Jul 19, 2019

Breakthrough throws new light on alloys

Breakthrough throws new light on alloys

A Monash University study may have unlocked the secret to creating stronger, lightweight magnesium alloys for applications in the automobile and aerospace industries.    

Researchers from Monash University, CSIRO and Chongqing University discovered a pattern of alloying element segregation in twin boundaries by using atomic-resolution X-ray mapping at lower electron voltage than is usually applied.

Their findings were published in Nature Communications today.

Engineers are constantly seeking strong, lightweight materials for use in cars, planes and in high-speed vehicles to improve fuel efficiency, aerodynamics, speed and weight load.  

Monash University described the finding as significant, as the deformation of lightweight magnesium during thermomechanical processes and applications prevents those alloys from being used more widely in place of steel.

It also has implications for other light alloys such as aluminium and titanium.

“Lightweight magnesium has tremendous potential for energy-efficient and environmentally-friendly applications. But the segregation in these materials is prone to electron beam damage,” lead author Professor Jian-Feng Nie, from Monash University’s Department of Materials Science and Engineering, said.

“The electron beam damage is most severe when segregated solute atoms become a single atomic column. This impacts the formability, deformation behaviour and tension-compression strength of wrought magnesium products.

“We demonstrated that it’s possible to solve this difficulty by using atomic-resolution X-ray mapping at a much lower accelerating voltage of electrons [120kV] instead of 300kV, which is commonly used.

“We further discovered that the new segregation pattern increases the boundary pinning effect by more than 30 times, and switches the migration mechanism of the twin boundary from the commonly accepted mode to a new one.”

The researchers used a magnesium alloy comprising neodymium and silver as part of their study.

They found significant improvements in shear stress, by 33 times, and elastic strain limit occurred when the twin boundary was populated with neodymium and silver.

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