Microstructure and physical-mechanical properties evolution of pure tantalum processed with hard cyclic viscoplastic deformation

Abstract

The techniques of equal channel angular pressing and hard cyclic viscoplastic deformation were used to make changes in the microstructure and physical-mechanical properties of commercially pure tantalum. For the experiments, we used double electron beam melted oligocrystalline tantalum billet that was previously heat treated at 1100 °C for 1 h and processed by equal channel angular pressing with a wide range of equivalent von Mises strain (ℇVM = 0÷13.8) imposed on materials. At follows, the samples with stepped cross sections were tested on a materials testing setup Instron-8516 at room temperature. These changes in tantalum were determined depending on the tension-compression strain amplitude, strain rate, cycling frequency and number of cycles. The effects of processing routines on changes in the microstructure were investigated using scanning electron microscope and X-ray techniques. The mechanical and physical properties changes were characterized using hardness, density and electrical conduction measure techniques. The fracture mechanics change was studied by mini samples tensile testing up to fracture. The results show that during hard cyclic viscoplastic deformation of equal channel processed samples, with different processing histories, the tensile strength, hardness, plasticity, density, electrical conductivity, Young's modulus, etc. are changed. These changes in tantalum were characterized and analyzed.