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In this study, we applied potentiodynamic polarization to the analysis of surface corrosion in a 2017‐T4 alloy during a stress corrosion cracking (SCC) test in 1 m NaCl solution. A constant load SCC test was chosen, classifying the applied load into three categories – no load, medium load, and high load – with the material's yield strength as a maximum load. Electrochemical measurements carried out during the SCC test allowed us, by plotting the current density versus the applied potential on a logarithmic scale, to determine the electrochemical characteristic parameters for each load category. These parameters, combined with both cross‐sectional and surface morphological analysis, were used to qualitatively characterize the corrosion of the aluminum alloy. All tests performed revealed two different attack behaviors, one characterized by shallow pits and the other by a deep, intergranular penetration. The presence of each behavior depends on the intensity of the applied load, which involves variations in the polarization curve and therefore modifies the electrochemical parameters. Copyright © 2016 John Wiley & Sons, Ltd.

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This paper will focus on the effect of deep cryogenic treatment (DCT) on the microstructure, mechanical properties and stress corrosion cracking susceptibility of a heat-treated aluminium alloy. The different microstructures have been characterized by X-ray diffraction, optical microscope, scanning electron microscope and transmission electron microscope. The stress corrosion cracking susceptibility of the alloy, before and after the DCT, in chloride solution was examined using slow strain rate test (SSRT) method at various strain rates. The results show that the sub-zero treatment increases the secondary non-coherent nanoparticles at the grain boundary, and this slight precipitation did not produce any modification of the mechanical properties. Furthermore the compressive residual stresses of the material were higher after than before the treatment. Both these effects are the responsible for an improvement of the stress corrosion cracking behaviour of this alloy after DCT.

A high power diode laser has been used for surface melting of a 7075-T6 aluminium alloy in order to induce changes in the microstructure, which could lead to an improvement of its corrosion performance. The treatment produces a fine dendritic microstructure region at the surface, whose depth depends mostly on the temperature at the surface of the material and, only marginally, on the scanning speed of the laser beam. An analysis of the microstructure and second phases before and after the surface treatment is presented in this paper.

We applied a laser surface melting treatment to AISI M2 high-speed steel and studied the resulting surface characteristics (microstructure) and mechanical behavior (hardness and wear performance). The steel was treated using an Nd : YAG continuouswave laser with different scanning speeds and power densities. The influence of the laser processing parameters on the melted surface layer was studied. The microstructure was characterized using optical microscopy, scanning electron microscopy and X-ray diffraction. We also assessed the effects of overlapping on the microstructure and the mechanical properties of the wear-resistant surface.

SummaryWe describe the microstructure of Nd:YAG continuous wave laser surface melted high-speed steel, namely AISI M2, treated with different laser scanning speeds and beam diameters on its surface. Microstructural characterization of the remelted surface layer was performed using light optical and scanning electron microscopy and X-ray diffraction. The combination of the three techniques provided new insights into the substantial changes induced by laser surface melting of the steel surface layer. The advantage of the method is that it avoids the difficult and tedious work of preparing samples of this hard material for transmission electron microscopy, which is the technique normally used to study these fine microstructures. A melted zone with a dendritic structure and a partially melted zone with a heterogeneous cellular structure were observed. M 2 C carbides with different morphologies were identified in the resolidified surface layer after laser melting.

Laser surface melting (LSM) using a high power diode laser was used to modify the surface of AA 2017-T4 alloy. The first part of this work concerns the applicability of diode laser to surface melting of the AA2017-T4 alloy. Irradiation conditions were varied to investigate the effect of process parameters on the treated surface. The results show that the application of diode laser makes treating the surface of this alloy possible. Microstructural characterisation of the bulk material and the remelted surface layer was performed using scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The combination of the three techniques allows the identification of the intermetallic compounds -down to nanometre size -in the surface layer.