Structural-Phase States of Titanium After an Electroexplosive Alloying and the Subsequent Electron-Beam Treatment

Abstract

The features of a surface relief, structure and phase composition of the hardened layers of commercially pure titanium after electroexplosive aluminizing and boroaluminizing with the subsequent electron-beam treatment are studied by methods of scanning and transmission electron-diffraction microscopies. The distribution of microhardness in depth is studied. As shown, the combined treatment leads to formation of a low roughness of a surface and is characterized by small quantity of microcracks. The total depth of a zone of influence at aluminizing and boroaluminizing is 60 and 90 μm, respectively. The microhardness of a surface increases in 2.3 and 5.5 times, accordingly. Along the depth of the combined-treatment zone, three layers naturally connected with each other are observed: the near-surface layer, which has a boundary determined by the depth of the electron-beam treatment; the intermediate layer with the changed phase composition caused by the electroexplosive alloying; the layer of a thermal influence, in which the hardening is reached due to the structure–phase changes of an alloy base. As revealed, the hardening under electroexplosive aluminizing and electron-beam treatment is reached due to formation of the multiphase structure containing nanoand microcrystalline particles of intermetallic compounds of the titanium–aluminium system; under boroaluminizing, the aluminium and titanium borides of various morphology are also revealed.

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