In this prospective paper, we first review the existing simulation tools to simulate microgalvanic corrosion during free immersion. Then, we describe a recently developed application that employs PRISMS-PF, an open-source, high-performance phase-field modeling framework. The model employed in the application accounts for the electrochemical reaction at the metal/electrolyte interface and ionic migration in the electrolyte to determine the evolution of the corrosion front. We present the implementation details for the application and discuss its features such as super-linear parallel scaling performance for a sufficiently large system. Finally, we demonstrate the capability of the application by simulating corrosion of the matrix phase of an alloy near a secondary phase particle in two and three dimensions.
Graphical abstract
Evolution of nitrogen under shock compression up to 100 GPa is revisited via molecular dynamics simulations using a machine-learned interatomic model. Our model is shown capable of recovering the structure, dynamics, speciation and kinetics in hot compressed liquid nitrogen predicted by first- principles molecular dynamics, as well as the experimentally determined principal shock Hugoniot. We find that a purely molecular dissociation description of nitrogen chemistry provides an incomplete picture, and that short oligomers form in non-negligible quantities; no evidence is found for shock- induced cooling upon re-shocking.
In the tight reservoirs of Ordos Basin, shale interlayers are abundant. The mechanical properties of interlayers are different greatly from the adjacent sandstones, affecting the vertical propagation of hydraulic fractures, and resulting in a poor reservoir simulation with conventional hydraulic fracturing. The cyclic fracturing is an effective method to improve the efficiency of stimulation in such reservoirs. To verify the penetrating feasibility of hydraulic fractures with the cyclic fracturing and the conventional hydraulic fracturing, stimulation tests with true triaxial stresses are used to simulate the cyclic hydraulic fracturing in outcrop blocks of 300 × 300 × 600 mm. Hydraulic fractures form in the shale interlayer and penetrates both neighboring layers of sandstones. From visual observations and 3D scanning of the fractures, hydraulic fracture penetrations shows that: (1) Hydraulic fractures in the shale interlayer are complex, and a series of horizontal fractures along the bedding exist, which makes it difficult for fractures penetrate into the adjacent sandstones with conventional hydraulic fracturing; (2) Different from conventional hydraulic fracturing, hydraulic fractures can penetrate the neighboring sandstones from shale interlayer with the cyclic fracturing.
Magnesium and its alloys are the lightest structural metallic materials known, and therefore, hold vast potential for reducing the weight for various transportation modes such as airplanes, cars, buses, etc. Although the alloying of Mg with elements such as Al, Mn, and rare earth elements is known to improve the mechanical properties of Mg, the process is often detrimental to the corrosion performance of Mg. This increase in the corrosion rate occurs because of the microgalvanic couple that forms between the Mg-rich phase, which acts as an anode, and the alloying-element-rich phase, which acts as a cathode. Using both experiments and modeling, it has been reported that the rate of microgalvanic corrosion in the Mg alloys depends on the alloying element and microstructure. However, a deeper understanding is required for quantifying the effect of microstructure characteristics such as the fraction of the two phases, spacing between the two phases, the geometry of the two phases, etc., on the corrosion rate. This understanding is crucial for designing Mg alloys with optimal mechanical properties and high corrosion resistance. To bridge this gap in our understanding, we perform the continuum-scale phase-field modeling of different microstructures observed in Mg alloys. Furthermore, we complement the modeling work with theoretical analysis, where we develop analytical relations for studying the effect of various material and microstructural parameters on the characteristic corrosion length scale. The results from both these efforts will be summarized in our presentation.
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