Optimization of Mechanical Characteristics of Cu-35.8%Zn Brass by Rotary Swaging and Subsequent Annealing.

The effect of rotary swaging (RS) at room temperature and subsequent annealing at 350 °C on the microstructure, mechanical properties, and fatigue strength of Cu-35.8%Zn two-phase brass was studied. A structure with grains of α and β' phases elongated along the deformation direction was formed after RS. It was also shown that subgrains of 200-300 nm in size, shear bands 100-200 nm wide, and deformation twins 10-30 nm wide were formed inside the α-phase grains. RS caused the increase in the yield stress (YS) from 93 ± 4 to 717 ± 6 MPa and the ultimate tensile strength (UTS) from 332 ± 2 to 744 ± 19 MPa with a decrease in ductility (El) from 71.0 ± 2.0 to 10.3 ± 1.7%. The fatigue limit also increased from 240 to 415 MPa after RS. Subsequent annealing at 350 °C induced recrystallization of the α-phase with the formation of equiaxed grains 2.2-3.6 µm in size, which resulted in a decrease in UTS to 462-466 MPa and an increase in ductility to 44-45%. Extending the annealing time to 4 h did not affect the strength and ductility values of the alloy.