I cannot seem to find any data on the recrystallisation temperature of EN AW-6060 or similar alloys. Can anybody please supply me with experimental data?
That is only true for pure metals and it is in temperature in Kelvin, not in Celsius. Therefore, for pure aluminum, Trec is at about 80..100°C. I am looking for Trec for a 6060 (AlMgSi0.5) alloy.
The rule of thumb for the recrystallization temperature Trecryst is that Trecryst equals about 0.4 - 0.5 Tm. with Tm = the melting temperature in Kelvin. AA 6060 is a typical extrusion alloy. The recrystallization temperature of alloys will be increased as compared to pure aluminium due to pinning of the grain boundaries resulting from the presence of solute atoms and/or intermediate phase (the critical deformation for recrystallization is for most metals 2 % in the range of the temperatures indicated by the rule of thumb, so my first guess would be that the possible effect linked to variations thereof can be neglected in a first approach). The actual value of Trecryst will also depend on the starting value of the grain size, albeit a minor effect.The foregoing denotes that there is no simple formula to predict Trecryst in terms of alloy composition.
From the extrusion point of view it may seem desirable to discriminate between the recrystallization temperature and the extrusion temperature. Extrusion is generally performed above the recrystallization temperature. To ensure full recrystallization during extrusion it seems appropriate to apply a safe temperature gap above Trecryst. Besides, the energy needed to perform the hot extrusion decreases with increasing temperature, although melting of the alloy should be prevented of course.
It depends on the thermo-mechanical treatment. if it is rolled to 90% or 75% of reduction. I have performed in situ EBSD on 7xxx series which was reduced to 75% the recrystallization initiated at temperatures around 250 to 275 degrees because of surface energy but for bulk, the recrystallization is expected to happen at 400 or above.
The thumb rule is 0.4 to 0.5Tm but it will change with the amount of prior cold deformation. In case the prior cold deformation is high the recrystallisation can be lowered significantly. Ex. in case of ECAP it can be as low as 0.1Tm. So it is very important to know the prior thermomechanical processing history of the material so as to estimate the T rex.
A recrystallization diagram is a three-dimensional representation of the relations between prior deformation, temperature and resulting grain size. The alloy composition is given for such a diagram. Indeed, the prior cold deformation determines to a large extent the actual occurring value of the recrystallization temperature, see the example given by Anil Kumar V (which alloy processed by ECAP?) It is noted that 0.1 Tm for aluminium alloys corresponds to about minus 180 centigrades). In view of processing the desired grain size is very important. Hence, the recrystallization temperature in relation to the extrusion temperature should be chosen very carefully. Given the above discussion, there is no simple formula to predict the recrystallization temperature in terms of alloy composition.
It is universally known about the thumb rule of 0.4-0.5 Tm is normally recrystallization temperature for most of the alloys. But it is also true it depends on degree of deformation especially the last deformation, which results in availability of dislocation i.e. dislocation density. As rightly told by Anil Kumar, it is linked with prior deformation and its dislocation density. Accordingly temperature for recrystallization comes down. Required temperature can be selected accordingly.