Question

Explain all domestic and global consequence of deformation in your language​

Answer 1

Answer:

3.5 Grain refinement by HE

Specific deformation conditions during multipass HE ensures a very high efficiency of grain refinement. The microstructure developed by HE in various metals (such as Al, Cu, Ti) can be diversified, from equiaxed grains having low dislocation density in Al (Fig. 3.3A) and dislocation cells in Cu (Fig. 3.3B), to nanometric grains with high dislocation density in Ti [22,30–33]. The grain size of all mentioned metals hydrostatically extruded with the strain of ɛ = 3.82 was lower than 1 μm, but nanostructure was achieved in titanium only.

The analysis of the microstructural evolution during the HE process revealed that the first stage of extrusion leads to a meaningful increase of dislocation density in the material. Accumulated dislocations form lamellar structures (elongated bands) separated by boundaries, which successively evolve during the deformation, to the formation of high angle grain boundaries (HAGBs). Shape “twins” can be formed at the beginning stages of plastic deformation