A high-performance material at extremely low temperatures
by Staff Writers
Beijing, China (SPX) Jan 07, 2019
Cryogenic material have a wide range of applications in our life, such as deep-space exploration, applied superconductors, and gas industry. With the development of space technology and fusion reactor field, producing high-performance materials in the extreme conditions, especially at very low temperatures, has become a more and more impending mission. However, it's still a big challenge to produce metals and alloys with high-strength (s_UTS>1GPa) and excellent ductility (e_f>60%) at extremely low temperatures.
As a fire-new material, high-entropy alloys (HEAs) exhibit an extremely-broad philosophy on how to combine elements. The potent mixture strategy makes the opportunity to find something new and exciting very high. In this circumstance, the service performance of high-entropy alloy under extremely condition inevitably becomes something we're curious about.
In this paper, the authors have assessed the mechanical response of the CoCrFeNi high-entropy alloy (see the results in Figure 1), and found that this alloy exhibit a high ultimate tensile strength of 1.26 GPa and elongation to failure of 62% at 4.2 K, which are the best among almost all of metallic materials, as shown in Figure 2.
This study witnesses the extensive deformation twinning and phase transformation from a face-centered cubic (FCC) structure to a hexagonal close-packed (HCP) structure are responsible for the superior mechanical performance at such low temperature.
Moreover, the serration feature appears in the stress-strain curves of this alloy at liquid-helium temperatures and the authors deduce the high-density twinning and phase transformation contribute to the serration feature, and that the FCC-HCP transition makes the serrated flow unstable.
The results of high-mechanical performance at low temperatures, phase transition, and serration, not only exhibit a significant breakthrough in the fundamental materials science, but also indicate HEAs' tremendous prospects and potential applications in the field of extreme cryogenic engineering.
Give it the plasma treatment: strong adhesion without adhesives
Osaka, Japan (SPX) Dec 27, 2018
Polymers containing plastics are essential in modern life. Being lightweight, strong and unreactive, a vast range of technologies depend on them. However, most polymers do not adhere naturally to other materials, so they need adhesives or corrosive chemical treatments to be attached to other materials. This is a problem in areas like food and medicine, where contamination must be avoided at all costs. A clean way to make industrial polymers adhesive is urgently needed. Now, a team at Osaka Univers ... read more
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