Effects of Precipitation State on Serrated Flow in Al-Mg(-Zn) Alloys

Abstract

The effects of the aging conditions on the serrated ow in Al-Mg(-Zn) alloys were investigated, focusing on the precipitation states. Al6%Mg and Al-6%Mg-3%Zn alloys were naturally and arti cially aged after solution treated and quenched. The serrated ow was examined by tensile test. As for the Al-6%Mg-3%Zn alloy, the naturally aged specimens show the increase in the critical strain for serrated ow. The Zn-Mg clusters are formed during natural aging. Furthermore, the increase in the number density and the size of these clusters corresponds to the increases in the critical strain, which reveals that the formation of these coherent clusters is one of the dominant factors for delaying the onset of serrated ow. On the other hand, as for the arti cially aged specimens in the under-aged conditions, the transformation of the clusters to the incoherent meta-stable precipitates brings about the decrease in the critical strain. Furthermore, the increase in the volume fraction of these precipitates in the over-aged conditions reduce the stress amplitude of serrated ow, which are brought about by the decrease in the solute Mg content.

Precipitation behavior of Al-Si-Cu-Mg(-Fe) alloys by a deformation-semisolid extrusion process

“…The precipitate microstructure of Al-Cu-Mg-Si alloys is affected by a combination of dislocations and natural aging [41]. The dislocations formed from the D-SSE aid in the formation of Q' phase [36,42]. The high density of disordered and fine precipitates with good thermal stability observed in the present work is probably due to Cu encapsulation of the Mg-Si phases, preventing their growth [43].…”

“…A HAADF-STEM image is displayed in (d), filtered by selecting the corresponding cluster spots in the FFT of the image, and using Gaussian blur in DigitalMicrograph on the IFFT image to improve the visibility of the atomic clusters. The Curich clusters are extremely small and with much less structure than, for example, the clusters in the Al-Mg-Zn system [36].…”

Effect of Compositional and Processing Variations in New 5182-Type AlMgMn Alloys on Mechanical Properties and Deformation Surface Quality

“…For 5xxx-series alloys, it is known that the serrated flow is reduced when Zn is added. This effect is caused by the formation of Zn‒Mg clusters (T-phase (Mg 32 (Al, Zn) 49 ) precursor) during NA, which causes depletion of solute Mg in the matrix [68,69]. A similar effect can be assumed for Cu‒Mg cluster formation in Cu-modified alloys [55].…”