Abstract
The effect of Cu addition on dispersoid precipitation, mechanical properties and creep resistance was investigated in an Al-Mn-Mg 3004 alloy. The addition of Cu promoted dispersoid precipitation by increasing the number density and decreasing the size of dispersoids. Metastable β′-Mg2Si and Q-AlCuMgSi precipitates were observed during the heating process and both could provide favorable nucleation sites for dispersoid precipitation. The addition of Cu improved the thermal stability of dispersoids during a long-term thermal holding at 350 °C for 500 h. Results of mechanical testing show that the addition of Cu remarkably improved the hardness at room temperature, as well as the yield strength and creep resistance at 300 °C, which was mainly attributed to dispersoid strengthening and Cu solid solution strengthening. The yield strength contribution at 300 °C was quantitatively evaluated based on the dispersoid, solid solution and matrix contributions. It was confirmed that dispersoid strengthening is the main strengthening mechanism in the experimental alloys.
Highlights
Al-Mn-Mg AA3xxx alloys are widely used in the automobile, packaging and architecture industries
By applying appropriate heat treatment [1,2,3,4], a number of α-Al(Mn,Fe)Si dispersoids could be precipitated in AA3xxx alloys
The α-Al(Mn,Fe)Si dispersoids have been proven to be thermally stable at 300 ◦ C [6], which is especially attractive to materials for elevated temperature applications
Summary
Al-Mn-Mg AA3xxx alloys are widely used in the automobile, packaging and architecture industries. AA3xxx alloys are strengthened by work hardening and are classified as non-heat-treatable alloys. By applying appropriate heat treatment [1,2,3,4], a number of α-Al(Mn,Fe)Si dispersoids could be precipitated in AA3xxx alloys. The α-Al(Mn,Fe)Si dispersoids are partially coherent with the aluminum matrix [1,5]. The strengthening effect of α-Al(Mn,Fe)Si dispersoids at ambient and elevated temperatures has been reported [1,6,7,8]. The α-Al(Mn,Fe)Si dispersoids have been proven to be thermally stable at 300 ◦ C [6], which is especially attractive to materials for elevated temperature applications
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