Discovery of anomalous softening phenomenon and shear bands suppression effect in metallic glass

Nov 15, 2012

A research team from Japan has discovered an anomalous softening effect in metallic glass, in which the hardness and elastic modulus of the material are reduced remarkably by applying giant shear strain to metallic glass under a high pressure of 5GPa. This research revealed that the shear zones generated in metallic glasses during room temperature deformation are suppressed accompanying this anomalous softening.

Metallic glasses are a type of amorphous metallic material and have excellent properties, such as high strength, high , soft magnetism, etc. in comparison with ordinary metals. Metallic glasses display these favorable properties because they do not have a like that of crystalline metallic materials, and therefore do not have the dislocations and associated with crystal structures. Utilizing these excellent properties, metallic glasses have already been applied to , golf clubs, projection materials for use in shot peening, etc. However, their range of applications had been limited, as metallic glasses lack ductility and are prone to localized deformation when deformed at room temperature.

Using the nanoindentation method, the team headed by Dr. Tsuchiya investigated the changes in the mechanical properties of a disk-shaped specimen of Zr50Cu40Al10 metallic glass when shear strain was applied by the high pressure torsion (HPT) method, in which giant torsional straining is applied under a high pressure of 5GPa at room temperature. As a result, the hardness and modulus of elasticity decreased as deformation increased, and after 50 revolutions of HPT straining, the hardness and elastic modulus of the specimen were markedly decreased to 22% and 30% of the values before straining, respectively. This is attributable to the phenomenon of "structural rejuvenation," in which the structure of the becomes more liquid-likeunder HPT.

Furthermore, when the indentation marks after nanoindentation were observed by scanning probe microscopy (SPM), numerous shear bands could be seen in the area around the indents before straining, but the number of shear bands decreased with increasing HPT straining, and no shear bands were observed after 50 revolution of HPT straining. This shows that localized deformation is suppressed by HPT straining, and the material undergoes a transition to a more homogeneous deformation mode. This discovery suggests the possibility of room temperature formingof metallic glasses, and is considered to enable development of applications to micro-to-nano systems, etc.

These results were published in Applied Physics Letters dated September 20, 2012.

Explore further: Wild molecular interactions in a new hydrogen mixture

More information: apl.aip.org/resource/1/applab/… 21914_s1?bypassSSO=1

add to favorites email to friend print save as pdf

Related Stories

New glass tops steel in strength and toughness

Jan 10, 2011

(PhysOrg.com) -- Glass stronger and tougher than steel? A new type of damage-tolerant metallic glass, demonstrating a strength and toughness beyond that of any known material, has been developed and tested ...

Metallic Glass Yields Secrets Under Pressure

Mar 16, 2010

(PhysOrg.com) -- Metallic glasses are emerging as potentially useful materials at the frontier of materials science research. They combine the advantages and avoid many of the problems of normal metals and ...

Recommended for you

Cold Atom Laboratory creates atomic dance

7 hours ago

Like dancers in a chorus line, atoms' movements become synchronized when lowered to extremely cold temperatures. To study this bizarre phenomenon, called a Bose-Einstein condensate, researchers need to cool ...

Wild molecular interactions in a new hydrogen mixture

13 hours ago

Hydrogen—the most abundant element in the cosmos—responds to extremes of pressure and temperature differently. Under ambient conditions hydrogen is a gaseous two-atom molecule. As confinement pressure ...

Scientists create possible precursor to life

14 hours ago

How did life originate? And can scientists create life? These questions not only occupy the minds of scientists interested in the origin of life, but also researchers working with technology of the future. ...

User comments : 0