Microstructure and Texture Development in Alpha-Brass Using Repetitive Thermomechanical Processing

Repetitive thermomechanical processing (TMP) has been applied to evaluate the effect of compression strain and temperature on microstructure and texture development in an alpha-brass alloy. Two TMP schemes were employed using four cycles of low-strain compression (ε = 0.15) and annealing, and two cycles of medium-strain compression (ε = 0.3) and annealing. Compression tests were conducted at 25, 250, and −100 °C, while annealing was made at 670 °C for 10 min. Examination by electron backscattered diffraction (EBSD) indicated that the low-strain scheme was capable to increase the fraction of Σ3ⁿ boundaries (n = 1, 2, and 3) with increasing cycles, producing maximum fraction of 68%. For medium-strain scheme, a drop in the fraction of Σ3ⁿ boundaries occurred in cycle 2. Reducing compression temperature lowered the fraction of Σ3ⁿ boundaries for low-strain scheme, while it enhanced the formation of Σ3ⁿ boundaries for medium-strain scheme. Annealing textures showed that 〈101〉 compression fiber was strongly retained for samples processed by small-strain scheme, while weakening of 〈101〉 fiber accompanied by the formation of 〈111〉 recrystallization fiber occurred for the medium-strain scheme. The results indicate that the increase in strain energy stored during compression, via increasing strain and/or decreasing deformation temperature, is responsible to favor recrystallization twinning over strain-induced grain boundary migration (SIBM). Both mechanisms are important for the formation of Σ3ⁿ boundaries. Yet, SIBM is thought to strongly promote regeneration of Σ3ⁿ boundaries at higher TMP cycles. This is consistent with the development of microstructure and texture using small-strain scheme.