It has been known for some time that trace additions ( 2 Sn phase formed, although a substantial refinement of the distributions is observed. In the case of Na additions, the number density of particles is increased by two orders of magnitude, resulting in hardening increment increases of 270%. The In+Li additions lead to increases of approximately one order of magnitude in number density and 150% increases in the hardening increment. The generality of the observed effects and the resulting hardening responses are discussed.
