The shield of Captain America

posted by @ulaulaman #physics #chemistry #superhero #CaptainAmerica

After the releasing of the movie Captain America: The first Avenger in 2011 by Paramount Picture, Suveen N. Mathaudhu, the Program Manager responsible for Synthesis and Processing of Materials at the U.S. Army Research Office in Durham, NC, written a brief article, The Making of Captain America's Shield (pdf), where he try to understand if today we have the ability to construct the Captain America's shield. Thanks to Lynne Robinson⁽¹⁾ and the Avengers movie, Mathaudhu and his little review returned to the attention of people.
First of all we try to resume the story of the Cap's shield. The first comics shield was a triangular shield but starting from Captain America Comics #2 (april 1941), Cap was equipped by the most famous circular shield:

A concavo-convex metal disc approximately 0.76 m in diameter, it is virtually indestructible and has remained his most constant shield over the decades.

Following Captain America #255 (march 1981), the shield was presented to Rogers by president Franklin Roosevelt⁽⁶⁾.

It is created by the scientist Myron MacLain during some experiments with vibranium, an extraterrestrial metal introduced in Fantastic Four #53 with the ability to absorb vibrations⁽⁶⁾. A useful utilization of the vibranium was made by Thor in Avengers #68 in order to contain the explosion of Ultron-6⁽⁵⁾.

During the same saga (started on Avengers #66), MacLain presented for the first time the adamantium⁽⁶⁾. This metal was created (or founded) by MacLain some years after the creation of Cap's shield: this last was made by an alloy of vibranium and steel with an unkown catalyst; so MacLain try to reproduce that experiment and he accidentaly created adamantium, like the same metallurgist telled in Captain America #303.

This is the comics story of Captain America's shield, and so we are right to start our journey in the material science of our real world. And we start with a very resistant metallic glass:

Owing to a lack of microstructure, glassy materials are inherently strong but brittle, and often demonstrate extreme sensitivity to flaws. Accordingly, their macroscopic failure is often not initiated by plastic yielding, and almost always terminated by brittle fracture. Unlike conventional brittle glasses, metallic glasses are generally capable of limited plastic yielding by shear-band sliding in the presence of a flaw, and thus exhibit toughness–strength relationships that lie between those of brittle ceramics and marginally tough metals. Here, a bulk glassy palladium alloy is introduced, demonstrating an unusual capacity for shielding an opening crack accommodated by an extensive shear-band sliding process, which promotes a fracture toughness comparable to those of the toughest materials known. This result demonstrates that the combination of toughness and strength (that is, damage tolerance) accessible to amorphous materials extends beyond the benchmark ranges established by the toughest and strongest materials known, thereby pushing the envelope of damage tolerance accessible to a structural metal.⁽²⁾

The second stop is the creation of two new alluminium alloys, more strenght than pervious alloys:

It is the focus of present research to extend the strength of commercially valuable alloys without sacrii cing ductility by engineering nanoscale microstructures or nanostructures. If conventional thermomechanical processing of age-hardenable Al alloys results in a material dominated by dispersions of microscale, solute-rich precipitates, what is the result when SPD is used to engineer nanoscale structures? Furthermore, what relationships would such nanostructures have to the materials properties?
(...) In this study we present a new 7075 Al alloy that expands the known limits of mechanical property performance and provide a comprehensive atomic level investigation of the structure using new high-resolution characterization techniques for both nanostructured alloys [the other alloy is 5083 Al] (...) and both alloys contain a solid solution, free of precipitation, featuring
(i) a high density of dislocations,
(ii) subnanometre intragranular solute clusters,
(iii) two geometries of nanometre-scale intergranular solute structures and
(iv) grain sizes tens of nanometres in diameter.
Our results demonstrate that this novel architecture of ers a design pathway towards a new generation of super-strong materials with new regimes of propertyperformance space.⁽³⁾

And finally:

(...) computational materials science for process simulation and design has been tremendously enhanced with the meteoric growth of computing power and speed. The worldwide acceleration of integrated computational materials engineering (ICME) has enabled more detailed understanding of the complex effects of processing on the resultant microstructures, and thus the enhanced properties.⁽⁴⁾

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News: newswise | msnbc

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(1) Lynne Robinson (2012). The Super Materials of the Super Heroes Journal of the Minerals, Metals and Materials Society, 64 (1), 13-19 DOI: 10.1007/s11837-012-0256-x
(2) Marios D. Demetriou, Maximilien E. Launey, Glenn Garrett, Joseph P. Schramm, Douglas C. Hofmann, William L. Johnson, Robert O. Ritchie (2011). A damage-tolerant glass Nature Materials (10), 123-128 DOI: 10.1038/nmat2930
(3) Peter V. Liddicoat, Xiao-Zhou Liao, Yonghao Zhao, Yuntian Zhu, Maxim Y. Murashkin, Enrique J. Lavernia, Ruslan Z. Valiev, Simon P. Ringer (2010). Nanostructural hierarchy increases the strength of aluminium alloys Nature Communications (1) DOI: 10.1038/ncomms1062 (pdf)
(4) Suveen N. Mathaudhu, The Making of Captain America's Shield (pdf)
(5) SuperMegaMonkey's Marvel Comics Cronology: Avengers #66-68
(6) Brian Cronin. When we first met #22