Pure tantalum (Ta) is widely used in applications such as capacitors and semiconductor coatings due to its high melting point, excellent corrosion resistance, and good biocompatibility. In this study, spark plasma sintering (SPS) technology has been employed to successfully prepare high-density, fine-grained pure Ta through systematic optimization of sintering temperature, pressure, and holding time. The results indicate that sintering temperature plays a predominant role on the densification behavior. Increasing the sintering pressure and prolonging the holding time also contribute to further enhancing the densification. Under the process conditions of 1450 °C, 40 MPa, and a holding time of 10 min, the relative density of the sample reaches 98.7%. Microstructural analysis reveals that the sintering process of pure Ta can be divided into two main stages: densification-dominated and grain growth-dominated. When the relative density exceeds a threshold value (approximately 96% in this study), the grain size increases rapidly from 4.43 μm to 28.87 μm. This grain coarsening leads to a transition in the fracture mechanism from a mixed mode of intergranular and cleavage fractures to completely intergranular fracture, which significantly reduces the bending strength and plastic deformation capacity of the material.
Huang et al. (Thu,) studied this question.