Quantitative metallography of precipitating and secondary phases after strengthening treatment of net shaped casting of Al-Zn-Mg-Cu (7000) alloys

The effect of a near net shaped casting of the Al-Zn-Mg-Cu (Al-7000) alloys on the size and distribution of the strengthening precipitates formed during the peak age (T6) heat treatment was investigated using analytical microscopy with SEM, XRD and high resolution TEM. The near net shaped components were produced using the Controlled Diffusion Solidification (CDS) technology coupled with the tilt pour gravity casting process. Three different alloys were selected from the Al-Zn-Mg-Cu family with three distinctive sum total of alloying elements (Zn +Mg + Cu = 4.3, 7.7 and 10.6 wt%). The uniaxial tensile yield strengths of these CDS cast alloys were also determined to be 279, 390 and 540 MPa, respectively. Further, the microstructural and uniaxial tensile properties of the CDS cast and wrought products of an Al-Zn-Mg-Cu alloy (AA7050) were also compared in this study.