Revolutionising inverse design of magnesium alloys through generative adversarial networks

The utility of machine learning (ML) techniques in materials science has accelerated materials design and discovery. However, the accuracy of ML models - particularly deep neural networks - heavily relies on the quality and quantity of the training data. Data collection methods often have limitations arising from cost, difficulty, and resource-intensive human efforts. Thus, limited high-quality data, especially for novel materials, poses a significant challenge in developing reliable ML models. Generative adversarial networks (GANs) offer one solution to augment datasets through synthetic sample generation. The present work explores the application of GANs in magnesium (Mg) alloy design, by training two deep neural networks within the structure of a Wasserstein GAN to generate new (novel) alloys with desired mechanical properties. This data augmentation-based strategy contributes to model robustness, particularly in cases where traditional data collection is impractical. The approach presented may expedite Mg alloy development, through a GAN assisted inverse design approach.Comment: 23 pages, 4 figures, 2 tables, 1 Github repositor

Electrochemical Response of AA7075-T651 Following Immersion in NaCl Solution

The electrochemical behavior of AA7075-T651 following immersion in quiescent 0.1M NaCl is presented. Electrochemical impedance at various polarization intervals was determined using Fourier transformation of potentiostatically induced current transients. This allowed for rapid determination of the impedance response at fixed intervals revealing a more detailed insight into the kinetic response of the alloy when assessed with complementary analysis tools such as potentiodynamic testing. This led to a discussion regarding aspects of dissolution phenomena prior to alloy breakdown and at short immersion times

Microstructure and corrosion evolution of additively manufactured aluminium alloy AA7075 as a function of ageing

Additively manufactured high strength aluminium alloy AA7075 was prepared using selective laser melting. High strength aluminium alloys prepared by selective laser melting have not been widely studied to date. The evolution of microstructure and hardness, with the attendant corrosion, were investigated. Additively manufactured AA7075 was investigated both in the as-produced condition and as a function of artificial ageing. The microstructure of specimens prepared was studied using electron microscopy. Production of AA7075 by selective laser melting generated a unique microstructure, which was altered by solutionising and further altered by artificial ageing - resulting in microstructures distinctive to that of wrought AA7075-T6. The electrochemical response of additively manufactured AA7075 was dependent on processing history, and unique to wrought AA7075-T6, whereby dissolution rates were generally lower for additively manufactured AA7075. Furthermore, immersion exposure testing followed by microscopy, indicated different corrosion morphology for additively manufactured AA7075, whereby resultant pit size was notably smaller, in contrast to wrought AA7075-T6.Comment: 37 pages, includes 4 Tables and 11 Figure

Corrosion behavior of Mg-3Gd-1Zn-0.4Zr alloy with and without stacking faults

To develop biodegradable magnesium alloy with desirable corrosion properties, a low Gd-containing Mg–3Gd–1Zn–0.4Zr (wt%, GZ31K) alloy was prepared. The as-cast ingot was solution treated and then hot extruded. Microstructures were characterized by scanning electron microscopy (SEM). Corrosion behavior of the alloy under each condition was studied by hydrogen evolution and quasi in-situ corrosion methods. It has been found that the as-cast alloy is composed of α-Mg, stacking faults (SFs) at the outer edge of the matrix grains, and eutectic phase along the grain boundaries. After solution treatment, the SFs disappear and precipitates rich in Zn and Zr elements form in the grain interior and boundaries. The microstructure is significantly refined after extrusion. Hydrogen evolution tests show that the as-cast alloy exhibits the best corrosion resistance, and the solution-treated alloy has the worst corrosion resistance. Corrosion rate of the alloy under each condition decreases first and then increases with prolonging immersion time. Corrosion experiments demonstrate that α-Mg was corroded preferentially, the eutectic phase and precipitates exhibit better corrosion resistance. The as-extruded alloy demonstrates uniform corrosion due to fine and homogeneous microstructure.This project was supported by the Natural Science Foundation of Jiangsu Province for Outstanding Youth (BK20160081), the Natural Science Foundation of Higher Education Institutions of Jiangsu Province – Key Project (18KJA430008), the Jiangsu Government Scholarship for Overseas Studies, the “333 Project” of Jiangsu Province (BRA2018338), the National Natural Science Foundation of China (51701093), and the Outstanding Scientific and Technological Innovation Team in Colleges and Universities of Jiangsu Province

Effects of Waveform and Cycle Period on Corrosion-Fatigue Crack Growth in Cathodically Protected High-Strength Steels

Abstract. The processes involved in corrosion fatigue in general are briefly outlined, followed by a brief review of recent studies on the effects of cycle frequency (rise times) and electrode potential on crack-growth rates at 'intermediate' ∆K levels for cathodically protected high-strength steels. New studies concerning the effects of fall times and hold times at maximum and minimum loads on crack-growth rates (for K max values below the sustained-load SCC threshold) are presented and discussed. Fractographic observations and the data indicate that corrosion-fatigue crack-growth rates in aqueous environments depend on the concentration of hydrogen adsorbed at crack tips and at tips of nanovoids ahead of cracks. Potential-dependent electrochemical reaction rates, crack-tip strain rates, and hydrogen transport to nanovoids are therefore critical parameters. The observations are best explained by an adsorption-induced dislocation-emission (AIDE) mechanism of hydrogen embrittlement. Review of Mechanisms and Some General Aspects of Corrosion Fatigue For many materials, embrittling environments (e.g. aqueous, gaseous hydrogen, liquid metals) can increase rates of fatigue crack growth by up to several orders of magnitude compared with the rate in inert environments, with the degree of embrittlement depending on variables such as ∆K, cycle frequency, and the 'potency' of the environment. In addition, the fracture path and fracturesurface appearance can be markedly different in inert and embrittling environments Fatigue crack growth at intermediate ∆K, for both inert and embrittling environments, generally involves plastic blunting and crack growth during the rising load part of each stress cycle, with resharpening of the crack tip occurring by deformation just behind crack tips during unloading. The difference between crack growth in inert and embrittling environments is that slip is more localised for the latter, resulting in less blunting and greater crack-growth increments for a given crack-tipopening displacement The localisation of plasticity and increased crack growth rates in both aqueous and gaseous hydrogen environments for many materials (e.g. Fe, Mg, Ni, Ti) are generally associated with an effect of atomic hydrogen, chemically or electrochemically generated by dissociation of water, or by dissociation of hydrogen molecule

Education CoDesign Workshops Report

As part of the Reimagine Initiative of the ANU College of Engineering and Computer Science (CECS), we conducted two (half-day) workshops in July and August 2019 with 40 CECS academic and professional staff to begin cross-College conversations about our education priorities in the coming years. The workshops brought together diverse views and experiences to explore both what is currently happening, as well as desires of what may happen in future in relation to the design challenge "What approaches to teaching and learning will we use in the reimagined College of Engineering and Computer Science?". The aim of the Reimagine Education CoDesign workshops were to articulate the values and approaches to education for the future of CECS and to begin to identify the structural and functional supports needed to enact these priorities. Specifically, the goal was to develop a set of common design challenges and then identify which are the highest priorities that the College can now work on. Some of these design challenges may already be in process, some may need more data and design work to address them and some may not be being addressed at all yet. These workshops provided an opportunity to uncover, discuss and prioritise these design challenges from the staff perspective. This report documents the process and outcomes of these workshops.This report was commisioned by ANU College of Engineering and Computer Scienc

High-temperature oxidation behaviour of AlxFeCrCoNi and AlTiVCr compositionally complex alloys

Compositionally complex alloys (CCAs), also termed as high entropy alloys (HEAs) or multi-principal element alloys (MPEAs), are being considered as a potential solution for many energy-related applications comprising extreme environments and temperatures. Herein, a review of the pertinent literature is performed in conjunction with original works characterising the oxidation behaviour of two diverse Al-containing alloys; namely a lightweight (5.06 g/cm(3)) single-phase AlTiVCr CCA and a multiple-phase Al0.9FeCrCoNi CCA (6.9 g/cm(3)). The thermogravimetric results obtained during oxidation of the alloys at 700 and 900 degrees C revealed that both alloys tended to obey the desired parabolic rate law. Post-exposure analysis by means of electron microscopy indicated that while the oxide scale formed on the AlTiVCr is adherent to the substrate, the scale developed on the Al0.9FeCrCoNi displays a notable spalling propensity. This study highlights the need for tailoring the protective properties of the oxide scale formed on the surface of the CCAs

Electrosprayed PLGA smart containers for active anti-corrosion coating on magnesium alloy Amlite

A novel self-healing system, consisting of poly(lactic-co-glycolic) acid (PLGA) porous particles loaded with a corrosion inhibitor, i.e. benzotriazole (BTA), has been successfully achieved via direct electro-spray deposition and subsequent epoxy spraying upon magnesium (Mg) alloy AMlite. The two-step process greatly simplified the multi-step fabrication of smart coatings reported previously. The PLGA particles demonstrate rapid response to both water and pH increase incurred by corrosion of Mg, ensuring instant and ongoing release of BTA to self-heal the protective functionality and retard further corrosion. Furthermore, nanopores in the PLGA–BTA microparticles, formed by the fast evaporation of dichloromethane during the electrospray process, also contribute to the fast release of BTA. Using Mg alloy AMlite as a model substrate which requires corrosion protection, potentiodynamic polarisation characterisation and scratch testing were adopted to reveal the anti-corrosion capability of the active coating