Effect of Mn Addition on the Mechanical Properties in Al-Cu-Li-Mg-Ag-Zr Alloys

The mechanical properties of Al–5%Cu–1.3%Li–0.4%Mg–0.4%Ag–1.16%Zr alloys without Mn and with 0.3%, 0.6% and 1.2% Mn have been investigated after the aging at the temperatures of 90, 150, 180, and 230 oC. With Mn addition the alloys show a good work-hardening property, and the elongation of alloys increases. With the 0.6% Mn the best elongation can be obtained. The strength of alloys with 0.3% or 1.2% Mn is lower than that of the alloy without Mn, whereas the strength of alloy with 0.6% Mn is almost same as that of the alloy without Mn. In the alloy with 0.6% Mn aged at 180 oC for 12 hours the optimum properties – combination of tensile strength and elongation, 620 MPa and over 12 %, respectively – are obtained. These favorable effects by a proper Mn addition are considered to come mainly from the Mn-dispersoid to prevent strain localization normally associated with the shearable precipitates.