Dual-phase nanostructuring as a route to high-strength magnesium alloys

Abstract

It is not easy to fabricate materials that exhibit their theoretical 'ideal' strength. Most methods of producing stronger materials are based on controlling defects to impede the motion of dislocations, but such methods have their limitations. For example, industrial single-phase nanocrystalline alloys and single-phase metallic glasses can be very strong, but they typically soften at relatively low strains (less than two per cent) because of, respectively, the reverse Hall-Petch effect and shear-band formation. Here we describe an approach that combines the strengthening benefits of nanocrystallinity with those of amorphization to produce a dual-phase material that exhibits near-ideal strength at room temperature and without sample size effects. Our magnesium-alloy system consists of nanocrystalline cores embedded in amorphous glassy shells, and the strength of the resulting dual-phase material is a near-ideal 3.3 gigapascals-making this the strongest magnesium-alloy thin film yet achieved. We propose a mechanism, supported by constitutive modelling, in which the crystalline phase (consisting of almost-dislocation-free grains of around six nanometres in diameter) blocks the propagation of localized shear bands when under strain; moreover, within any shear bands that do appear, embedded crystalline grains divide and rotate, contributing to hardening and countering the softening effect of the shear band.

Preparation and Characterization of TiB2-(Supra-Nano-Dual-Phase) High-Entropy Alloy Cermet by Spark Plasma Sintering

“…The grain growth caused by high temperatures prevents the further improvement of the mechanical properties. The combined nanocrystalline-amorphous structure (the size of each phase is less than 10 nm) exhibits near-ideal strength at room temperature [28]. The so-called "supra-nano-dual-phase structure (SNDP)" agrees well with that in the liquid phase in the study.…”

“…As an advanced ceramic material, titanium diboride (TiB 2 ) has been widely applied in many fields, including cutting tools, high-temperature structural components, aluminum evaporation boats, conductive coatings, and armors in the military [1,2] due to its outstanding properties, which include its high melting point (3225 • C), hardness (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35), modulus (560 GPa), excellent wear resistance, high chemical stability, and good electrical and thermal conductivity [3,4]. However, because of the oxygen-rich layer (TiO 2 and B 2 O 3 ), strong covalent bonding, and low self-diffusion coefficient, it is difficult to sinter TiB 2 to full density [5,6], even with the assistance of pressure.…”

Nanotwinned and hierarchical nanotwinned metals: a review of experimental, computational and theoretical efforts

“…[58][59][60][61] Moreover, the electrical conductivity of NT bulk metals is similar to the conventional CG counterpart but much higher than NC metals. 22 NT structures lead to a significant variation of the electronic and optical properties of nanowires. [38][39][40][41][42] And they are also able to strengthen the face-centered diamond-cubic materials such as silicon, diamond and cubic boron nitride which has a crystal structure analogous to that of diamond.…”

“…13 Although nanocrystallization failed to surmount the common sense that strength and ductility are mutually exclusive, many other efforts have been made to explore strategies for simultaneously improving the strength and ductility of NC metals by designing the tunable nanostructures of materials in recent years. 14 Several approaches have been proposed, such as bimodal or multimodal grain-size distribution, [15][16][17][18] second-phase particle hardening, [19][20][21] dual-phase nanostructuring, 22 fabricating high dislocation density in deformation-induced martensitic transformation system, 23 introducing NT structures into nanosized grains 14,24,25 and the construction of gradient/hierarchical structures via surface mechanical grinding treatment (SMGT), 26,27 surface mechanical attrition treatment (SMAT), 28,29 pre-torsion 30 and uniaxial tension. 31 Inspired by the fact that strain localization can be suppressed in NC metal films adhesion with a ductile substrate under tension, 32,33 the delocalized effect induced fracture toughening is realized in multilayered steel sheets.…”

Corrosion resistance of the microarc oxidation coatings prepared on magnesium alloy

“…In light metal structural materials, magnesium alloys possess many excellent properties such as high specific strength, good electric conductivity and thermal conductivity, vibration damping, electromagnetic shielding, easy processing molding and recycling use [1]. Therefore, they have wide prospect in the fields of electronic industry, aerospace, automobile, biomedicine, etc.…”