Investigation on Microstructure Evolution of Hot Deformed Free-Cutting Cu-Zn-Se-Bi-Sn Alloy

The microstructure evolution of hot deformed Cu-Zn-Se-Bi-Sn alloy was investigated by Hitachi-800 transmission electron microscopy (TEM). The result shows that there are three different dislocation configurations such as dislocation network, dislocation wall and dislocation cell in hot deformed Cu-Zn-Se-Bi-Sn alloy. The dislocation network was firstly formed in some certain grains of Cu-Zn-Se-Bi-Sn alloy when the deformation strain amounted to 2%. Then dislocations initially arranged regularly beside original grain boundaries and the arranged dislocation walls were formed in some area and sub-grains merging emerged when the deformation strain amounted to 20%. Eventually, obvious dynamic recrystallization nucleation by sub-grain merging emerged in Cu-Zn-Se-Bi-Sn alloy when the strain attached 80%.

On the swelling resistance of ferritic steel

Transmission electron microscopy has been used to study the microstructural features associated with void swelling resistance in FV448 martensitic stainless steel after fast reactor irradiation to damage levels of 30 dpa at temperatures in the range 380-460 °C. A characteristic feature of the microstructures is the presence of domains in which the high pre-irradiation network dislocation density is eliminated, and replaced by a homogeneous population of interstitial dislocation loops with a ⟨100⟩ Burgers vectors. These domains grow but remain interspersed within a martensitic-type matrix that still retains high network dislocation densities. It is suggested that the observed evolution of the damage structure and the associated swelling resistance in such b.c.c. materials is due to the relative rates of nucleation and growth of the two interstitial dislocation loop types, with 1/2 a ⟨111⟩ and a ⟨100⟩ Burgers vectors.