Hirosuke Inagaki

Role of shear band in texture control of Al-Mg alloys

Shear bands formed in Al-Mg alloys during cold rolling are nucleated on grain boundaries. Their mechanism of formation is different from that already proposed in the case of single crystals of the same alloy. Since recrystallized grains of non-cube orientations are nucleated on these shear bands during annealing, the development of cube recrystallization texture can be strongly suppressed by enhancing shear banding during cold rolling. Control of shear band thus provides a new fundamental technological tool to improve drawability of Al alloy sheets. In a microscopic scale, deformation in grain boundary regions also plays here a very important role, as in the case of the formation of {111}uvw recrystallization textures in low carbon steel sheets.

Rolling and Recrystallization Textures in High Purity Al Cold Rolled to Very High Rolling Reductions

On the basis of Taylor-Bishop-Hill’s theory, many previous theoretical investigations have predicted that, at high rolling reductions, most of orientations should rotate along theβfiber from {110}<112> to {123}<634> and finally into the {112}<111> stable end orientations. Although some exceptions exist, experimental observations have shown, on the other hand, that the maximum on the β fiber is located still at about {123}<634> even after 97 % cold rolling. In the present paper, high purity Al containing 50 ppm Cu was cold rolled up to 99.4 % reduction in thickness and examined whether {112}<111> stable end orientation could be achieved experimentally. It was found that, with increasing rolling reduction above 98 %, {110}<112> decreased, while orientations in the range between {123}<634> and {112}<111> increased, suggesting that crystal rotation along the βfiber from {110}<112> toward {123}<634> and {112}<111> in fact took place. At higher rolling reductions, however, further rotation of this peak toward {112}<111> was extremely sluggish, and even at the highest rolling reduction, it could not arrive at {112}<111>. Such discrepancies between theoretical predictions and experimental observations should be ascribed to the development of dislocation substructures, which were formed by concurrent work hardening and dynamic recovery. Since such development of dislocation substructures are not taken into account in Taylor-Bishop-Hill’s theory, it seems that they can not correctly predict the development of rolling textures at very high rolling reductions, i. e. stable end orientations. On annealing specimens rolled above 98 % reduction in thickness, cube textures were very weak, suggesting that cube bands were almost completely rotated into other orientations during cold rolling. {325}<496>, which lay at an intermediate position between {123}<634> and {112}<111> along theβfiber, developed strongly in the recrystallization textures.

Contribution of dislocation substructures developed during cold rolling to the formation of rolling textures in Al–Mg alloys

Abstract In order to investigate the mechanism of the development of rolling textures in Al–Mg alloys, hot bands of high-purity Al, Al-3 wt. % Mg and Al-5 wt. % Mg alloys were solution-treated at 450 °C and cold-rolled by varying rolling reductions up to 97 %. Rolling textures of these specimens were investigated with the orientation distribution function analysis. Comparisons of the results of the texture analysis with those of the hardness measurement and transmission electron microscopy observations revealed that, in all specimens, the texture development occurred mainly at the later half of work hardening, i. e., at rolling reductions above 80 %, where dislocation substructures were well developed. In pure Al, in which well defined, elongated cell structures were developed, {112} and {123} components developed remarkably, whereas in the Al-5 % Mg alloys, in which only dense dislocation tangles and ill defined small cells were developed, the development of {112} and {123} components...

Rolling and recrystallization textures in Al-Mg alloys

Abstract By using the orientation distribution function analysis, rolling and recrystallization textures developed in Al–Mg alloys containing 6, 7 and 9 wt.% Mg were studied in detail. Also recrystallization behavior and precipitation of the β phase particles during annealing were investigated by using both optical and scanning electron microscopy. It turned out that cold rolling textures of these alloys were generally weak and random. The recrystallization textures of Al-6 wt.% Mg alloy annealed at 450°C were found to be strongly dependent on the heating rate to the annealing temperature. Annealing by rapid heating enhanced the formation of {103} and {100} , suppressing the development of {100} strongly. This is because {103} and {100} recrystallized grains were preferentially formed at shear bands and at peripheries of deformed cube bands, respectively. {100} recrystallized grains were consumed during grain growth by grains of these orientations. In annealing by slow heating...

Origins of Cube Recrystallization Textures in Heavily Rolled High Purity Al

In high purity (4N) Al containing 50 ppm Cu, very strong cube textures can be developed by cold rolling 98 % and annealing at 500 °C. The orientation density in this material amounted to as much as 220 times random, i. e. about 3 times stronger than that observed in standard 4N Al. It is expected that the origins of cube textures should be most unambiguously clarified by using this material. Commercial hot bands of this materials were cold rolled 98 % to the thickness of 132 μm and isothermally annealed at 230 °C. Detailed EBSP analyses were made both on the rolling plane and on the longitudinal section at each stage of annealing. It was found that in the hot band of this high purity Al, cube orientations were mostly rotated away into other orientations due to low temperature hot rolling with high rolling reductions. Therefore, regions having cube orientations were very few. They were not present in the form of so called cube bands, which had been reported in previous investigations, but in the form of isolated, rather equi-axed recrystallized grains. After 98 % cold rolling, these remaining cube regions were fragmented, and further rotated away into other orientations, so that only very few cube oriented regions were observed in the cold rolled materials. However, it was from such deformed cube oriented regions that the most potential exact cube recrystallized grains were formed. They were nucleated much earlier and grew much faster than grains of other orientations.

Texture Development in 6000 Series Al-Mg-Si Alloys for Car Body Panels

Recovery, recrystallization and the formation of recrystallization textures were investigated in three representative Al-Mg-Si alloys used for car body panels. Commercial hot bands of AA6016, AA6111 and AA6061 Al-Mg-Si alloys finished at low temperatures were cold rolled to a rolling reduction of 95 % in thickness and isothermally annealed at temperatures between 250 and 500 °C. In these alloys, precipitation was completed for the most part during low temperature hot rolling, and the sizes and the amount of fine precipitates formed during this low temperature hot rolling strongly affected recrystallization and the development of recrystallization textures. As a result, in the specimens annealed at 300 °C, quite different recrystallization behavior and recrystallization textures were observed. In the AA6061 alloy, in which, among three alloys, the maximum amount of Mg2Si should be precipitated, recrystallization was significantly suppressed. This resulted in the formation of strong {110} <111> and {100} <013> recrystallization textures. Also in the AA6111 alloy, in which precipitation of a medium amount of Mg2Si was expected, recrystallization was retarded to the same extent. In this alloy, however, recrystallization textures consisted of very strong {100} <001> and rather strong {110} <111> main orientations. In theAA6016 alloy, in which the minimum amount of Mg2Si and a large amount of Si particles should be precipitated, recrystallization occurred very rapidly, forming very weak recrystallization textures. In all alloys, annealing at higher temperatures resulted in the formation of weak textures, since fine precipitates were dissolved during annealing. Thus, the solution treatment, which is a necessary step to induce bake hardening in these alloys, randomizes their recrystallization textures.