Tieli Chen

Synthesis of nanocrystalline TiC powder by mechanical alloying

Synthesis of nanocrystalline TiC was investigated. The raw powders are Ti and C element, respectively. The ratio of Ti and C elements is 1:1 (mol). Mechanical alloying has been applied to obtain nanocrystalline TiC. The microstructure of nanocrystalline TiC has been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the nanocrystalline TiC powder was fabricated by mechanical alloying in a very short time at room temperature. The formation mechanism is self-propagating reactive synthesis conducted by mechanical alloying.

Bulk Nanocrystalline Cu Produced by High-Energy Ball Milling

The preparation, mechanical properties, grain size and thermal property of bulk nanocrystalline Cu (BNC-Cu) were investigated in this paper. BNC-Cu can be produced by in situ consolidation of pure Cu powder with high-energy ball milling at room temperature; the average grain sizes of Cu samples decreased with the increasing of ball milling time before 9 h because the grain refining velocity was bigger than the grain growing velocity in this stage. When the ball milling time was beyond 9 h, the average grain size reached a steady minimum value about 27.5 nm. The microhardness of BNC-Cu samples increased with the extending of ball milling time in the first 9 h because the dominating factor was the hardening effect caused by grain refinement and work hardening rather than softening in this stage. BNC-Cu gained its highest microhardness about 1.59GPa when the ball milling time reached 9 h. Subsequently, the microhardness of BNC-Cu slightly fluctuated around this value. Because there were numerous triple grain boundaries and the interaction among different crystal defects in BNC-Cu, BNC-Cu showed outstanding thermal stability when it was annealed in the range of 100°C to 400°C.