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Heterogeneous precipitation behavior of Al Cu Mn alloy during solid solution and its contribution to high temperature strength

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Document pages: 12 pages

Abstract: Al xwt. Cu-1.0 wt. Mn alloy (x   =   2.0, 4.5 and 7.5) and its contribution to mechanical properties were studied by tensile test and microstructure characterization. There are primary defects in Al Cu Mn alloy α- The Al dendrite has a shell core structure, and the Cu content in the shell is higher than that in the core. With the increase of Cu content in the alloy, the area of shell region (Cu rich) increases. A large number of dispersed fine Al Cu Mn particles are precipitated in the solution. The alloy with low copper content can only precipitate TMN (al20cu2mn3) particles. However, in alloys with high copper content, alcu3mn2 particles were first found to precipitate next to TMN. However, this precipitation behavioris uneven. The precipitation zones in the solution microstructure are consistent with the Cu-rich regions in the as-cast microstructure. A number of fine particles (dozens nanometer in size) are first found to precipitate on the rod-like TMn particles during the aging phase. The redissolution and granulation of the eutectic CuAl2 phase during the solutionizing process result in the formation of particle-free bands between the precipitation zones. The tension test at 300°C demonstrates that the increase in high temperature strength is due to the dispersoid precipitation during solutionizing, and the precipitation behavior in the aging phase has little or no effect, however, largely improves the tensile strength at room temperature. High temperature strength is significantly increased with an increase in Cu content, which correlates to an increase in number and decrease in size of TMn and AlCu3Mn2 particles.

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