaries facilitate the dislocation transmission, which eliminates the stress concentrations at the boundaries. Meanwhile, deformation-induced hierarchical stacking-fault networks and associated high-density Lomer-Cottrell locks enhance the work hardening response, leading to unusually large tensile ductilities. The coherent nano-lamellar strategy can potentially be applied to many other alloys and open new avenues for designing ultrastrong yet ductile materials for technological applications. Nano-lamellar materials with ultrahigh strengths are highly desirable for technological applications. Here the authors report a nanolamellar architecturing approach by utilizing coherent L12 structures to achieve ultrahigh strength and ductility in Ni-Fe-Co-Cr-Al-Ti multicomponent alloys.

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Ultrahigh strength and ductility in newly developed materials with coherent nanolamellar architectures.

Recent experimental work has been reviewed concerning the effects of grain boundary structure on grain boundary sliding and migration, and other boundary phenomena involved in high temperature plasticity. A basic knowledge of the structure-dependent intergranular phenomena is important for a full understanding of the heterogeneity and characteristic features of high temperature deformation and fracture, because the structural effects of grain boundaries enhance the boundary-induced heterogeneity of deformation and fracture in polycrystals. The grain boundary character distribution (GBCD) has been shown to be important and useful in explaining and controlling high temperature plasticity, superplasticity and fragility in polycrystals. The potential use of grain boundary design and control for high temperature materials has been discussed on the basis of recent work concerning GBCD, texture and other microstructural factors. The recent achievement of grain boundary design and control for high temperature materials has been briefly introduced.

Grain boundary design and control for high temperature materials

The physical and mechanical metallurgy of Ni3Al and its alloys is reviewed Emphasis is on developments within the past five years, a period of extremely rapid growth in research on the behaviour of this unusually interesting intermetallic compound This review is particularly concerned with solute effects on properties such as diffusion rates, ductility, fatigue resistance, and environmental stability, subjects that only recently have received much attention Novel processing techniques, including rapid solidification and powder processing, are shown to have played a key role in providing Ni3Al-base alloys with improved properties An assessment of needed areas of research to hasten commercial applications of Ni3Al alloys concludes the review

N. S. Stoloff

Papers

Physical and mechanical metallurgy of Ni3Al and its alloys