#twinning deformation

Simultaneous high strength and large ductility are always desirable for metallic materials. However, while the strength of metals and alloys can be easily increased by five to 15 times through simple plastic deformation or grain refinement down to the nano-scale, the gain in strength is usually accompanied by a drastic loss of uniform ductility. Ductility depends strongly on the work hardening ability, which becomes weak in materials with high strength, especially in a single-phase material.

Publishing online in PNAS, the research group of Prof. WU Xiaolei at the Chinese Academy of Sciences, in collaboration with Prof. En Ma at Johns Hopkins University, U.S., have demonstrated a strategy for exploiting a dynamically reinforced multilevel heterogeneous grain structure (HGS). They demonstrated the behavior of such an HGS using the face-centered-cubic CrCoNi medium-entropy alloy (MEA) as a model system.

Back stress hardening is usually not obvious in single-phase homogeneous grains. To overcome this, the scientists purposely created an unusually heterogeneous grain structure. They took advantage of the low stacking fault energy of the MEA, which facilitates the generation of twinned nano-grains and stacking faults during tensile straining, dynamically reinforcing the heterogeneity on the fly.

Purdue University researchers have developed a superstrong material that may change some manufacturing processes for the aerospace and automobile industries.

The Purdue team, led by Xinghang Zhang, a professor in Purdue’s School of Materials Engineering, created high-strength aluminum alloy coatings. According to Zhang, there is an increasing demand for such materials because of their advantages for automakers and aerospace industries.

“We have created a very durable and lightweight aluminum alloy that is just as strong as, and possibly stronger than, stainless steel,” Zhang said. “Our aluminum alloy is lightweight and provides flexibility that stainless steel does not in many applications.”

Another member of the Purdue team, Yifan Zhang, a graduate student in materials engineering, said the aluminum alloy they created could be used for making wear- and corrosion-resistant automobile parts such as engines and coatings for optical lenses for specialized telescopes in the aerospace industry.