Effect of mechanical milling atmosphere on hardness and constituent phases of pure titanium

Abstract

Effect of the mechanical milling conditions on hardness and constituent phase of pure titanium was investigated. The mechanical milling atmosphere and amounts of stearic acid, added as a process control agent (PCA), were varied. The hardness of mechanically milled (MMed) pure titanium powders in the air atmosphere was approximately 15% higher than that in the argon atmosphere. The mean particle size of the MMed powders in the air atmosphere was smaller compared to that in the argon atmosphere. The MMed pure titanium powders produced by two different atmospheres had almost the same constituent phase. The MMed powders were consolidated into bulk materials by spark plasma sintering (SPS). The hardness of the SPS materials produced from the MMed powder in the air atmosphere was 13% higher than that in the argon atmosphere. The amount of oxygen in the SPS materials significantly increased by the MM processing in the air atmosphere. The mean grain size of the SPS materials showed approximately 1 μm. The SPS materials were mainly strengthened by both solution hardening of oxygen and grain refinements.