Microstructure-Property Modelling and

The ever growing demands for high strength aluminium alloys in the aerospace industry have greatly enhanced the development of alloy chemistry and thermo-mechanical treatments for optimisation of mechanical and physical property balance of 7xxx series alloys. The main objective of this work is to provide an understanding of how compositional variations and ageing treatments affect the microstructure characteristics, strength and electrical conductivity balance whilst taking account of toughness for Al-Zn-Mg-Cu 7xxx A1 alloys. This thesis has investigated the effect of compositional variations on microstructure, electrical conductivity (which is a measure of stress corrosion resistance) and yield strength balance of a wide range of Zr-containing and Cr-containing 7xxx alloys. Twenty-two 7xxx A1 alloys within composition windows of 7010, 7x50 and 7x75 aerospace alloys have been studied and modelled. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM) along with energy dispersive X-ray spectrometry (EDS), and transmission electron microscopy (TEM) have been employed to study phase transformation, grain structure, coarse intermetallic particles of these alloys. This has provided useful information on alloy design and thermo-mechanical processing of high strength 7xxx alloys via microstructural control. To provide predictive tools for conductivity and yield strength, two physically based models for conductivity and yield strength have been presented in this thesis.