Thermal Cycling under Constant Load to Low Temperatures of Aluminum and Magnesium Alloys

    Published: Jan 1961

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    The effect of thermal cycling under constant stress on aluminum alloys 7075-T6 and X2020-T6 and magnesium alloys AZ31B-H24 and HK31A-H24 was investigated for sawtooth type thermal cycling between −320 F and maximum temperatures of 200, 400, and 600 F for the aluminum alloys and 100 and 400 F for the magnesium alloys. The test equipment which permits thermal cycling under constant nominal stress by resistance heating of a specimen immersed in liquid nitrogen is described. Creep and creep rupture occurs on cycling at all these temperatures. For a given material under constant heating rate and thermal cycling range, the number of cycles to failure increases with decreasing nominal applied stress. Increase in the maximum cycle temperature displaces the σAN curves toward lower stress values. This decrease is roughly proportional to the decrease in ultimate isothermal tensile strength at Tmax. The effect of heating rate is not consistent. An analysis of the data shows that thermal cycling under constant load is basically an intermittent creep phenomenon and that failure can be predicted from the minimum plastic strain per cycle, ϵpc, according to Nϵpcn=constant, where n is close to unity.

    Author Information:

    Weiss, V.
    Associate Professor, Syracuse University, Syracuse, N. Y.

    Schaeffer, G. T.
    Graduate Research Assistant, Syracuse University, Syracuse, N. Y.

    Saule, A.
    Graduate Research Assistant, Syracuse University, Syracuse, N. Y.

    Sachs, G.
    Professor, Syracuse University, Syracuse, N. Y.

    Committee/Subcommittee: E28.10

    DOI: 10.1520/STP46975S

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