So while I don’t have access to the journal article, this is likely what is called a High Entropy Alloy, or HEA. Basically how they work is that when enough metals are mixed in together in roughly equal quantities, no single element is the solute for the other element’s to dissolve into (how traditional metal alloys work). This causes the atomic lattice, how the atoms are stacked together, to alternate between Cr, Co, and Ni. This irregularity makes it really challenging for flaws (dislocations) to move through the material and thus makes it really difficult for the material to deform. In normal alloys, the dislocation movement is usually slowed and the material strengthened (higher max stress) by adding barriers to dislocation movement, such as grain boundary’s or additional dislocations to get tangled up in. Unfortunately while these make the material stronger, they usually decrease the toughness (roughly stress*strain) because once these barriers are hit there isn’t much more deformation (strain) to be had before the material fractures. Because HEA’s already have a higher energy cost to move dislocations, they are able to reach a higher stress before these other factors kick in to reduce the fracture strain, resulting in a much higher toughness.
While this makes HEA’s really cool in a variety of applications, they are really difficult to manufacture and need a REALLY high temperature and REALLY clean furnace to smelt. This limits the size of the ingots that can be produced, and so it is still a ways off for HEAs to be practical in many situations.
This is just my estimate from what the post has and my limited understanding of HEAs, so if any material scientists want to jump in and ream me please do.
forgetcows t1_j0h9cm1 wrote
Reply to Toughest material ever is an alloy of chromium, cobalt and nickel by tonymmorley
So while I don’t have access to the journal article, this is likely what is called a High Entropy Alloy, or HEA. Basically how they work is that when enough metals are mixed in together in roughly equal quantities, no single element is the solute for the other element’s to dissolve into (how traditional metal alloys work). This causes the atomic lattice, how the atoms are stacked together, to alternate between Cr, Co, and Ni. This irregularity makes it really challenging for flaws (dislocations) to move through the material and thus makes it really difficult for the material to deform. In normal alloys, the dislocation movement is usually slowed and the material strengthened (higher max stress) by adding barriers to dislocation movement, such as grain boundary’s or additional dislocations to get tangled up in. Unfortunately while these make the material stronger, they usually decrease the toughness (roughly stress*strain) because once these barriers are hit there isn’t much more deformation (strain) to be had before the material fractures. Because HEA’s already have a higher energy cost to move dislocations, they are able to reach a higher stress before these other factors kick in to reduce the fracture strain, resulting in a much higher toughness.
While this makes HEA’s really cool in a variety of applications, they are really difficult to manufacture and need a REALLY high temperature and REALLY clean furnace to smelt. This limits the size of the ingots that can be produced, and so it is still a ways off for HEAs to be practical in many situations. This is just my estimate from what the post has and my limited understanding of HEAs, so if any material scientists want to jump in and ream me please do.