Grain Boundary Character Distributions and Discontinuous Precipitation in a Brass H80 Alloy with Cold Rolling and Annealing

A recrystallized brass H80 alloy was cold rolled with small strain of 6% (thickness reduction) and then annealed at low temperature (633 K) for 4-96 h. The grain boundary character distributions (GBCD) and discontinuous precipitation in the processed samples were studied by means of electron back scatter diffraction (EBSD) and scanning electronic microscope (SEM). The results show that the fraction of so-called Sigma 3(n) (n=1, 2, 3) special boundaries (f(SBs)) was increased at first and then dropped with increments of annealing time after rolling. A peak value (76%) of SBs fraction was obtained when the annealing time reached 48 h, and meanwhile, the averaged size of the cluster of some special grain (SGs) interfaced by Sigma 3(n) (n=1, 2, 3) SBs exceeded 100 gm and the connectivity of random boundary network was essentially interrupted by SBs. Discontinuous precipitation occurred when the annealing time reached 72 h. Since the precipitates were interfaced by a smaller averaged size (about 20 mu m) of SGs clusters.