X-ray diffraction (XRD) profile analysis of pure ECAP-annealing Nickel samples

Abstract

X-Ray Diffraction (XRD) profile of pure equal channel angular pressing (ECAP)-annealing nickel samples has been thoroughly investigated for studying the material structures changes that imply to the mechanical behavior. Nickel-based material can be used for several applications such as biomaterial, gear, and some part of the instrument at nuclear facilities, which require high-grade standard material properties. ECAP is one kind of severe plastic deformation (SPD) techniques to obtain excellent mechanical properties without adding another element. However, the ECAP process generates metastable structures due to some mismatch structure and inhomogeneous stress within the material. This problem can usually be resolved by annealing after the ECAP process. In this article, pure Nickel was processed by ECAP at 423 K for two passes. The post-ECAP annealed will be carried out at the temperature range from 298 K until 1373 K. The microhardness test results indicate that the ECAP process increases the microhardness significantly, which remains stable after annealing until 773 K. At higher annealing temperature, the mechanical properties will drop suddenly and reach the microhardness value of pure pre-ECAP Nickel. This behavior could be explained clearly by the XRD data analysis result, which shows similar behavior structure changes. XRD data initially show peak shifting to lower 2θ value, which indicates an expansion to a higher lattice parameter, then at the higher annealing temperature, the diffraction peaks split gradually. This peak splitting could be indexed as pure pre-ECAP Ni peaks, which could be related to the drop of the microhardness value.