Published by Maney Publishing (c) IOM Communications Ltd Effect of pretreatment and texture on recovery and recrystallisation in AI-4-5Mg-O-7Mn alloy O. Engler, I. Heckelmann, T. Rickert, J. Hirsch, and K. Lucke The developm.ent of recovery a.nd recrystallisation in cold rolled Al-4·5Mg-0·7 Mn (designated AA 5083) was analysed metall0!5.r~~hzcally, by measurz~g har.dness and e~ectrical conductivity, and by means of texture analysis. The precipitation state and the znztzal te~tu~e were varzed uszng a?proprz.ate pretreatments before cold rolling in order to study the influence of these parameters on kznetzcs and texture evolutlOn durzng deformation, recovery, and recrystallisation. Finally, the results obtained were compared with those obtainedfor conventionally produced material. MST/1960 © 1~94 The Institute of Materials. Manuscript received 30 July 1993; in final form 6 October 1993. At the time the work was c~rrzed out the authors were at the Institut fur Metallkunde und Metallphysik, R WTH Aachen, Germany. Dr Rickert is now wzth Allegheny Ludlum Steel, Brackenridge, PA, USA and Dr Hirsch is now with VAWaluminium AG, Research and Development, Bonn, Germany. Introduction the sheet is known to determine the plastic anisotropy of the material, thereby influencing the deep drawability, e.g. Refs. 5 and 6. Table 1 Exact composition of investigated material (AA 5083 alloy), wt-% The last decade saw considerable growth in the use of aluminium alloys for beverage packaging. Currently, the bodies of beverage cans are made from 3000 series AI-Mn alloys (e.g. 3004) whereas the can stock end is made from 5000 series AI-Mg-Mn alloys. Such cans are produced from rolled sheets oy deep drawing. In order to protect the material from the contents which may be corrosive, a coating is applied. The 5000 series alloys experience a certain drop in mechanical strength during annealing at temperatures above 200°C which may occur during the coating process. Therefore, it is interesting to study the recovery and recrystallisation behaviour responsible for the decrease in strength of such material. It is generally known that large particles (> 1 /-lm) may enhance recrystallisation by particle stimulated nucleation (PSN), e.g. Refs. 1-3. On the other hand, small precipitates as well as solute atoms may retard recrystallisation since they affect the mobility of both dislocations and grain boundaries (which determine the recovery and recrystallis- ation respectively). In commercial aluminium alloys which usually contain large and small precipitates as well as solutes, these effects can overlap. Therefore, it should be possible to control the recrystallisation behaviour and consequently the softening of the material by an appropriate thermomechanical treatment. The present paper focuses on the recovery and the recrystallisation behaviour of the AI-4·5Mg-0·7Mn alloy (AA 5083), known already from earlier investigations. 4 In order to vary the material condition with respect to precipitation state and initial texture, various pretreatments were performed using different forging and annealing treatments before cold rolling. The evolution of recovery and recrystallisation was studied for various sample sets after isothermal annealing for various times until recrystal- lisation had been completed. The investigation included metallography, Vickers hardness, and electrical conductivity measurements; and texture analysis based on the three dimensional orientation distribution functions (ODF). The latter is of particular interest since the final texture of Mg 4·6 Mn 0·7 Fe Si 0·15 Ti 0·02 Cu <0·05 Cr <0·02 Zn <0·02 Experimental methods Electrical conductivity was determined using the eddy current device Sigmatest (Forster, Germany). This equip- ment allows the rapid measurement of the electrical conductivity in the regime 5-62 m 0-1 mm -2, independent of temperature. The accuracy for these measurements is given to 1 % of the maximum conductivity (i.e. ±0·6 m a-I mm- 2 ). For the present AI-Mg alloy exhibit- ing a conductivity of 15-20 m 0-1 mm - 2 (see below) the accuracy is about ± 50/0. At sample thicknesses below 1 mm no absolute values can be determined. However, for a given thickness, relative data can be obtained which also allow conclusions on precipitation reactions of the material. Pole figure data were acquired by means of an aut~mated X-ray texture goniometer in the back reflection mode 7 and were subsequently carefully corrected with respect to the defocusing error and the background intensity. The ODFs f(g) were calculated from four incomplete pole figures ({Ill}, {002}, {022}, and {113}; 5° ~ a~ 85°) using the series expansion method 8 (lmax = 22). The orientation g is given in form of the Euler angles qJl, <1>, and qJ2, which transform the crystallographic orientation into the sample coordinate system given by the rolling, transverse, and normal directions RD, TD, and ND respectively. All ODFs were ghost corrected with the help of Gauss type scattering functions,9 and quantitatively described.in terms of volume fractions of a number of texture components. Characterisation of alloy The investigated material was cut from a direct chill (DC) cast bar of the commercial alloy AI-4'5Mg-0'7Mn (AA 5083). The exact composition (wt_%) is given in Table 1. Aluminium alloys of the 5000 series, such as that used in the present study, are so called non-heat treatable alloys. This means that they reach their final mechanical strength by strain hardening and solution hardening without a special heat treatment. Nevertheless, in most AI-Mg alloys precipitation reactions occur which, however, do not significantly influence the strength of the materials (e.g. see Ref. 10). According to the binary phase diagram a maximum Materials Science and Technology September 1994 Vol. 10 771