at% and wt%

Including: Atomic Percent, Atomic Percentage, Weight Percent, Weight Percentage

With regard to phase diagrams, percentages are used to show the relative proportions of elements in an alloy. The percentage is not shown for the first element, but is shown for subsequent elements in the alloy, for example Cu-27wt%Al is an alloy of Copper and Aluminium containing 27wt% Aluminium (and therefore 73wt%Copper). As different elements weigh different amounts the type of percentage is often shown to avoid confusion.

Simple equations enable you to convert between at% and wt%

• at% signifies atomic percentage, so Cu-27at%Al would have 27% of the atoms in the alloy as Aluminium and 73% of the atoms in the alloy as Copper.
  
• wt% signifies weight percentage, so Cu-27wt%Al would have 27% of the weight of the alloy as Aluminium and 73% of the weight of the alloy as Copper

Associated terms: Phase Diagram, Alloy