Tiansheng Wang

Dislocation-Twin Boundary Interactions Induced Nanocrystalline via SPD Processing in Bulk Metals

This report investigated dislocation–twin boundary (TB) interactions that cause the TB to disappear and turn into a high-angle grain boundary (GB). The evolution of the microstructural characteristics of Hadfield steel was shown as a function of severe plastic deformation processing time. Sessile Frank partial dislocations and/or sessile unit dislocations were formed on the TB through possible dislocation reactions. These reactions induced atomic steps on the TB and led to the accumulation of gliding dislocations at the TB, which resulted in the transition from coherent TB to incoherent GB. The factors that affect these interactions were described, and a physical model was established to explain in detail the feasible dislocation reactions at the TB.

Formation of nanocrystalline during flash welding of 0Cr16Ni22Mo2Ti steel

A nanocrystalline layer was fabricated in bond area of 0Cr16Ni22Mo2Ti austenite steel using flash welding. The mean grain size near bond line is about 20 nm, and the farther the distance from bond line, the larger the size of the nanocrystalline. The thickness of the nanocrystalline layer is about 50 μm. The formation mechanism of the nanocrystalline may be that the metal in semisolid state is deformed severely and its solid grains are fragmented.