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.

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In this work, WC-10Co-4Cr coatings were separately deposited on 300M steel by high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) spraying processes. Microstructure, porosity, micro-hardness, bonding strength, wear and corrosion resistance of the coatings after different processing were investigated and compared. The result shows that dense and homogeneous microstructure existed in both two WC-10Co-4Cr coatings. Owing to lower temperature flames and higher particle velocity in the HVAF process, the HVAF-sprayed WC-10Co-4Cr coating exhibited less decarburisation, lower porosity (0.74%), higher micro-hardness (1162 HV 0.3 ) and bonding strength (74.68 MPa) than HVOF-sprayed WC-10Co-4Cr coating. In addition, wear and corrosion resistance of these two coatings were evaluated by sliding wear test and electrochemical corrosion test. The HVAF-sprayed WC-10Co-4Cr coating also exhibited excellent wear resistance and superior corrosion property than HVOF-sprayed WC-10Co-4Cr coating.

The precipitate transformation from NiAl-type to Ni 2 AlMn-type and its influence on the mechanical properties of the Fe-5Ni-1Al-xMn (x = 0, 1, 3, and 5 wt.%) alloys were studied thoroughly through a combination of three-dimensional atom probe tomography (APT), firstprinciples calculations and mechanical tests. APT reveals the precipitation of NiAl-type nanoparticles in the 0-3Mn alloys and the co-precipitation of fine NiAl-type and coarse Ni 2 AlMn-type nanoparticles in the 5Mn alloy, in which the Ni 2 AlMn-type nanoparticles are formed as a result of the coarsening of the NiAl-type ones. The first-principles calculations indicate that the Ni 2 AlMn-type nanoparticles are energetically more favorable than the NiAl-type ones, but their nucleation and growth kinetics are relatively slow, resulting in the initial precipitation of the NiAl-type nanoparticles and the later precipitate transformation from NiAl

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