Precipitation strengthening is one of the most promising methods to develop magnesium (Mg) alloys. However, the nerve-wracking fact is that the cast Mg alloys always have coarse second particles, which inevitably leads to a poor ductility. In this study, a novel nanoscale superlattice precipitate (NSP) with a superior strengthening effect is developed by rare-earth Er alloying. The newly-developed cast Mg-Y-Zn-Er alloy possesses a yield strength of 154 MPa, a tensile strength of 234 MPa, and a total elongation of ∼ 13%. The NSPs is systematically investigated, using transmission electron microscopy and first-principles calculations. The NSP with an average radius of 4 nm has a five periodic supercell structure enriched with Zn, Y, and Er atoms. The first-principles calculations indicate that Zn, Y, and Er atoms are apt to segregate on the (112¯1) plane. The excellent strength is contributed mainly by the ordering strengthening of the NSPs. The addition of Er enhances the multiplication of dislocations and the activation of ⟨c + a⟩ dislocation system during deformation, contributing to the ductility. © 2023 Elsevier Ltd

Achieving high strength in Mg alloys is usually accompanied by ductility loss. Here, a novel Mg97Y1Zn1Ho1 at.% alloy with a yield strength of 403 MPa and an elongation of 10% is developed. The strength-ductility synergy is obtained by a comprehensive strategy, including a lamella bimodal microstructure design and the introduction of nano-spaced solute-segregated 14H long-period stacking-ordered phase (14H LPSO phase) through rare-earth Ho alloying. The lamella bimodal microstructure consists of elongated un-recrystallized (un-DRXed) coarse grains and fine dynamically-recrystallized grains (DRXed regions). The nano-spaced solute-segregated 14H LPSO phase is distributed in DRXed regions. The outstanding yield strength is mainly contributed by grain-boundary strengthening, 18R LPSO strengthening, and fiber-like reinforcement strengthening from the nano-spaced 14H LPSO phase. The high elongation is due primarily to the combined effects of the bimodal and lamellar microstructures through enhancing the work-hardening capability. © 2022

Achieving high strength in Mg alloys is usually accompanied by ductility loss. Here, a novel Mg97Y1Zn1Ho1 at.% alloy with a yield strength of 403 MPa and an elongation of 10% is developed. The strength-ductility synergy is obtained by a comprehensive strategy, including a lamella bimodal microstructure design and the introduction of nano-spaced solute-segregated 14H long-period stacking-ordered phase (14H LPSO phase) through rare-earth Ho alloying. The lamella bimodal microstructure consists of elongated un-recrystallized (un-DRXed) coarse grains and fine dynamically-recrystallized grains (DRXed regions). The nano-spaced solute-segregated 14H LPSO phase is distributed in DRXed regions. The outstanding yield strength is mainly contributed by grain-boundary strengthening, 18R LPSO strengthening, and fiber -like reinforcement strengthening from the nano-spaced 14H LPSO phase. The high elongation is due primarily to the combined effects of the bimodal and lamellar microstructures through enhancing the work-hardening capability.& COPY; 2022 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Peer review under responsibility of Chongqing University

The effect of Ho addition on the oxidation behavior of Mg-Zn-Y-Ho alloys was investigated at 500 °C in air. The results show that Ho addition can improve the high-temperature oxidation resistance of Mg-3Y-2Zn-12Ho alloys. With the addition of 12 wt% Ho, the parabolic rate constant lowers by 75% as compared to that without Ho addition. The improvement of high-temperature oxidation resistance can be attributed to the formation of dense Ho2O3, which reduces the inward oxygen diffusion coefficient by 3 orders of magnitude as compared to Y2O3. Moreover, the addition of Ho element in the Mg-Y-Zn alloy remains excellent tensile properties. © 2023 Elsevier Ltd

The effect of Ho addition on the oxidation behavior of Mg-Zn-Y-Ho alloys was investigated at 500 degrees C in air. The results show that Ho addition can improve the high-temperature oxidation resistance of Mg-3Y-2Zn-12Ho alloys. With the addition of 12 wt% Ho, the parabolic rate constant lowers by 75% as compared to that without Ho addition. The improvement of high-temperature oxidation resistance can be attributed to the formation of dense Ho2O3, which reduces the inward oxygen diffusion coefficient by 3 orders of magnitude as compared to Y2O3. Moreover, the addition of Ho element in the Mg-Y-Zn alloy remains excellent tensile properties.

B4C/Al composites with a high B4C content of 30 wt% were successfully fabricated by hot pressing sintering followed by hot rolling. The influence of hot rolling on the microstructure, mechanical properties, anisotropy and the interfacial conditions of the B4C/Al composites were systematically investigated. The improvement of the interfacial Al2O3 nanoparticles distribution during hot rolling increased both the strength and ductility. After sintering of B4C/Al composites, some Al2O3 nanoparticles aggregated together at the interface between B4C and Al matrix, lowering the interface bonding strength between B4C and Al matrix. The Al2O3 nanoparticles dispersed into the Al grain interior after rolling, leading to a well bonding interface between B4C particles and the Al matrix. In addition, the dispersion of Al2O3 nanoparticles into the Al grain interior contributed to the strength through Orowan strengthening and ductility through the enhancement of dislocation storage ability. The strengthening and toughening mechanisms of the composites are discussed in detail. (C) 2022 Elsevier B.V. All rights reserved.

Multicomponent high-entropy alloys (HEAs) can be tuned to a simple phase with some unique alloy characteristics. HEAs with body-centered-cubic (BCC) or hexagonal-close-packed (HCP) structures are proven to possess high strength and hardness but low ductility. The faced-centered-cubic (FCC) HEAs present considerable ductility, excellent corrosion and radiation resistance. However, their strengths are relatively low. Therefore, the strategy of strengthening the ductile FCC matrix phase is usually adopted to design HEAs with excellent performance. Among various strengthening methods, precipitation strengthening plays a dazzling role since the characteristics of multiple principal elements and slow diffusion effect of elements in HEAs provide a chance to form fine and stable nanoscale precipitates, pushing the strengths of the alloys to new high levels. This paper summarizes and review the recent progress in nanoprecipitate-strengthened HEAs and their strengthening mechanisms. The alloy-design strategies and control of the nanoscale precipitates in HEAs are highlighted. The future works on the related aspects are outlined.