Micropillar Compression Study on the Deformation Behavior of Electrodeposited Ni–Mo Films

Jenő Gubicza,László Péter,Garima Kapoor,János L Lábár,György Radnóczi,Dávid Ugi

doi:10.3390/coatings10030205

Abstract

The influence of Mo addition on the compression behavior of Ni films was studied by micropillar deformation tests. Thus, films with low (0.4 at.%) and high (5.3 at.%) Mo contents were processed by electrodeposition and tested by micropillar compression up to the plastic strain of about 0.26. The microstructures of the films before and after compression were studied by transmission electron microscopy. It was found that the as-deposited sample with high Mo concentration has a much lower grain size (~26 nm) than that for the layer with low Mo content (~240 nm). In addition, the density of lattice defects such as dislocations and twin faults was considerably higher for the specimen containing a larger amount of Mo. These differences resulted in a four-times higher yield strength for the latter sample. The Ni film with low Mo concentration showed a normal strain hardening while the sample having high Mo content exhibited a continuous softening after a short hardening period. The strain softening was attributed to detwinning during deformation.

Highlights

IntroductionCurie temperature decreases significantly with increasing Mo concentration in Ni [1]
Alloying with Mo is an effective way to tailor the physical properties of Ni
The deformation behaviors of nanocrystalline Ni films deposited with low and high Mo contents were studied by micropillar compression test which was performed up to the plastic strain of 0.26

Summary

Introduction

Curie temperature decreases significantly with increasing Mo concentration in Ni [1]. The hardness and the wear resistance of Ni considerably increase with the addition of Mo, Ni–Mo alloys are often used as hard coatings [2]. The improvement of hardness and wear resistance with grain refinement is a general phenomenon for Ni-based coatings, be achieved either with alloying or with incorporation of ceramic particles [3]. Alloying may result in the decrease of the grain size and in the increase of the lattice defect density [4]. In dispersion-hardened coatings, the primary hardening factor is the grain refinement as a result of the particle incorporation, regardless of the properties of the particles incorporated [3]

Methods

Discussion

Conclusion