Diffusive transformation at high strain rate: On instantaneous dissolution of precipitates in aluminum alloy during adiabatic shear deformation

The suitability of aluminum alloys in a vast majority of engineering applications forms the basis for the need to understand the mechanisms responsible for their deformation and failure under various loading conditions. The material investigated in this study is AA 2219-T8 aluminum alloy. Supplied by the NASA Research Center, with high strength to weight ratio and corrosive resistance. Containing a unique mixture of aluminum, copper, and other trace elements, this alloy has potential applications in multiple fields including aerospace, defense, and commercial industries. In this paper, the dynamic high strain rate impact deformation of the AA2219-T8 aluminum alloy was performed using the split Hopkinson pressure bars. The evolution of localized strain in the aluminum samples during the deformation process obtained using high speed digital cameras is reported. Microstructural analysis of deformed aluminum samples was also performed using optical microscopes in order to determine the influence of impact strain rate on localized strain along narrow adiabatic shear bands in the AA2219-T8 aluminum alloys. Results obtained indicate that peak flow stress in the deformed aluminum sample depends on the strain rate at which the deformation test was performed. The non-uniformity of the strain obtained using the digital image correlation as deformation time progresses shows two distinct areas of non-uniform strains that may be indicating potential sites for the formation of adiabatic shear bands in the tested samples.

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High Strain Rate Superplasticity in a Zr and Sc Modified 7075 Aluminum Alloy Produced by ECAP

Materials Science Forum ◽

10.4028/www.scientific.net/msf.584-586.164 ◽

2008 ◽

Vol 584-586 ◽

pp. 164-169 ◽

Cited By ~ 6

Author(s):

Krystof Turba ◽

Premysl Malek ◽

Edgar F. Rauch ◽

Miroslav Cieslar

Keyword(s):

Aluminum Alloy ◽

High Strain Rate ◽

Strain Rate ◽

High Strain ◽

Rate Sensitivity ◽

7075 Aluminum Alloy ◽

Fine Grained ◽

Angular Pressing ◽

Average Grain Size ◽

Elongation To Failure

Equal-channel angular pressing (ECAP) at 443 K was used to introduce an ultra-fine grained (UFG) microstructure to a Zr and Sc modified 7075 aluminum alloy. Using the methods of TEM and EBSD, an average grain size of 0.6 1m was recorded after the pressing. The UFG microstructure remained very stable up to the temperature of 723 K, where the material exhibited high strain rate superplasticity (HSRSP) with elongations to failure of 610 % and 410 % at initial strain rates of 6.4 x 10-2 s-1 and 1 x 10-1 s-1, respectively. A strain rate sensitivity parameter m in the vicinity of 0.45 was observed at temperatures as high as 773 K. At this temperature, the material still reached an elongation to failure of 430 % at 2 x 10-2 s-1. These results confirm the stabilizing effect of the Zr and Sc additions on the UFG microstructure in a 7XXX series aluminum alloy produced by severe plastic deformation.

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