Grain Refinement in As-Cast 7475 Aluminum Alloy under Hot Equal-Channel Angular Pressing

Abstract

Microstructural evolution taking place during equal channel angular pressing (ECAP) was studied in an as-cast 0.16%Zr modified 7475 aluminum alloy at a temperature of 673 K. The structural changes are characterized by development of deformation bands due to large strain inhomogeneity occurring through the ECAP die. Repeated deformation leads to an increasing of number and misorientation angle of the boundaries of deformation bands, finally followed by formation of new fine grains at high strains. The misorientation angle distribution for newly developed boundaries shows a single peak type at relatively low misorientations in low strain and changes to a bimodal distribution with two peaks at low and high misorientations in moderate strain. Pressing to a strain of 12 leads to a full development of new grains surrounded by medium to high angle boundaries with an average size of about 1.7 mm. It is concluded that grain refinement occurs by a deformation-induced continuous reaction, that is essentially similar to continuous dynamic recrystallization.

Partial Grain Refinement in Al-3%Cu Alloy during ECAP at Elevated Temperatures

“…There are several reports to date dealt with the investigation of the fine-grained structure evolution in Al alloys at different temperatures during SPD. [2][3][4]6,8,9,[11][12][13][14]16,[18][19][20][21][22][24][25][26] Under severe plastic deformation conditions, fragmentation of original grains takes place at medium strains followed by in-situ formation of fine crystallites at high strains, which is sometimes called as continuous dynamic recrystallization (CDRX). 9,16,[18][19][20]22,24,25) Such structural changes in Al alloys during SPD are mostly investigated at ambient temperature and only few studies address high-temperature SPD and UFG formation at elevated temperatures.…”

“…[2][3][4]6,8,9,[11][12][13][14]16,[18][19][20][21][22][24][25][26] Under severe plastic deformation conditions, fragmentation of original grains takes place at medium strains followed by in-situ formation of fine crystallites at high strains, which is sometimes called as continuous dynamic recrystallization (CDRX). 9,16,[18][19][20]22,24,25) Such structural changes in Al alloys during SPD are mostly investigated at ambient temperature and only few studies address high-temperature SPD and UFG formation at elevated temperatures. 6,[8][9][10]12,13,16,[18][19][20][24][25][26] The present authors have investigated the microstructural evolution in Al alloys during hot SPD in the recent works.…”

“…1) Several SPD techniques such as equal channel angular pressing (ECAP), [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] torsion under high pressure 1,3,21) and multi-directional forging (MDF) [22][23][24][25][26][27][28] are now available for attaining of the UFG structures in numerous metals and alloys. There are several reports to date dealt with the investigation of the fine-grained structure evolution in Al alloys at different temperatures during SPD.…”

Effect of Heat Treatment on Impact Toughness of Aluminum Silicon Eutectic Alloy Processed by Rotary-Die Equal-Channel Angular Pressing

“…[1][2][3][4][5][6][7][8] After ECAP processing, the alloy usually has a fine-grained microstructure ranging from several hundred nanometers to several microns. 9,10) Therefore, ECAP is an attractive process for improving the mechanical properties of metallic materials.…”

Microstructural Characteristics of Ultrafine-Grained Nickel

“…However, both of these parameters play a significant role in determining the bulk properties of the materials [27,28]. Some information has become available recently on the grain boundary misorientation distributions after ECAP of pure Al and Al alloys [29][30][31][32][33][34][35][36][37][38][39], ECAP of pure Cu [38,40,41], ECAP and HPT of pure nickel [5,42] and ECAP of pure Zr [43]. Although the results on pure Ni are fairly limited [42], the experimental data suggest that HPT produces a microstructure with a higher fraction of high-angle grain boundaries than ECAP.…”