Reaction of Silver-Tin Alloys and Mercury

¹ Department of Dental Materials, Marquette University School of Dentistry, Milwaukee, Wisconsin

The reactions between mercury and alloys of the silver-tin system have been studied by metallographic examination, determination of microindentation hardness and by X-ray diffraction studies.

Silver-rich alloys of the silver-tin system, when exposed to mercury, exhibited a surface reaction to form the silver-mercury phase, Ag₂Hg₃. Limited diffusion occurred into the bulk of these alloys at 37° C.

Tin-rich alloys of the silver-tin system, when exposed to mercury, reacted completely throughout the matrix; when the ratio of Ag₃Sn to tin was high, zones of reaction at the surface of Ag₃Sn grains, as well as unreacted Ag₃Sn could be demonstrated in the tin-mercury matrix. At high tin content, where the ratio of Ag₃Sn to tin was low, complete reaction of the Ag₃Sn with mercury occurred, leaving a mixture of the silver-mercury and tin-mercury phases.

The data and evidence here presented suggest that further studies of the silver-tin equilibrium diagram are warranted to establish details of the diagram, particularly in the Ag₃Sn region which is of special dental interest.