• Olejnik, Lech
• Lipińska, Marta
• Chromiński, Witold
• Lewandowska, Małgorzata
• Rosochowski, Andrzej
• Goliński, Jacek

Abstract

In this study, an Al-Mg-Si alloy was processed using via incremental equal channel angularpressing (I-ECAP) in order to obtain homogenous, ultrafine-grained plates with low anisotropyof the mechanical properties. This was the first attempt to process an Al-Mg-Si alloy using thistechnique. Samples in the form of 3 mm-thick square plates were subjected to I-ECAP with the90 deg rotation around the axis normal to the surface of the plate between passes. Samples wereinvestigated first in their initial state, then after a single pass of I-ECAP, and finally after foursuch passes. Analyses of the microstructure and mechanical properties demonstrated that theI-ECAP method can be successfully applied in Al-Mg-Si alloys. The average grain size decreasedfrom 15 to 19 lm in the initial state to below 1 lm after four I-ECAP passes. The fraction ofhigh-angle grain boundaries in the sample subjected to four I-ECAP passes lay within 53 to57 pct depending on the examined plane. The mechanism of grain refinement in Al-Mg-Si alloywas found to be distinctly different from that in pure aluminum with the grain rotation beingmore prominent than the grain subdivision, which was attributed to lower stacking fault energyand the reduced mobility of dislocations in the alloy. The ultimate tensile strength increasedmore than twice, whereas the yield strength was more than threefold. Additionally, the platesprocessed by I-ECAP exhibited low anisotropy of mechanical properties (in plane and across thethickness) in comparison to other SPD processing methods, which makes them attractive forfurther processing and applications.

Topics

• surface
• grain
• grain size
• mobility
• aluminium
• strength
• positron annihilation lifetime spectroscopy
• Photoacoustic spectroscopy
• dislocation
• yield strength
• tensile strength
• stacking fault
• pure aluminum