Mechanically induced self-propagating reaction and consequent consolidation for the production of fully dense nanocrystalline Ti55C45 bulk material

Abstract

We employed a high-energy ball mill for the synthesis of nanograined Ti55C45 powders starting from elemental Ti and C powders. The mechanically induced self-propagating reaction that occurred between the reactant materials was monitored via a gas atmosphere gas-temperature-monitoring system. A single phase of NaCl-type TiC was obtained after 5h of ball milling. To decrease the powder and grain sizes, the material was subjected to further ball milling time. The powders obtained after 200h of milling possessed spherical-like morphology with average particle and grain sizes of 45μm and 4.2nm, respectively. The end-products obtained after 200h of ball milling time, were then consolidated into full dense compacts, using hot pressing and spark plasma sintering at 1500 and 34.5MPa, with heating rates of 20°C/min and 500°C/min, respectively. Whereas hot pressing of the powders led to severe grain growth (~436nm in diameter), the as-spark plasma sintered powders maintained their nanograined characteristics (~28nm in diameter). The as-synthesized and as-consolidated powders were characterized, using X-ray diffraction, high-resolution electron microscopy, and scanning electron microscopy. The mechanical properties of the consolidated samples obtained via the hot pressing and spark plasma sintering techniques were characterized, using Vickers microhardness and non-destructive testing techniques. The Vickers hardness, Young's modulus, shear modulus and fracture toughness of as-spark plasma sintered samples were 32GPa, 358GPa, 151GPa and 6.4MPa·m1/2, respectively. The effects of the consolidation approach on the grain size and mechanical properties were investigated and are discussed.