Yield-point phenomena in substitutional alloys

Abstract
A material exhibits a yield point when a larger stress is required to initiate deformation by slip than to continue it. In a normal tensile test this is usually observed as a drop in load at the start of gross yielding. Load drops may also be observed that are due to deformation twinning, but this will not be discussed here. Annealed mild steel was once thought to be unique in showing an initial yield point but it is now known that the effect is quite general, and many examples occur in substitutional alloys.