AbstractIn studies of the fracture surfaces of tensile, Charpy V-notch, and crack opening displacement (COD) fracture toughness specimens, taken from metal inert gas (MIG) welds fabricated in commercial purity titanium plate, an unusual form of fracture mode was observed. The feature took the form of shallow troughlike grooves and has been termed‘fluting’. By careful matching of the opposite faces of sectioned fractured specimens, and using stereofractography, it has been shown that the flutes consist of the ruptured halves of hexagonal shaped voids that formed before the final failure of the specimen. Titanium hydrides, which occur in the weld metal as impurities, have been used to show that there is a definite crystallographic relationship between the occurrence of flutes and the matrix. Although flutes were observed both with cleavage and with dimpled areas of fracture, they are the manifestation of a ductile fracture mode and form by a dislocation mechanism involving {1010}〈1210〉slip.MST/916