Microstructure, Mechanical Properties, Electric and Thermal Conductivity of the As-Extruded Al-(1.0 wt.% Zn + 0.5 wt.% Cu) Alloys ( = 1, 2 and 4).

In this research, effects of Zn and Cu content on microstructure, mechanical properties, electric and thermal conductivity of the as-extruded Al-(Zn+0.5Cu) alloys were investigated. As the content of Zn and Cu increased, the area ratio of Al₂Cu intermetallic compounds increased. After homogenization treatment and extrusion process, most of Al₂Cu intermetallic compounds was disappeared due to solution in Al matrix of Cu atoms. As the (Zn+0.5Cu) content increased from 1 to 2 wt.%, the average grain size decreased remarkably from 645 to 227 m due to the dynamic recrystallization caused by the solute Zn and Cu atoms during the extrusion. With increasing Zn and Cu additions, the thermal conductivity was decreased from 225 ( = 1) to 208 ( = 2) and 183 W/mK ( = 4) due to electric scattering by solute Zn and Cu atoms. The ultimate tensile strength (UTS) of the as-extruded Al-(1Zn+0.5Cu) alloys improved remarkably from 77 ( = 1) to 142 MPa ( = 4) as Zn and Cu content increased, and the elongation increased from 30 to 33%. This improvement in the strength resulted from the grain refinement and solid solution strengthening due to the solute Zn and Cu atoms. The Zn and Cu addition in Al alloy played an important role in thermal conductivity and mechanical properties.