The effect of particle size on the local strain distribution in advanced aluminium alloys

Abstract

The High Resolution Digital Image Correlation (HRDIC) technique was used to analyse the deformation pattern in the AA7021 alloy. Two different microstructures were induced by correlating the gold remodelling conditions with ageing conditions: peak-aged at 120°C for 2 weeks and over-aged at 280°C for 4.5 hours. As for the DIC software operation, an initial window size determines the operating system error, while a final window size and the amount of overlap affect the resolution of a HRDIC map. Therefore, the above-mentioned parameters (an initial window size, a final window size and the amount of overlap) were deliberately optimised before the test. As a result, it was concluded that the interaction between precipitates and dislocations are determined by the size of precipitates. The GP zone and the ŋ' phase in the peak-aged alloy are cut by dislocations and lead to strain localization at thick slip bands within a grain. On the other hand, the over-aged alloy with equilibrium phases (ŋ, T and S) shows wavy slip lines as a result of the dislocation bowing mechanism and homogeneous deformation within a grain. The unusual tensile behaviour in the peak-aged alloy can be explained by the multiple simultaneous effects of glide plane softening and the bowing mechanism near the coarse ŋ phases.

Date of Award	1 Aug 2017
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Joao Quinta Da Fonseca (Supervisor) & Philip Prangnell (Supervisor)