Grain boundary characteristic distribution during hot extrusion for TA15 alloy

The variation of grain boundaries character distributions of TA15 alloy during hot extrusion were investigated. The specimens were hot extruded at 850, 925 and 960°C, at 0.3mm/s and 0.1mm/s with strain of 80%, 60% and 40%, respectively. The results show that special grain boundary ratio decreases in deformed specimen than that of starting microstructure with the value of 12.04%. The special grain boundary amount shows a minimum value for deformation at 925°C, and an increase when increasing deformation temperature to 960°C, The predominated types of special grain boundary include ∑5, ∑17a and ∑27a type at deformation temperature of 850°C and 960°C, and increasing deformation temperature to 960°C results in an relatively random distribution in special grain boundary. The special grain boundary shows an decrease when deformation amount increases firstly, then increase up to a maximum value at the 60% deformation amount; The predominated types of special grain boundary include ∑5, ∑17a and ∑27a type at deformation amount of 40% and 60%, and 80% deformation amount yields a relatively random distribution in special grain boundary. An increase of strain rate results in a decrease of special grain boundary and large angle grain boundary, while an increase of small angle boundary.