In situ scanning electron microscopy observations of tensile deformation in a boron-modified Ti–6Al–4V alloy

In situ scanning electron microscopy was performed during both room temperature and 480 °C tensile deformation of a boron-modified Ti–6Al–4V alloy, in order to characterize the deformation evolution. The sequence of observable surface deformation events was: TiB whisker microcracking at stresses well below the global yield stress, multiple and extensive TiB cracking after global yielding, α + β phase slip emanating from the cracked TiB whiskers, localized shear band formation and propagation leading to cracking in the α + β phases, and ductile sample failure. TiB cracking was also observed throughout the subsurface locations on post-deformed samples. The early microcracking of TiB particles did not degrade mechanical properties, and higher tensile and ultimate strengths were obtained with a ductile fracture mode at quasi-static tensile elongations equivalent to conventional Ti–6Al–4V.