of commercial and high-purity non-heat-treatablealuminum alloys are investigated in this work. It is found that both magnesium and manganesei ns olid solution give an early linear concentration dependence of the strengtha tagiven strain for commercial alloys. This deviates from highpurity AlMg binary alloys, where aparabolic concentration dependence is found. Mn in solid solution is found to give ac onsiderably higher strengthening effect per atom than Mg, both in terms of yield stress and initial work hardening rate. This strengthening effect is stronger comparing commercial grades to high-purity alloys. This enhanced strengthening is believed to be as ynergy or clustering effect caused by interaction betweenMnatoms and trace elements, probably silicon, in solid solution.

Since automotive heat exchangers are operated at varying temperatures and under varying pressures, both static and dynamic mechanical properties should be known at different temperatures. Tubes are the most critical part of the most heat exchangers made from aluminum brazing sheet. We present tensile test, stress amplitude-fatigue life, and creep-rupture data of six AA3XXX series tube alloys after simulated brazing for temperatures ranging from 293 K to 573 K (20°C to 300°C). While correlations between several mechanical properties are strong, ranking of alloys according to one property cannot be safely deduced from the known ranking according to another property. The relative reduction in creep strength with increasing temperature is very similar for all six alloys, but the general trends are also strong with respect to tensile and fatigue properties; an exception is one alloy that exhibits strong Mg-Si precipitation activity during fatigue testing at elevated temperatures. Interrupted fatigue tests indicated that the crack growth time is negligible compared to the crack initiation time. Fatigue lifetimes are reduced by creep processes for temperatures above approximately 423 K (150°C). When mechanical properties were measured at several temperatures, interpolation to other temperatures within the same temperature range was possible in most cases, using simple and wellestablished equations.

Since automotive heat exchangers are operated at elevated temperatures and under varying pressures, both static and dynamic mechanical properties should be known at the relevant temperatures. We have collected elevated-temperature tensile test data, elevated-temperature stress amplitude-fatigue life data, and creep-rupture data in a systematic fashion over the past years. For thin, soft, and braze-simulated heat exchanger tube materials tested inside closed furnaces, none of the well-established methods for crack detection and observation can be applied. In our contribution, we present a simple statistical method to estimate the time required for crack initiation.

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