SOME OBSERVATIONS ON DEFORMATION BANDING AND CORRELATED MICROSTRUCTURES OF 2 ALUMINUM-ALLOYS COMPRESSED AT DIFFERENT TEMPERATURES AND STRAIN RATES

In compressed samples of high-purity aluminum alloys, without (Al-0.5 wt% Cu) and with hard precipitates (Al-0.5 wt% Cu-1.0 wt% Si), a varie ty of deformation band patterns has been observed, including occasiona l exquisite detailed structuring. According to the present preliminary results, the banding does not significantly depend on strain rates be tween 0.05 and 100%/s, nor on temperature from ambient to cryogenic (- 193 degrees C). However, it is greatly decreased by the presence of pr ecipitates in the Al-Cu-Si alloy and was barely if at all visible at a nd above 200 degrees C. The banding is due to changing selections of o perating slip systems, falling short of the five required in the Taylo r model of homologous deformation in polycrystals. The occasional exqu isite detail in the banding pattern is accepted as virtual proof of th e low-energy dislocation structure (LEDS) hypothesis, the basic tenet from which the LEDS theory of crystal plasticity follows without furth er assumptions. In agreement with this interpretation, also the underl ying dislocation cell structure, which did not reveal any evident corr elation with the deformation banding, as well as the observed workhard ening features as dependent on strain rate and temperature are in acco rd with the LEDS theory. Acta Metallurgica Inc. Published by Elsevier Science Ltd.