Effect of high-pressure torsion on microstructure, mechanical properties and corrosion resistance of cast pure Mg

© 2018, The Author(s). High-pressure torsion (HPT) processing was applied to cast pure magnesium, and the effects of the deformation on the microstructure, hardness, tensile properties and corrosion resistance were evaluated. The microstructures of the processed samples were examined by electron backscatter diffraction, and the mechanical properties were determined by Vickers hardness and tensile testing. The corrosion resistance was studied using electrochemical impedance spectroscopy in a 3.5% NaCl solution. The results show that HPT processing effectively refines the grain size of Mg from millimeters in the cast structure to a few micrometers after processing and also creates a basal texture on the surface. It was found that one or five turns of HPT produced no significant difference in the grain size of the processed Mg and the hardness was a maximum after one turn due to recovery in some grains. Measurements showed that the yield strength of the cast Mg increased by about seven times whereas the corrosion resistance was not significantly affected by the HPT processing

Optimizing Heat Treatment for Electroplated NiP and NiP/SiC Coatings

NiP (P > 10 wt.%) coatings are amorphous coatings whose structure can be transformed by heat treatment into a crystalline structure and hardened by precipitation of Ni3P. In this study, NiP coatings and composite ones with SiC nanoparticles were produced by electrodeposition, and their structural transformation by heat treatment was studied using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The microhardness and the scratch and corrosion resistance of the coatings were evaluated and compared before and after different heat treatments. The results showed that in as-plated condition, the addition of SiC particles in the coatings did not modify the microstructure, microhardness, or electrochemical behavior. However, the SiC particles’ role was disclosed in combination with heat treatment. Composite coatings that were heat treated at 300 °C had higher microhardness and scratch resistance than the pure NiP one. In addition, composite coatings maintained their scratch resistance up to 400 °C, while in the case of the NiP ones, there was a reduction in scratch resistance by heating at 400 °C. It was also concluded that heating temperature has the main role in hardness and corrosion resistance of NiP and composite coatings, rather than heating time. The optimum heat-treatment protocol was found to be heating at 360 °C for 2 h, which resulted in a maximum microhardness of about 1500 HV0.02 for NiP and its composite coating without sacrificing the corrosion resistance

Electrodeposition of High Entropy Alloy of Ni-Co-Cu-Mo-W from an Aqueous Bath

This study aimed to deposit high entropy alloy (HEA) coatings with five different elements, Ni, Co, Cu, Mo, and W, from a single aqueous bath. The influence of pH, current density, and complex agent on the composition of deposited coating was examined. It was shown that Mo and W were codeposited mainly with Ni and Co. pH had the most impact on the codeposition of reluctant elements like Mo and W, while current density had the minimum effect. The deposited coating had a metallic, dense, and nodular morphology with configurational entropy of around 1.6 R

Optimizing Heat Treatment for Electroplated NiP and NiP/SiC Coatings

NiP (P &amp;gt; 10 wt.%) coatings are amorphous coatings whose structure can be transformed by heat treatment into a crystalline structure and hardened by precipitation of Ni3P. In this study, NiP coatings and composite ones with SiC nanoparticles were produced by electrodeposition, and their structural transformation by heat treatment was studied using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The microhardness and the scratch and corrosion resistance of the coatings were evaluated and compared before and after different heat treatments. The results showed that in as-plated condition, the addition of SiC particles in the coatings did not modify the microstructure, microhardness, or electrochemical behavior. However, the SiC particles role was disclosed in combination with heat treatment. Composite coatings that were heat treated at 300 degrees C had higher microhardness and scratch resistance than the pure NiP one. In addition, composite coatings maintained their scratch resistance up to 400 degrees C, while in the case of the NiP ones, there was a reduction in scratch resistance by heating at 400 degrees C. It was also concluded that heating temperature has the main role in hardness and corrosion resistance of NiP and composite coatings, rather than heating time. The optimum heat-treatment protocol was found to be heating at 360 degrees C for 2 h, which resulted in a maximum microhardness of about 1500 HV0.02 for NiP and its composite coating without sacrificing the corrosion resistance.Funding Agencies|Horizon 2020 [686135]</p

Effect of SiC particle size and heat-treatment on microhardness and corrosion resistance of NiP electrodeposited coatings

Electrodeposition of NiP composite coatings with nano and sub-micron sized SiC has been carried out to investigate the possibility of replacing hard chromium coatings. The composition and structure of the coatings were evaluated by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis, respectively. Microhardness was measured by Vickers indentation and polarization measurements were carried out to study the corrosion behavior of the coatings. The results showed that submicron particles can be codeposited with a higher content as compared to nano sized ones. However, even if a smaller amount of the nano-sized SiC particles are incorporated in the coating, the contribution to an increasing microhardness was comparable with the submicron sized particles, which can be related to the higher density of codeposited particles. SiC particles did not change the anodic polarization behavior of NiP coatings in a 3.5% NaCl solution. Finally, the effect of heat-treatment on the coatings properties at 400 °C for 1 h was studied to investigate the contribution of particles and heat-treatment on hardness and corrosion properties. It was found that the heat-treatment doubled the microhardness and changed the anodic polarization behavior of the coatings from passive to active with respect to the as-plated conditions

Influence of friction stir processing conditions on corrosion behavior of AZ31B magnesium alloy

The present study aims to investigate the effect of friction stir processing (FSP) conditions on the corrosion characteristic of AZ31B magnesium alloy. Specimens made of AZ31B alloy were friction stir processed under various processing conditions, and their microstructure and corrosion behavior were studied. The corrosion behavior was studied by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and immersion test in 3.5% sodium chloride (NaCl) solution. The results showed a substantial improvement in the corrosion resistance of the friction stir processed AZ31B alloy. The improvement is likely a result of more stable corrosion products and microstructure refinement formed after friction sir processing. Keywords: Magnesium, Friction stir processing, Corrosion, Polarization, EI

The effect of co-deposition of SiC sub-micron particles and heat treatment on wear behaviour of Ni–P coatings

none6siThe purpose of the study is to assess the influence of SiC particles and heat treatment onthe wear behaviour of Ni–P coatings when in contact with a 100Cr6 steel. Addition of reinforcingparticles and heat treatment are two common methods to increase Ni–P hardness. Ball-on-disc weartests coupled with SEM investigations were used to compare as-plated and heat-treated coatings,both pure and composite ones, and to evaluate the wear mechanisms. In the as-plated coatings,the presence of SiC particles determined higher friction coefficient and wear rate than the pureNi–P coatings, despite the limited increase in hardness, of about 15%. The effect of SiC particleswas shown in combination with heat treatment. The maximum hardness in pure Ni–P coatingwas achieved by heating at 400◦C for 1 h while for composite coatings heating for 2 h at 360◦Cwas sufficient to obtain the maximum hardness. The difference between the friction coefficient ofcomposite and pure coatings was disclosed by heating at 300◦C for 2 h. In other cases, the coefficientof friction (COF) stabilised at similar values. The wear mechanisms involved were mainly abrasionand tribo-oxidation, with the formation of lubricant Fe oxides produced at the counterpart.mixedDonya Ahmadkhaniha; Lucia Lattanzi; Fabio Bonora; Annalisa Fortini; Mattia Merlin ; Caterina ZanellaAhmadkhaniha, Donya; Lattanzi, Lucia; Bonora, Fabio; Fortini, Annalisa; Merlin, Mattia; Zanella, Caterin

Effect of high-pressure torsion on microstructure, mechanical properties and corrosion resistance of cast pure Mg

Abstract High-pressure torsion (HPT) processing was applied to cast pure magnesium, and the effects of the deformation on the microstructure, hardness, tensile properties and corrosion resistance were evaluated. The microstructures of the processed samples were examined by electron backscatter diffraction, and the mechanical properties were determined by Vickers hardness and tensile testing. The corrosion resistance was studied using electrochemical impedance spectroscopy in a 3.5% NaCl solution. The results show that HPT processing effectively refines the grain size of Mg from millimeters in the cast structure to a few micrometers after processing and also creates a basal texture on the surface. It was found that one or five turns of HPT produced no significant difference in the grain size of the processed Mg and the hardness was a maximum after one turn due to recovery in some grains. Measurements showed that the yield strength of the cast Mg increased by about seven times whereas the corrosion resistance was not significantly affected by the HPT processing