EFFECTS OF ALLOY MODIFICATION AND THERMOMECHANICAL PROCESSING ON RECRYSTALLIZATION OF AL-MG-MN ALLOYS

The 5083 Al alloy (A1-4.75Mg-0.8Mn) holds potential for superplastic f orming (SPF), but slow rates of forming limit its use for many applica tions. Higher strain rates are believed possible through the developme nt of finer grained microstructures or stabilized subgrain structures. Grain sizes after recrystallization and recrystallization characteris tics are known to be dependent on the amount and distribution of secon d-phase particles in the matrix. In this study, the concentration and sizes of such particles were varied by additions of particle-forming e lements of Mn and Zr and by modifications of the rolling and aging sch edules (thermomechanical processing (TMP)). The investigation involved studying recrystallization kinetics at different temperatures and cor relating the grain sizes with particle sizes and volume fractions. The addition of Mn and Zr, for the composition ranges and TMP methods stu died, resulted in a substantial reduction of the recrystallization kin etics, but complete suppression of static recrystallization (or subgra in stabilization) was not observed. However, statically recrystallized grain sizes as small as 6 mu m were achieved.