Chapter 6 - Enhanced mechanical properties of pure titanium based on solid-state reactions during a combination of mechanical milling and spark plasma sintering process

Abstract

Pure titanium powder was mechanically milled (MMed) with stearic acid, added as a process control agent (PCA), by using a vibrational ball mill, and MMed powders were subsequently consolidated into bulk materials by spark plasma sintering (SPS) in order to enhance the hardness and strength of pure titanium. Changes in the hardness, constituent phases, and powder particle size of the MMed powders have been examined by microhardness measurements, X-ray diffraction, and scanning electron microscopy (SEM), respectively. The hardness and microstructure of the SPS materials have also been studied by hardness measurements and optical microscopy. The Vickers microhardness of the pure titanium powders with 0.25g of PCA increased sharply from 189HV to 513HV after 8h of the mechanical milling (MM) process. Formation of TiH2 as the solid-state reaction product occurred in the MMed powder during 4 and 8h of the MM process. SEM observations revealed that pure titanium powders became finer powder particles from 24μm to 10μm after 8h of the MM process. The near full density was obtained for the SPS materials under the condition of an applied pressure at 49MPa with a sintering temperature at 1073K for 0.5h. The Vickers hardness of the SPS material fabricated from 8h MMed powder with 0.50g of PCA exhibited a maximum value of 1253HV.