Spark Plasma Sintering of Ti-1Al-8V-5Fe Alloy: Densification Mechanism and Grain Growth

The Ti-1Al-8V-5Fe (Ti185) alloys were prepared by spark plasma sintering (SPS) from TiH2, FeV, Al and Fe powders. The densification mechanism and grain-growth behavior of as-sintered alloys during SPS were investigated at temperatures of 800-1200 degrees C. A modified creep model considering liquid phase is proposed to modify the deviation of effective stress. The result shows that liquid phase caused by low-melting-point elemental powder can increase the effective stress, which enhances the particle rearrangement and densification. Densification stage at low temperature (800-1000 degrees C) without obvious grain growth and grain growth stage at 1100-1200 degrees C were identified during SPS process. At early densification stage, it is controlled by diffusion-controlled grain boundary sliding where the stress exponentnis close to 1, while at next stage, it is dominated by dislocation-climbing corresponding to thenclose to 3. The grain-growth mechanism of SPS Ti185 during grain-growth stage was under the control of bulk and grain boundary diffusion.