Microstructural Evolution and Mechanical Response of Equal-Channel Angular Extrusion-Processed Al-40Zn-2Cu Alloy

Abstract

Microstructural evolution, tensile properties, and impact toughness of an aluminum-zinccopper (Al-40Zn-2Cu) alloy subjected to repetitive equal-channel angular extrusion (ECAE) up to four passes following either route A or route B C were investigated. The experimental results reveal that the ECAE eliminated as-cast dendritic microstructure along with casting defects such as microporosities almost completely. The ECAE-processed samples consisted of mostly elongated microconstituents via route A and equiaxed microconstituents via route B C . The high stresses imposed in ECAE lead to the fragmentation of the copper-rich h phase into smaller particles with significant fragmentation occurring in the first pass and additional breaking in the subsequent passes in both routes. The ECAE processing simultaneously increased both the strength and ductility of the alloy as compared to the as-cast state, regardless of the processing route and number of passes. The deformation behavior of as-cast Al-40Zn-2Cu alloy has changed from brittle to ductile mode after ECAE due to the microstructural refinement, deformation-induced homogenization, and reduction of porosities. The limited impact toughness of as-cast alloy was significantly improved by multipass ECAE, especially in route A.

Formability of Ultrafine-Grained Interstitial-Free Steels

“…[2] Ultrafine-grained (UFG) materials produced by severe plastic deformation (SPD) with grain sizes in the range of 100 to 1000 nm have received considerable attention due to their higher strength combined with an adequate ductility compared to their coarse-grained (CG) counterparts. [3][4][5][6][7][8][9][10][11][12][13] Among the available SPD methods, equalchannel angular extrusion (ECAE) is considered to be the most capable one to control the resulting microstructural features of the UFG materials like grain size, grain morphology, and grain boundary character. [14,15] UFG materials have been identified as promising candidates for micro-forming processes due to their submicron-sized structures.…”

Effect of equal channel angular pressing on microstructural and mechanical properties of as cast Al–20 wt-Zn alloy

“…This behaviour occurring after further deformation can be attributed to the deformation induced homogenisation of the phases. This homogenisation effect in Zn-Al alloys during warm equal channel angular extrusion processing was the main topic of the study performed by Purcek et al 26 In that study, the reason of worksoftening was discussed, and they found that individual phase compositions in two phase as cast alloys approached to each other and the volume fraction of the hard phase dropped with the number of equal channel angular extrusion passes in relatively high processing temperature (T H 50?41). They concluded that further deformation had no considerable effect on strengthening of the as cast alloy.…”

“…The mechanical properties of Al-Zn alloys are strongly influenced by dendritic structure as indicated in previous studies. 26,31,32 Shrinkage microporosities formed as a result of dendritic solidification limit the strength and ductility of the alloy due to the increased cracking tendency. 32 McKenzie et al 33 studied the porosity reduction during ECAP and found that the number of pores in the as cast structure significantly decreased with ECAP.…”

“…[26][27][28] As a result of these efforts, a considerable improvement in strength, ductility and impact toughness was achieved, and it was also found that the mechanical properties of the alloys showed sensitivity to the ECAP parameters, mainly the number of passes and processing routes. [26][27][28][29] However, the effect of ECAP processing on the microstructure and mechanical properties of high aluminium containing (Al content, .60%) alloys and the fatigue behaviour of any Al-Zn alloy produced by ECAP have not been investigated yet. The improved mechanical properties and high fatigue performance, necessary for designing and manufacturing of the components or machine parts such as bearings, shafts, pulleys and gears, are very important to enhance the usage of these alloys having many advantages compared with other non-ferrous metals.…”

Texture evolution of an Al-8Zn alloy during ECAP and post-ECAP isothermal annealing

“…For commercial purity Al deformed after multi-pass ECAP, it has been found that compared to route Bc, the texture strength developed in route C is higher up to four passes [20]. So far, ECAP has been applied to some Al-Zn alloys with eutectic [39], eutectoid [40] and monotectoid compositions [41], whereas there appears to be a lack of investigations on the texture evolution of binary Al-Zn alloys containing less than 10 wt.% Zn during large number of ECAP passes. In addition to ECAP route and number of passes, annealing is expected to be another factor that can influence the formation of microstructures and textures.…”