Microstructure and Mechanical Properties of Spray-formed High Zn-containing Al-Zn-Mg-Cu alloy

High Zn-containing aluminum (Al) alloy AA7034 was prepared by spray forming rapid solidification technique, and studied for microstructural development and mechanical properties during subsequent hot extrusion and heat treatment processing. It is found out that microstructure after spray forming is composed of equiaxed grains with an average grain size of about 40 μm; however, porosity appears in the spray-formed material. The hot extrusion results in the elimination of microporosity and alignment of microstructure along the extruded direction. The intermetallic compound MgZn2 is detected as a main secondary phase, in an expansion form Mg(Zn,Cu,Al)2, at the spray-formed and extruded states as discovered by XRD; however, impurity phase Al7Cu2Fe is revealed additionally through EDS analysis. The alloy exhibits excellent strength at the peak-aged condition (T6) with Vickers microhardness and tensile strength values of 218 and 808MPa, respectively; which is ascribed to the increased volume fraction of hardening precipitates because of extra Zn-dissolution in the spray forming process.