The present work focused on corrosion inhibition of AA6063 type (Al-Mg-Si) alloy in sodium chloride (NaCl) solution with a silicon carbide inhibitor, using the potentiodynamic electrochemical method. The aluminium alloy surface morphology was examined, in the as-received and as-corroded in the un-inhibited state, with scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS). The results obtained via linear polarization indicated a high corrosion potential for the unprotected as-received alloy. Equally, inhibition efficiency as high as 98.82% at 10.0 g/v silicon carbide addition was obtained with increased polarization resistance (Rp), while the current density reduced significantly for inhibited samples compared to the un-inhibited aluminium alloy. The adsorption mechanism of the inhibitor aluminium alloy follows the Langmuir adsorption isotherm. This shows that the corrosion rate of aluminium alloy with silicon carbide in NaCl environment decreased significantly with addition of the inhibitor.

Corrosion Resistance ofAA6063-Type AI-Mg-Si Alloy by Silicon Carbide in Sodium Chloride Solution for Marine Application

Electrically assisted (EA) microforming has pervasive benefits for the fabrication of high-performance microproducts. In this research, the coupled effect between the microstructural size effect and pulsed current on the flow characteristics of 304 stainless steel sheets along thickness direction was explored by using EA micro-compression tests. The results revealed that the strain hardening rate and the deformation stress of 304 stainless steel decreases during the EA deformation, especially when the current density exceeds 57.16 A/mm2. Besides, the effect of grain size on the micro-scaled compression is gradually weakened with the augment of current density and plastic strain. The electron backscatter diffraction (EBSD) results showed in the perspective of microstructure that the decrease of flow stress and strain hardening rate with the rise of pulsed current density is related to the reduction of dislocation density and texture strength due to the dynamic recrystallization during EA deformation. The pulsed current suppresses the grain refinement of fine-grained material and promotes that of coarse-grained material, and the recrystallization rate of EA deformation increases with the decrease of initial grain size. In addition, the recrystallization texture induced by the pulsed current can promote grain deflection and weakens the effect of twins in coarse-grained material. That can explain the reason for the weakening of the grain size effect. The findings in the research have important guiding significance for understanding the coupled mechanism of electroplastic and grain size effect on the flow characteristics of difficult-to-deform material, and further promoting the application of EA micro-rolling of high-strength materials.

Flow characteristics and microstructural evolution in pulsed current assisted micro-scaled compression of stainless steel sheet

Dislocation density based modelling of electrically assisted deformation process by finite element approach

Volume fraction effect of stainless steel on microstructure, interface, corrosion and wear behavior of stainless steel / aluminum bimetal composites

There has been a widespread increase in the use of aluminum alloys in automotive industries for meeting ever-growing light-weighting requirements. However, edge formability is a critical manufacturing challenge that restricts their widespread use. Edge formability of sheet metal is determined using a hole expansion test (HET) and is evaluated by the hole expansion ratio (HER). The present study investigates the effect of temper conditions on the edge formability of AA7075 alloy sheets. Hole expansion tests were conducted in different temper such as W-temper (super saturated solid solution followed by water quenching), under aged (UA), and peak aged (PA) conditions. Two different hole preparation techniques, a punching and a drilling process, were used to prepare samples with varying edge conditions. The results demonstrate that the W-temper has the highest edge formability irrespective of hole edge conditions. Researchers have reported that uniaxial stress state prevails at the hole edge during the HET. Consequently, uniaxial tensile tests were conducted on for each temper condition and various tensile properties such as yield stress (YS), ultimate tensile strength (UTS), ratio of yield stress to ultimate tensile strength (YS/UTS) were determined to evaluate edge formability. Furthermore, microstructural and failure analysis of the failed specimens were performed to explain the deformation behavior during the HET.

https://doi.org/10.1088/1757-899x/1238/1/012038

Evaluation of hole expansion formability of high strength AA7075 alloy under varying temper conditions

The flow stress reduction during plastic deformation superposed with electric current, commonly referred as ‘electroplasticity’ has been actively researched over the past few decades. While the existence of an electron–dislocation interaction, independent of Joule heating is established, the exact rate controlling mechanism of the observed behaviour lacks consensus. Understanding the governing mechanism is complex due to the combined effect of Joule heating and electron–dislocation interaction. The present work attempts to establish the electroplastic mechanism in AA 6063 alloy and its nanocomposites. The role of microstructure on the electron interaction is investigated by preparing four distinct microstructure from the base alloy. All the samples were subjected to constant amplitude direct current during plastic deformation. The Joule heating effect is decoupled using the experimentally measured temperature history. The potential electroplastic mechanism for the alloy is elucidated by analysing the trend of flow stress reduction with strain and strain rate. It is inferred that micro Joule heating and electron wind effect cannot completely explain the observed electroplastic behaviour in AA 6063. The SiC particles in nano-composites suppressed the electroplastic effect. The observed mechanical behaviour under electric current is in agreement with the trend predicted assuming magnetic depinning mechanism. The reduction of dislocation density quantified using X-ray diffraction is found to concur with the inferred mechanism.

Padma Pratheesh

Papers

Microstructure dependent electroplastic effect in AA 6063 alloy and its nanocomposites