Time-dependent phase changes in Cu-rich amalgams.

Cu-rich amalgams represent a significant change in amalgam alloy formulations which may result in enhanced performance. Significantly, these systems reduce or eliminate the gamma2 phase. This work studied the phase changes which occurred from one hour to six months in 13 commercial amalgams by x-ray diffraction. This included 9 two-particle or blend systems and 4 single-particle systems. Gamma2 was found in all systems, but was reduced or eliminated on storage at 37 degrees C at rates which varied from system to system. During gamma2 elimination, the Cu6Sn5 content correspondingly increased, indicating that solid-state reaction occurs for up to six months in some systems.