Influence of fire times on the microstructure and mechanical properties of forgings with complex shape

Influence of forging fire times on the microstructure and mechanical properties of 7A09 aluminum alloy forgings with complex shapes was investigated by means of tensile test, optical microscope (OM) observation, transmission electron microscope (TEM) observation and scanning electronic microscope (SEM) observation in order to obtain optimal fire times of forging. The results show that the grains and coring segregations are elongated in the deformation direction and present zonal distribution (zonal structures are formed) because the deformation degree is too large under the one fire time forging, which causes the mechanical properties, especially the lateral performances to decrease greatly. Under the three fire time forging, the deformation drops into or near the critical deformation zone because the deformation degree of each fire times is too small, which also causes the mechanical properties to decrease. While each property of the forgings is very high under the two fire time forging. Therefore, the two fire time forging should be taken when isothermal die forging is carried out.