SEDL / STP / STP569-EB / STP33174S

Fatigue Behavior of an Ag³Mg-AgMg Eutectic Composite

Kim, YG
research associate, National Aeronautics and Space Administration, Lewis Laboratory, Cleveland, Ohio

Maurer, GE
Graduate assistant and professor, Rensselaer Polytechnic Institute, Troy, N. Y.

Stoloff, NS
Graduate assistant and professor, Rensselaer Polytechnic Institute, Troy, N. Y.

Pages: 16    Published: Jan 1975

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Abstract

The eutectic alloy Ag-32 atomic percent Mg has been directionally solidified at rates ranging from 0.8 to 27.7 cm/h to produce an aligned lamellar structure. The alloy, consisting of 40 volume percent AgMg and 60 volume percent of a solid solution of approximate composition Ag-27 atomic percent Mg, has been cycled in tension-tension loading at room temperature. Fatigue life increased sharply with both higher growth speeds and with the introduction of long range order into the Ag-27 atomic percent Mg phase by post-solidification heat treatment. Fractographic examination revealed a marked change in crack path and striation morphology as order was produced. It is concluded that improvements in fatigue life with growth speed were a consequence of decreased interlamellar spacing and the resulting rise in tensile strength of the alloy.