[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

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Development of new metallic alloys for biomedical applications

Oxygen, one of the most abundant elements on Earth, often forms an undesired interstitial impurity or ceramic phase (such as an oxide particle) in metallic materials. Even when it adds strength, oxygen doping renders metals brittle1–3. Here we show that oxygen can take the form of ordered oxygen complexes, a state in between oxide particles and frequently occurring random interstitials. Unlike traditional interstitial strengthening4,5, such ordered interstitial complexes lead to unprecedented enhancement in both strength and ductility in compositionally complex solid solutions, the so-called high-entropy alloys (HEAs)6–10. The tensile strength is enhanced (by 48.5 ± 1.8 per cent) and ductility is substantially improved (by 95.2 ± 8.1 per cent) when doping a model TiZrHfNb HEA with 2.0 atomic per cent oxygen, thus breaking the long-standing strength–ductility trade-off11. The oxygen complexes are ordered nanoscale regions within the HEA characterized by (O, Zr, Ti)-rich atomic complexes whose formation is promoted by the existence of chemical short-range ordering among some of the substitutional matrix elements in the HEAs. Carbon has been reported to improve strength and ductility simultaneously in face-centred cubic HEAs12, by lowering the stacking fault energy and increasing the lattice friction stress. By contrast, the ordered interstitial complexes described here change the dislocation shear mode from planar slip to wavy slip, and promote double cross-slip and thus dislocation multiplication through the formation of Frank–Read sources (a mechanism explaining the generation of multiple dislocations) during deformation. This ordered interstitial complex-mediated strain-hardening mechanism should be particularly useful in Ti-, Zr- and Hf-containing alloys, in which interstitial elements are highly undesirable owing to their embrittlement effects, and in alloys where tuning the stacking fault energy and exploiting athermal transformations13 do not lead to property enhancement. These results provide insight into the role of interstitial solid solutions and associated ordering strengthening mechanisms in metallic materials. Ordered oxygen complexes in high-entropy alloys enhance both strength and ductility in these compositionally complex solid solutions.

Enhanced strength and ductility in a high-entropy alloy via ordered oxygen complexes

A Review on Biomedical Titanium Alloys: Recent Progress and Prospect

Microstructurally inhomogeneous composites: Is a homogeneous reinforcement distribution optimal?

Surface modification of titanium and titanium alloys: Technologies, developments, and future interests

Effects of degree of deformation on the microstructure, mechanical properties and texture of hybrid-reinforced titanium matrix composites

Microstructure evolution and superelastic behavior in Ti-35Nb-2Ta-3Zr alloy processed by friction stir processing

Influence of oxygen content on microstructure and mechanical properties of Ti–Nb–Ta–Zr alloy

The propose of this review was to summarize the advances in multi-scale surface technology of titanium implants to accelerate the osseointegration process The several multi-scaled methods used for improving wettability, roughness, and bioactivity of implant surfaces are reviewed In addition, macro-scale methods (eg, 3D printing (3DP) and laser surface texturing (LST)), micro-scale (eg, grit-blasting, acid-etching, and Sand-blasted, Large-grit, and Acid-etching (SLA)) and nano-scale methods (eg, plasma-spraying and anodization) are also discussed, and these surfaces are known to have favorable properties in clinical applications Functionalized coatings with organic and non-organic loadings suggest good prospects for the future of modern biotechnology Nevertheless, because of high cost and low clinical validation, these partial coatings have not been commercially available so far A large number of in vitro and in vivo investigations are necessary in order to obtain in-depth exploration about the efficiency of functional implant surfaces The prospective titanium implants should possess the optimum chemistry, bionic characteristics, and standardized modern topographies to achieve rapid osseointegration

Liqiang Wang

Papers

Surface modification of titanium and titanium alloys: Technologies, developments, and future interests

Effects of degree of deformation on the microstructure, mechanical properties and texture of hybrid-reinforced titanium matrix composites

Microstructure evolution and superelastic behavior in Ti-35Nb-2Ta-3Zr alloy processed by friction stir processing

Influence of oxygen content on microstructure and mechanical properties of Ti–Nb–Ta–Zr alloy

Multi-Scale Surface Treatments of Titanium Implants for Rapid Osseointegration: A Review