THE EFFECT OF PARTICLES ON TEXTURE EVOLUTION IN COMMERCIAL AIMn

Two commercial Aluminium alloys with high Mn content were investigated in three different precipitation states. The rolling textures possess a portion of random orientations that is proportional to the volume fraction of larger particles. It is therefore identified with their deformation zones having about double the diameter of the particles. The recrystallization textures are weak for high annealing temperatures and show the more retainedrolling texture the more the temperature is lowered. This is interpreted as amatterofnucleation site. Butalso growth mechanisms influence the texture evolution. Minor texture components are characteristic for the different conditions. EXPERIMENTAL Two commercial AIMn alloys containing 1.1 wt.-% Mn (direct cast: DC) and 2.1 wt.-% Mn (strip cast: SC) were investigated. Through suitable heat treatments both obtained three different precipitation states varying from highly supersaturated (DC-1, SC-1) to fully precipitated condition (DC-3, SC-3). The intermediate state (DC-2, SC-2) was achieved by 30% cold rolling ofthe highly supersaturated material followedby aprecipitation annealing at400C. Theprecipitation state was specified by particle size distribution and conductivity measurements. All six materials were cold rolled up to 90% and the 90% reduced specimens were recrystallizeA at various temperatures in a salt bath to examine rolling and recrystallization textures with the help of ODF analysis. RESULTS & DISCUSSION Precipitation State Due to the high amount of alloying elements there are coarse particles in all materials. Table 1 shows their area fractions of the larger particles and their conductivities. While 721 722 T. RICKERT ETAL conditions 1 and 2 have very similar size distributions and consequently about the same portion of larger precipitations, they differ strongly in their amount of dissolved foreign atoms. Therefore itcanbeconcluded thatthequantity ofsmall particlesbalances theamount of supersaturated foreign atoms in condition 1, though it was not measm. However, condition 3 materials contain more and biggerparticles andabout no supersaturation. These major differences are much more pronounced in the SC-alloy than in DC alloy. Table 1 Pre-treatments and material conditions

But also growth mechanisms influence the texture evolution. Minor texture components are characteristic for the different conditions. EXPERIMENTAL Two commercial AIMn alloys containing 1.1 wt.-% Mn (direct cast: DC) and 2.1 wt.-% Mn (strip cast: SC) were investigated. Through suitable heat treatments both obtained three different precipitation states varying from highly supersaturated (DC-1, SC-1) to fully precipitated condition (DC-3, SC-3). The intermediate state (DC-2, SC-2) was achieved by 30% cold rolling ofthe highly supersaturated material followed by aprecipitation annealing at 400C. The precipitation state was specified by particle size distribution and conductivity measurements. All six materials were cold rolled up to 90% and the 90% reduced specimens were recrystallizeA at various temperatures in a salt bath to examine rolling and recrystallization textures with the help of ODF analysis.

RESULTS & DISCUSSION Precipitation State
Due to the high amount of alloying elements there are coarse particles in all materials. Table 1 shows their area fractions of the larger particles and their conductivities. While 721 conditions 1 and 2 have very similar size distributions and consequently about the same portion of larger precipitations, they differ strongly in their amount of dissolved foreign atoms. Therefore itcan be concluded thatthe quantity ofsmall particles balances the amount of supersaturated foreign atoms in condition 1, though it was not measm. However, condition 3 materials contain more and biggerparticles and about no supersaturation. These major differences are much more pronounced in the SC-alloy than in DC alloy.  In both alloys the weakest textures and highest random components are found for condition 3. As foreign atoms in supersaturation affect the texture much less than small particles, this should be compared primarily with condition I where the random portion is clearly lower at high reductions. Thus, the coarse particles create the random component rather than any other slial texture component through the development of deformation zones3. By attributing the random portion completely to these zones one can estimate their size to: R 2r (R= zone radius, r= particle radius).
Determining the random fraction of the rolling textme faces a major problem for sampling. As deformation zones are f'LrSt nucleation sites, they are changing in the very first stages of recrystallization. Before any new orientation emerges in the texture, the random componentdecreases through recovery already atroom temperature. Therefore, the detecte fractions tend to be too low. Deformation Deformation 6.6% 0.6% 0.6 Figure 2. Volume fraction of random component during rolling.
For condition 2 showing the strongest textures, the influence of small particles and the pre-rolling also have to be considered. The 30% cold rolling prior to precipitation annealing can be included into a total deformation. Still an effect of the smaller particles on inching the texture sharpness (as describe in 2 ) is found ( fig. 1).
The SC-materials, having a potential ofnearly 7% second phase, seem to develop a sort of saturation texture which doesn't change through further rolling (fig ld-f). This must be connectedwithparticularmicrostructuralprocesses,however, itwas notfurtherinvestigated.  temperature. This harmonizes excellently with a recrystallization model ofOrsund and Nes'* whorelate these texture components with different nucleation sites: (a) At high temperatures nucleation predominates in the core region of the deformation zones (random), Co) The retained rolling texture results of nucleation in the outer periphery of the zones which multiplies at lower temperatures.
Besides these two main texture components, there are minor ones (e.g.: [001 ]<210>) which are different for condition 3 than for conditions 1 and 2. But all have approximate 40<111> orientation relationships to rolling components. In fact, the texture of DC-3 after 500C anneal can be seen as a nice example for the oriented growth mechanism5. It takes place as a consequence of multiple random nucleation. At lower temperatures, these components vanish and the cube component with its RD-rotations up to Goss increase, yet being minor components stiR. They are interpreted as being formed by a Dillamore/Katoh mechanism6.
In conditions I and 2, recrystallization is strongly retarded as compared to condition 3 because ofthe supersaturated foreign atoms and small panicles, reslxtively. This results in a prevention of the cube component and a change of the minor components generally.
Remarkable is the evolution of the A-component 112}<110> which is usually found only after shear deformation although there are no hints ofthe A-component in rolling or starting textures.
The SC-matea-ials recrystallization is much more retarded than the DC's. SC-1 and SC-2 were recrystallized only at 500C forming coarse grains. But while conditions 2 and 3 develop comparable textures as the DC-materials, do SC-1 is clearly different (rigA). The cube component is supIsed to be strongly handicapped _tlFough the precipitation processes which definitely occur in the material during annealing 7. So it's appearance here may be explained by inhomogeneities in the rolled structure in connection with a very small nucleation rate of competing orientations.