| To clarify the effects of microstructure on the change of mechanical properties and monotonic tensile fracture mode in the Cl alloy aged at 180℃, the detailed measurement of hardness, tensile strength, elongation and the observation of optical micrography, scanning electron micrography, transmision electron micrography and energy dispersive X-ray analysis has been carried out. In the peak aged, the Cl alloy has much better tensile strength than other alloys, such as 2090, 8090, 2020 and 7075 alloy but has lower elongation than 7075 and 2090 alloys. The fracture surface of Cl alloy show a transgranular dimple fracture mode in the under aged and show a sub-grain boundary intergranular fracture mode caused by the secondry crack along the sub-grain boundary in the peak aged. The Cl alloy, in the fracture surface, has (Al_xCu_yAg_z), (Al_xCu_yFe_z) and (Cu_xAl_yAg_z) type inclusions and U {T₁(Al₂CuLi) or Ω(?)} phase at the grain boundary, which strengthen the matrix. |
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