The present
study investigated the mechanical properties and microstructure of ultrafine
grained (UFG) brass processed by four passes of equal channel angular pressing
(ECAP) and annealed at elevated temperatures. The mechanical properties of all
samples were assessed using tensile and micro-hardness tests. Microstructure
analysis was performed using optical microscopy (OM) and scanning electron
microscopy (SEM). Ultimate tensile strengths (UTS) and yield strengths (YS) of
878 and 804 MPa, respectively, ductility of 15%, and hardness of 248 HV were
obtained for samples processed by four passes of ECAP with equivalent true
strain of 4.20. Annealing at 300°C caused UTS and YS to decrease significantly,
to 510 and 408 MPa, respectively, ductility to increase to 28%, and hardness to
decrease to 165 HV. Fractography analysis of un-annealed samples after four
ECAP passes showed small brittle fractures with shallow dimpling. Ductile
failures were found on annealed samples. After four ECAP passes, the
microstructure of un-annealed samples was UFG and dominated by lamellar grain
with shear band. In contrast, after annealing, the microstructure changed due
to recrystallization, showing nucleation and grain growth.
