Abstract
The strength and work hardening of age hardened AA6063 and AA6082 alloys have been investigated in terms of a detailed characterization of precipitate and dislocation structures obtained by TEM and SEM. Tensile and compression tests were performed at as quenched, peak aged and severely aged conditions. A strong work hardening in the as quenched condition was found, similar to AlMg alloys with twice as much alloying elements in solid solution. It was found that the initial work hardening rate and the critical failure strain are both smallest at the peak aged condition. During large deformations the needle-shaped precipitates are sheared uniformly by dislocations altering their <001> orientations, which indicates extensive cross slip. In the overaged condition the early initial work hardening is larger than at the peak aged condition, but followed by a weak linear work hardening, apparently directly entering stage IV at a low strain. Cracked, needle-shaped precipitates were seen at larger strains.
Highlights
Precipitation of thermodynamically metastable or stable phases in age-hardenable aluminium alloys enables design of a variety of strong and light alloys
The strength and work hardening of age hardened AA6063 and AA6082 alloys have been investigated in terms of a detailed characterization of precipitate and dislocation structures obtained by TEM and SEM
This alone results in a lower number density and volume fraction of precipitates in AA6063 T6, but it is responsible for a slower precipitation reaction at room temperature [39]
Summary
Several types of atomic clusters with various amounts of Mg and Si are formed [1, 2]. Cheng et al [30,31,32,33] studied the work hardening of several tempers of AAxxx and AA7xxx alloys based on tensile tests, spanning from the supersaturated solid solution to overaged conditions. The initial work hardening rate was seen to decrease with ageing up to the peak-aged condition Upon overageing it increased again as the particles grew in size and became non- shearable. In order to fully understand the work hardening and deformation mechanisms, it is necessary to study the behaviour up to larger strains and methods other than tensile tests should be used. In order to study the evolution in deformation structure with strain, three tempers of the AA6082 alloy were examined: W60: Solution heat-treated at 540°C for 15 minutes, quenched and stored at room temperature for one hour before deformation. The angle between a and c (105°) is seen
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