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Molecular dynamics simulations were utilized to investigate the mechanical properties of the Al–Co–Cr–Fe–Ni high-entropy alloy and observe atomic microstructure and internal dislocation line changes under different parameter conditions. The findings demonstrate that the mechanical properties of the AlCoCrFeNi3 high-entropy alloy are significantly superior to those of conventional alloys in ambient temperature. During the tensile process, the face-centered structure undergoes interconversion with other structure types, while the internal dislocation lines gradually increase. The presence of grain boundaries impedes dislocation movement, resulting in lower deformation capacity and tensile strength in polycrystals compared to single crystals. Enhancing Ni content, increasing strain rate, and decreasing temperature during tensile process contributes to the enhancement of the mechanical properties of material. Among these factors, the Ni content exerts the most significant influence on the mechanical properties of the material. [ABSTRACT FROM AUTHOR]

Friction stir welding was utilized to obtain high-quality SUS301L stainless steel joints, whose mechanical and corrosion properties were thoroughly evaluated. Sound joints were obtained with a wide range of rotational velocities from 400 to 700 rpm. The microstructures of the stir zone primarily consisted of austenite and lath martensite without the formation of detrimental phases. The ultimate tensile strength of the welded joints improved with higher rotational velocities apart from 400 rpm. The ultimate tensile strength reached 813 ± 16 MPa, equal to 98.1 ± 1.9% of the base materials (BMs) with a rotational velocity of 700 rpm. The corrosion resistance of the FSW joints was improved, and the corrosion rates related to uniform corrosion with lower rotational velocities were one order of magnitude lower than that of the BMs, which was attributed to the lower martensite content. However, better anti-pitting corrosion performance was obtained with a high rotational velocity of 700 rpm, which was inconsistent with the uniform corrosion results. It could be speculated that a higher martensitic content had a negative effect on the uniform corrosion performance, but had a positive effect on the improvement of the anti-pitting corrosion ability. [ABSTRACT FROM AUTHOR]

Nanotwinned exist in crystals as coherent interfaces with low interfacial energy, which can not only improve the strength of metal materials, but also increase the ductility. In this manuscript, we have performed molecular dynamics simulations of the mechanical properties of a nano-columnar crystalline Cu-Ni alloy with different twin boundary spacing. It is found that the model without twin has a stacking fault tetrahedron composed of stair-rod dislocations, which results in a small change in dislocation density at the later stage of deformation, and the average stress after yielding is lower than that of the model with twin. During the deformation process, with the increase of Other atoms, the dislocation slip barrier is enhanced, the tensile strength is increased, and the yield phenomenon is delayed, which is more obvious with the decrease of twin boundary spacing. The dislocation density decreases with the decrease of the spacing of the twin boundary, and the dislocation segments become shorter. When the twin boundary spacing is 0.625 nm, the tensile strength is increased by about 71% compared with the model without twin structure. [ABSTRACT FROM AUTHOR]

The influence of microstructures (bimodal and basketweave) on the tensile properties and deformation mechanism of Ti-5Al-1V-1Sn-1Zr-0.8Mo alloy was investigated via an in situ tensile test monitored by electron backscatter diffraction (EBSD)-assisted slip trace analysis. The bimodal structure exhibited good plasticity, but its tensile strength was lower than that of the basketweave structure. These variations could be attributed to the larger α colony structure in the basketweave structure. In situ tensile testing showed that the α colony in the basketweave structure can promote the formation of shear bands, leading to decreased plasticity. The activation of numerous slip systems in αp of the bimodal structure ensured good plasticity. Meanwhile, deformation twins were occasionally observed in the bimodal structure. However, dislocation slip and deformation twins were observed inside the large-sized grain boundary α (αGB) phase in the basketweave structure. The results of this study can extend the potential application of Ti alloys. [ABSTRACT FROM AUTHOR]

Metal matrix composites have been developed to overcome the urgent demand of light-weight design. High entropy alloys (HEAs) are newly emerged as a new kind of potential reinforcement for metals due to their outstanding physical and mechanical properties. Here, a kind of novel Al matrix composite reinforced by Al 0.8 CoCrFeNi HEA particles was fabricated by multi-pass friction stir processing (FSP). The incorporated HEA particles were homogeneously distributed into the composites and maintained the structural integrity. The average grain size of the FSPed composites decreased from 4.6 μm of Al matrix to 2.8 μm due to the particle-stimulated nucleation mechanism. The hardness, yield strength and ultimate tensile strength of the FSPed composites increased by 56%, 42% and 22% than that of the FSPed Al matrix with no obvious decrease of elongation. Interfacial diffusion occurred and the interfacial region is confirmed to be the Al 3 CoCrFeNi rather than the intermetallic phases. HEA particles have great potentials in mechanical properties enhancement for conventional light-weight alloys. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP) was utilized to fabricate high strength and ductility Mg–6Zn alloys via the co-alloying of 1.0 Y and 0.5 Zr elements. The effect of co-alloying on microstructure and mechanical properties of the as-casted and FSPed Mg alloys were evaluated. Grain refinement and second-phase increase via co-alloying were obtained. The increased second-phases contributed to dynamic recrystallization and weakened the basal texture through heterogeneous nucleation. The yield strength, ultimate tensile strength and elongation of the FSPed Mg–6Zn–1Y-0.5Zr alloys reached 170 MPa, 310 MPa and 27.7%, which enhanced by 27.8%, 10.7% and 48.9% than the FSPed Mg–6Zn alloys. Grain refinement, dispersion strengthening and the tailored texture are responsible for the enhancement of mechanical properties. The Mg–Zn series alloys with trace Y and Zr co-addition are confirmed to be promising for developing rare-earth containing Mg alloys with outstanding mechanical performance and acceptable cost. [ABSTRACT FROM AUTHOR]

Abstract A novel technique named friction filling staking joining (FFSJ) was proposed to join 6082-T6 aluminum alloy and poly propylene (PP) polymer sheets. The FFSJ was realized with the filling of a pre-fabricated hole using an additional filling stud. The excellent FFSJ joint was achieved under the synthesis effects of frictional heat and thermo-mechanical behavior at the interface between the filling stud and polymer sheet. The intimate joining formed at the interface, while the pre-fabricated hole was completely filled with the stud. A macro mechanical interlocking formed between the metal and filling stud, attributing to the main joining mechanism. And the partial adhesive layer appeared between the re-solidified polymer and metal. The maximum tensile shear strength was comparable to that of state-of-the-art welding. The FFSJ combines the benefits of the improvement of assembly precision, simple process, short welding cycle and high strength compared with the state-of-the-art welding, indicating that the FFSJ technique has potential to join metal with polymer or polymer matrix composites. Graphical abstract Image 1 Highlights • Friction-based filling stacking joining (FFSJ) of metal and polymer is proposed. • Adhesive bonding and mechanical interlocking attribute to joining mechanism. • Shear tensile strength of FFSJ is comparable to the state-of-the-art welding. [ABSTRACT FROM AUTHOR]

• Non-weld-thinning friction stir welding was proposed. • An adjustable tool with inner and outer shoulders was employed. • Smooth surface without weld thinning was achieved. • The theory of "single welding, double forming" was proposed. • The ultimate tensile strength reached 91% of base metal. Weld thinning has been an inherent issue of friction stir welding, which is detrimental to the joint integrity and mechanical properties especially for thin structures. In this paper, a novel method named non-weld-thinning friction stir welding was proposed. The welding tool contained an inner shoulder and an outer shoulder, and it was adjustable to control the protrusion of inner shoulder relative to outer shoulder. The outer shoulder could accumulate and refill the overflowing materials to eliminate weld thinning. The ultimate tensile strength reached 91% of base metal, which indicated that non-weld-thinning friction stir welding had the feasible and potential to realize high quality joint without weld thinning. [ABSTRACT FROM AUTHOR]

Despite great strengthening potential of graphene nanoplatelets (GNPs) reinforced aluminum matrix composites, sparked with its high performance with extremely low additions of GNPs, the fatal ductility loss of this composites restricts its applications. The key to obtaining the composites with high comprehensive mechanical performance is the uniformly intragranular dispersion of strengthening phase and the ultrafine microstructures. Here, we present a strategy for GNPs reinforced aluminum composites, namely deformation-driven metallurgy. Multiscale nanostructures were achieved with the structure of nano Al 2 O 3 dots-GNPs-aluminum matrix, while the vast majority of GNPs were dispersed inside grains uniformly and formed metallurgical bonding with the matrix. Nano-grained microstructure was obtained by the "negative feedback" controlled low heat input and the isolation of the GNPs during dynamic recrystallization. An enhancement of tensile strength by 317% with only 27% ductility loss was achieved, indicating that the deformation-driven metallurgy could provide a novel design strategy for GNPs reinforced aluminum composites. Image 1 [ABSTRACT FROM AUTHOR]