ALLOYING ALUMINUM WITH MAGNESIUM FOR DUCTILITY AT WARM TEMPERATURES (25 TO 250-DEGREES-C)

Solute additions generally increase flow stress and decrease ductility. However, in an earlier study which compared the tensile behavior of a commercial Al-4 pct Mg alloy (5182-0) relative to pure aluminum, the commercial alloy exhibited increases in both strength and ductility at elevated temperatures (<250°C). To more fully understand this unexpected behavior, a series of high purity Al-Mg alloys (0 to 6 wt pct) were tested over the same range of temperatures (25 to 250°C) and initial strain rates (10-4 to 10-1 s-1) as in the earlier study. At ambient temperature the Mg solutes decreased elongation while increasing flow stress, but as the temperature was increased to 250°C the elongation increased with Mg content. This increase in ductility accompanied the linear increases in strain-rate sensitivity which occurred with increasing amounts of Mg. Stress relaxation tests indicated that Mg solutes increase the amount of dynamic recovery occurring at elevated temperatures. These results are explained on the basis of an increased amount of vacancies in the Al-Mg alloys relative to pure aluminum. © 1979 American Society for Metals and the Metallurgical Society of AIME.