A lightweight strain glass alloy showing nearly temperature-independent low modulus and high strength

Abstract

Fast development of space technologies poses a strong demand for elastic materials that are lightweight, strong, but compliant to achieve high density of elastic energy storage, and such properties need to be temperature-insensitive in space environments [1][2][3][4] . However, existing materials do not meet this demand.Here we report a lightweight magnesium-scandium (Mg-21.3 at. % Sc) alloy meeting this demand. It is as light and compliant as organic-based materials like bones and glass ber reinforced plastics, but stronger than them [5][6][7] ; thus, it exhibits a record-high elastic energy density ~0.5 kJ/kg among various metallic and organic-based composite materials at a moderate stress level of 200 MPa 8,9 . Importantly, the performance can persist for 1 million stress cycles and over a wide temperature range from ambient to cryogenic temperatures. Its exceptional properties stem from a strain-glass transition. In-situ microstructure observations during cooling show strain-glass nanodomains continuously form from the matrix phase, which enables low modulus, high strength, fatigue-resistance, and temperature-insensitivity.The lightweight strain-glass Mg-Sc alloy may nd applications in space technologies and other elds such as orthopedics 1,9-11 . Main TextMagnesium alloys have the lowest density (ρ ~2 g/cm 3 ) among all metallic structural materials, being comparable with a number of organic-based natural or arti cial materials like bones, hard wood and glass ber reinforced plastics (GFRP) 6,7,12,13 . Therefore, they have the potential to be a solution to various lightweight elastic components in space technologies such as tires, springs and seals 1-3 . These applications require a high weight-speci c elastic energy density (i.e., elastic energy per unit weight) under a moderate stress level (e.g., ~200 MPa) 4,8,9 and such a property needs to be insensitive to temperature changes (e.g., 290-120 K in Mars) 4 . As the weight-speci c elastic density U is de ned as U=σ 2 /2ρE, where σ denotes the stress and E the elastic modulus, a promising candidate material needs to possess a combination of low density, low modulus and high strength, together with the property stability over a wide temperature range. However, existing Mg-alloys are challenged by a trade-off relation between elastic modulus and strength (see Fig. 1) [14][15][16][17][18][19][20][21][22][23][24][25][26] , which precludes achieving low modulus and high strength simultaneously; meanwhile the desired property stability over a wide temperature range is challenged by the inevitable hardening of metallic bonding with decreasing temperature.Recently, shape-memory effect and superelasticity have been reported in a Mg-20.5 at. % Sc (Mg-20.5Sc) shape-memory alloy (SMA), as a result of a martensitic transformation 27 . Although the large superelasticity provides a possibility for lightweight elastic energy storage, the Mg-20.5Sc alloy possesses the same drawbacks of other SMAs 28 -the inherent temperature sensitivity of superelasticity and thus a narrow wo...

A polymer-like ultrahigh-strength metal alloy

“…Over the past decades, signi cant efforts have been made to seek metal alloys with simultaneously high strength and low modulus [4][5][6][7][8][9][12][13][14][15][16][17] ; but an alloy showing both steel-like high yield strength (σ y >1 GPa) and polymer-like low modulus (E ~10 GPa) still remains unattainable. So far, several alloys based on shape memory alloys (SMA) 5,16,17 are reported to reveal 1 GPa-class high strength and a moderately low modulus E ~30 GPa, and a conventional Mg-Sc strain glass alloy 7 has recently been shown to possess a lower modulus E ~20 GPa but with a lower strength σ y ~0.3 GPa. Despite these efforts, existing alloys still fall into the conventional grey band of Fig.…”

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Futuristic technologies like morphing aircrafts and superstrong arti cial muscles are hinged on metal alloys being as strong as an ultrahigh-strength steel (with a high yield strength σ y >1 GPa) yet as exible as a polymer (with an ultralow elastic modulus E ~10 GPa) 1-3 . However, achieving such "strong yet exible" alloys has proven challenging [4][5][6][7][8][9] . The di culty lies in an inevitable trade-off between strength and exibility 5,8,10 , which precludes a high-strength alloy from being of polymer-like ultralow modulus.Here we report a Ti-50.8 at.% Ni strain glass alloy showing an unprecedented combination of an ultrahigh yield strength σ y ~1.8 GPa with a polymer-like ultralow elastic modulus E ~10.5 GPa, together with a superlarge rubber-like J-shaped elastic strain of ~8%.

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“…Futuristic technologies like morphing aircrafts and superstrong arti cial muscles are hinged on metal alloys being as strong as an ultrahigh-strength steel (with a high yield strength σ y >1 GPa) yet as exible as a polymer (with an ultralow elastic modulus E ~10 GPa) 1-3 . However, achieving such "strong yet exible" alloys has proven challenging [4][5][6][7][8][9] . The di culty lies in an inevitable trade-off between strength and exibility 5,8,10 , which precludes a high-strength alloy from being of polymer-like ultralow modulus.…”

Микро- И Наноразмерные Материалы С Высокой Энтропией

“…И действительно, разработки авторов [11][12][13] эквиатомных или почти эквиатомных ВЭС вызвали необычайную заинтересованность исследователей в улучшении рабочих характеристик ВЭС для использования их в различных областях материаловедения в том числе в водородных технологиях. Так в области водородных технологий удалось реально повысить характеристики прочности и пластичности хладостойких сплавов при криогенных температурах [14,15], а также износостойкости мембранных сплавов при повышенных температурах (от 400°C до 770°C) [16,17].…”