Pub Date : 2023-07-25DOI: 10.1080/14786435.2023.2237900
H. Kumar, N. Esakkiraja, A. Dash, A. Paul, S. Bhattacharyya
ABSTRACT We propose a numerical inverse method based on physics-informed neural networks (PINN) for calculating composition-dependent diffusion coefficients in pseudo-binary (PB) diffusion couples in multicomponent alloys. Traditional methods rely solely on experimental diffusion profiles as design targets, which can lead to unreliable estimates. In contrast, PINN uses a combination of available data and physics-based constraints to obtain optimised design parameters and exact solutions for constrained governing differential equations. The constraints in PINN include governing partial differential equations, initial and boundary conditions, and any other equality/inequality relations obeyed by physical parameters. Our study shows the necessity of experimentally estimated intrinsic diffusion coefficients for the prediction of reliable composition-dependent mobility data. In the absence of such data, different combinations of unknown intrinsic diffusion coefficients can also produce reasonable approximations of diffusion profiles and interdiffusion coefficients while wrongly predicting more fundamental quantities (i.e. intrinsic diffusivities). Our method utilises PINN to simultaneously obtain optimised design parameters (diffusion coefficients) and exact solutions for governing diffusion equations. The implementation of PINN uses experimentally estimated diffusion coefficients obtained by the PB diffusion couple method, in addition to diffusion profiles, as design targets. The method is extended to non-ideal PB diffusion profiles, such as conventional diffusion couples in which all the components develop diffusion profiles, by incorporating additional constraints such as zero composition gradient of certain component(s) and experimentally estimated interdiffusion coefficients at extrema in the composition profiles. PINN is found to be a promising approach for obtaining reliable estimates of diffusion coefficients in multicomponent alloys.
{"title":"Utilising physics-informed neural networks for optimisation of diffusion coefficients in pseudo-binary diffusion couples","authors":"H. Kumar, N. Esakkiraja, A. Dash, A. Paul, S. Bhattacharyya","doi":"10.1080/14786435.2023.2237900","DOIUrl":"https://doi.org/10.1080/14786435.2023.2237900","url":null,"abstract":"ABSTRACT We propose a numerical inverse method based on physics-informed neural networks (PINN) for calculating composition-dependent diffusion coefficients in pseudo-binary (PB) diffusion couples in multicomponent alloys. Traditional methods rely solely on experimental diffusion profiles as design targets, which can lead to unreliable estimates. In contrast, PINN uses a combination of available data and physics-based constraints to obtain optimised design parameters and exact solutions for constrained governing differential equations. The constraints in PINN include governing partial differential equations, initial and boundary conditions, and any other equality/inequality relations obeyed by physical parameters. Our study shows the necessity of experimentally estimated intrinsic diffusion coefficients for the prediction of reliable composition-dependent mobility data. In the absence of such data, different combinations of unknown intrinsic diffusion coefficients can also produce reasonable approximations of diffusion profiles and interdiffusion coefficients while wrongly predicting more fundamental quantities (i.e. intrinsic diffusivities). Our method utilises PINN to simultaneously obtain optimised design parameters (diffusion coefficients) and exact solutions for governing diffusion equations. The implementation of PINN uses experimentally estimated diffusion coefficients obtained by the PB diffusion couple method, in addition to diffusion profiles, as design targets. The method is extended to non-ideal PB diffusion profiles, such as conventional diffusion couples in which all the components develop diffusion profiles, by incorporating additional constraints such as zero composition gradient of certain component(s) and experimentally estimated interdiffusion coefficients at extrema in the composition profiles. PINN is found to be a promising approach for obtaining reliable estimates of diffusion coefficients in multicomponent alloys.","PeriodicalId":19856,"journal":{"name":"Philosophical Magazine","volume":"115 1","pages":"1717 - 1737"},"PeriodicalIF":1.6,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90370336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-18DOI: 10.1080/14786435.2023.2211808
H. Saka, H. Iwata, M. Takagi
ABSTRACT Microstructure of laser induced modified volume (LIMV) in Si was examined using transmission electron microscopy (TEM) and infra-red optical microscopy. Dominant features of LIMV are voids, dislocations, cracks and non-DS phases of Si. Nucleation of dislocations and cracks can be accounted for by dilatation caused by local temperature rise near the focus of laser. Mass of Si wafer before and after laser injection was conserved by laser injection. Therefore, those Si atoms which must have existed in pre-void, that is, that area which on laser injection is transformed to void, also stay in Si matrix. The void is thermally stable up to ∼800oC, however, it becomes unstable above ∼800oC. That is, void (or LIMV) fades above ∼800oC under infra-red optical microscope. In TEM, after annealing at 1000oC, 1∼a few μm diameter voids which had been present in the as-laser-injected Si, disappeared and very fine voids (nano-voids) appeared. In the cross-sectional TEM of LIMV sitting near the exiting surface of laser beam, a gap was observed between the exiting surface and a protective coat (W). Si atoms in pre-void become plasmas on laser irradiation. In other words, Si atom is dissociated into Si+n and n free electrons (n =1 ∼ 14). The ionized Si (Si+n) forms a void but some of them are dispersed in the adjacent matrix of DS-Si. On the other hand, free electrons gain a high energy and travel far away from the void: The ionized Si (Si+n) and free electrons do not recombine to annihilate.
{"title":"Whereabouts of missing atoms in a laser-injected Si (Part III)","authors":"H. Saka, H. Iwata, M. Takagi","doi":"10.1080/14786435.2023.2211808","DOIUrl":"https://doi.org/10.1080/14786435.2023.2211808","url":null,"abstract":"ABSTRACT Microstructure of laser induced modified volume (LIMV) in Si was examined using transmission electron microscopy (TEM) and infra-red optical microscopy. Dominant features of LIMV are voids, dislocations, cracks and non-DS phases of Si. Nucleation of dislocations and cracks can be accounted for by dilatation caused by local temperature rise near the focus of laser. Mass of Si wafer before and after laser injection was conserved by laser injection. Therefore, those Si atoms which must have existed in pre-void, that is, that area which on laser injection is transformed to void, also stay in Si matrix. The void is thermally stable up to ∼800oC, however, it becomes unstable above ∼800oC. That is, void (or LIMV) fades above ∼800oC under infra-red optical microscope. In TEM, after annealing at 1000oC, 1∼a few μm diameter voids which had been present in the as-laser-injected Si, disappeared and very fine voids (nano-voids) appeared. In the cross-sectional TEM of LIMV sitting near the exiting surface of laser beam, a gap was observed between the exiting surface and a protective coat (W). Si atoms in pre-void become plasmas on laser irradiation. In other words, Si atom is dissociated into Si+n and n free electrons (n =1 ∼ 14). The ionized Si (Si+n) forms a void but some of them are dispersed in the adjacent matrix of DS-Si. On the other hand, free electrons gain a high energy and travel far away from the void: The ionized Si (Si+n) and free electrons do not recombine to annihilate.","PeriodicalId":19856,"journal":{"name":"Philosophical Magazine","volume":"16 1","pages":"1345 - 1359"},"PeriodicalIF":1.6,"publicationDate":"2023-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88820003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-10DOI: 10.1080/14786435.2023.2228214
Chao Jiang, Renqiang Jiao, Zhihong Zhang, Zhicong He, B. Dong
ABSTRACT Cu-W70-90 (wt.%) alloys were prepared by infiltration method, and the laser ablation experiments were conducted. The laser ablation resistance mechanism of Cu-W alloy was revealed with the guidance of the mathematic model coupling heat and fluid flow. By comprehensively analysing the calculation and the experimental results, the laser spot generated giant heat which will vaporise and melt the alloy respectively close to and away from the centre of the laser spot. The vaporisation of the alloy and the temperature gradient opposite to the laser propagation direction will significantly affect the flow field and make the molten alloy splash around. It was also quantitively proven that the W-rich phases with a high melting point can significantly increase the ablation resistance of Cu-W alloy by decreasing the ablation depth. The calculation results present a relatively high accuracy, this work will thus contribute to the application of the mathematic models in the laser processing field.
{"title":"A strategy to reveal the laser ablation resistance mechanism of Cu-W alloy: experiments and simulations","authors":"Chao Jiang, Renqiang Jiao, Zhihong Zhang, Zhicong He, B. Dong","doi":"10.1080/14786435.2023.2228214","DOIUrl":"https://doi.org/10.1080/14786435.2023.2228214","url":null,"abstract":"ABSTRACT Cu-W70-90 (wt.%) alloys were prepared by infiltration method, and the laser ablation experiments were conducted. The laser ablation resistance mechanism of Cu-W alloy was revealed with the guidance of the mathematic model coupling heat and fluid flow. By comprehensively analysing the calculation and the experimental results, the laser spot generated giant heat which will vaporise and melt the alloy respectively close to and away from the centre of the laser spot. The vaporisation of the alloy and the temperature gradient opposite to the laser propagation direction will significantly affect the flow field and make the molten alloy splash around. It was also quantitively proven that the W-rich phases with a high melting point can significantly increase the ablation resistance of Cu-W alloy by decreasing the ablation depth. The calculation results present a relatively high accuracy, this work will thus contribute to the application of the mathematic models in the laser processing field.","PeriodicalId":19856,"journal":{"name":"Philosophical Magazine","volume":"257 1","pages":"1691 - 1700"},"PeriodicalIF":1.6,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73518618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-09DOI: 10.1080/14786435.2023.2230461
D. Bejan, A. Radu, C. Stan
ABSTRACT In this paper, we theoretically studied a 3D structure of GaAs/Al0.3Ga0.7As triple concentric quantum rings submitted to the combined action of a non-resonant intense laser and a static electric field. The 3D model was built using the cross-sectional profile of the structure that corresponds to a realistic experimental case of triple rings with different heights and widths. The electric field and the laser field have opposite influence on the energy levels, decreasing or increasing all studied levels, respectively. Linear or quadratic Stark effect can be seen in specific ranges of electric field values, depending on the anisotropy induced by the intense laser field, for given fields orientations. The observed anti-crossings are explained by wave-functions delocalisation from one ring to another or by symmetry exchange between the wave-functions of the inner ring. For the most deformed potential created by perpendicular orientation of electric field and intense laser polarisation, very large absorption peaks, blue-shifts, red-shifts or an oscillatory behaviour in peaks energy and amplitude are obtained in a controllable way by proper manipulation of the fields. This can be helpful for the tunability and optical features improvement of THz detectors or solar cells.
{"title":"Electronic and optical responses of laser dressed triple concentric quantum rings in electric field","authors":"D. Bejan, A. Radu, C. Stan","doi":"10.1080/14786435.2023.2230461","DOIUrl":"https://doi.org/10.1080/14786435.2023.2230461","url":null,"abstract":"ABSTRACT In this paper, we theoretically studied a 3D structure of GaAs/Al0.3Ga0.7As triple concentric quantum rings submitted to the combined action of a non-resonant intense laser and a static electric field. The 3D model was built using the cross-sectional profile of the structure that corresponds to a realistic experimental case of triple rings with different heights and widths. The electric field and the laser field have opposite influence on the energy levels, decreasing or increasing all studied levels, respectively. Linear or quadratic Stark effect can be seen in specific ranges of electric field values, depending on the anisotropy induced by the intense laser field, for given fields orientations. The observed anti-crossings are explained by wave-functions delocalisation from one ring to another or by symmetry exchange between the wave-functions of the inner ring. For the most deformed potential created by perpendicular orientation of electric field and intense laser polarisation, very large absorption peaks, blue-shifts, red-shifts or an oscillatory behaviour in peaks energy and amplitude are obtained in a controllable way by proper manipulation of the fields. This can be helpful for the tunability and optical features improvement of THz detectors or solar cells.","PeriodicalId":19856,"journal":{"name":"Philosophical Magazine","volume":"94 1","pages":"1738 - 1755"},"PeriodicalIF":1.6,"publicationDate":"2023-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78710104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-09DOI: 10.1080/14786435.2023.2231863
N. Polushkin
ABSTRACT Bragg–Williams (BW) modelling is a mean-field approach to order–disorder phase transformations (ODPT´s) in substitutional alloys. While the BW theory itself is for thermal equilibrium, the relaxation of the alloy to the equilibrium state in terms of the BW approach was studied by Dienes who introduced the chemical balance equation for temporal evolution of the long-range order parameter S. Here, results of solving numerically the Dienes equation are presented, with taking additionally into account that ordering in the alloy occurs through vacancies in atomic lattice. In such a description there are three important parameters that affect the ordering kinetics, namely (1) the interdiffusion coefficient in a disordered alloy, (2) the ratio of initial to equilibrium (thermal) concentration of vacancies, r, and (3) the characteristic timescale τ∝L 2 for vacancy relaxation, where L is the effective distance between sinks/sources of vacancies in the alloy. With example of Fe-rich Fe aluminides Fe x Al1-x (x = 0.6), it is found that, at sufficiently large r, an additional step arises in temporal evolution of S for a time which can be much shorter (scaled as ∝r −1) than the characteristic timescale for ordering at r = 1. The height of this step increases up to unity at sufficient r. The lowest values of r and L are determined, at which non-equilibrium vacancies injected into the alloy can still play the role. This study would be of potential interest for developing the technology of functional alloys (lowering of ordering temperatures) and for obtaining a kind of information about vacancy behaviour in crystals.
Bragg-Williams (BW)模型是替代合金中有序-无序相变(ODPT)的一种平均场方法。虽然BW理论本身是用于热平衡的，但Dienes在BW方法中研究了合金到平衡状态的弛豫，他引入了长程有序参数s的时间演化的化学平衡方程。这里给出了数值求解Dienes方程的结果，并额外考虑了合金中的有序是通过原子晶格中的空位发生的。在这样的描述中，有三个重要的参数影响有序动力学，即(1)无序合金中的相互扩散系数，(2)空位初始与平衡(热)浓度的比值r，以及(3)空位弛豫的特征时间标度τ∝l2，其中L是合金中空位汇/源之间的有效距离。以富铁的Fe铝化物Fe x Al1-x (x = 0.6)为例，我们发现，当r足够大时，S的时间演化中会出现一个额外的步骤，其时间比r = 1时排序的特征时间标度要短得多(标为∝r−1)。当r足够大时，这一步骤的高度增加到1。确定了r和L的最低值，此时注入合金的非平衡空位仍然可以发挥作用。该研究对功能合金技术的发展(降低有序温度)和获得晶体中空位行为的一种信息具有潜在的意义。
{"title":"Quantifying the effect of non-equilibrium vacancies on Bragg–Williams ordering","authors":"N. Polushkin","doi":"10.1080/14786435.2023.2231863","DOIUrl":"https://doi.org/10.1080/14786435.2023.2231863","url":null,"abstract":"ABSTRACT Bragg–Williams (BW) modelling is a mean-field approach to order–disorder phase transformations (ODPT´s) in substitutional alloys. While the BW theory itself is for thermal equilibrium, the relaxation of the alloy to the equilibrium state in terms of the BW approach was studied by Dienes who introduced the chemical balance equation for temporal evolution of the long-range order parameter S. Here, results of solving numerically the Dienes equation are presented, with taking additionally into account that ordering in the alloy occurs through vacancies in atomic lattice. In such a description there are three important parameters that affect the ordering kinetics, namely (1) the interdiffusion coefficient in a disordered alloy, (2) the ratio of initial to equilibrium (thermal) concentration of vacancies, r, and (3) the characteristic timescale τ∝L 2 for vacancy relaxation, where L is the effective distance between sinks/sources of vacancies in the alloy. With example of Fe-rich Fe aluminides Fe x Al1-x (x = 0.6), it is found that, at sufficiently large r, an additional step arises in temporal evolution of S for a time which can be much shorter (scaled as ∝r −1) than the characteristic timescale for ordering at r = 1. The height of this step increases up to unity at sufficient r. The lowest values of r and L are determined, at which non-equilibrium vacancies injected into the alloy can still play the role. This study would be of potential interest for developing the technology of functional alloys (lowering of ordering temperatures) and for obtaining a kind of information about vacancy behaviour in crystals.","PeriodicalId":19856,"journal":{"name":"Philosophical Magazine","volume":"35 1","pages":"1775 - 1786"},"PeriodicalIF":1.6,"publicationDate":"2023-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80311048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-01DOI: 10.1080/14786435.2023.2227793
R. Vikram, K. Dash, Shanmukha Kiran Aramanda, S. Suwas
ABSTRACT A combined nickel–cobalt-based eutectic high entropy alloy (Ni-Co-based HEA) has been designed based on the valence electron concentration (VEC) value. The microstructure of the developed alloy consists of a face-centered cubic (FCC) and ordered cubic (B2) structure, which was validated using CALPHAD. The microstructure is hierarchical with length scales in micrometers (lamellar eutectic morphology) and nanometers (B2 length scale). B2 phase precipitation was observed in the supersaturated FCC primary phase. The orientation relationship (OR) between the phases exhibited a strong Kurdjimov-Sachs (KS) type OR, typical of FCC/BCC interface structures. This EHEA displayed good yield strength at room temperature and strain rate insensitivity in the 10−3–10−1 strain rate range. GRAPHICAL ABSTRACT
{"title":"Design of a nickel–cobalt based eutectic high entropy alloy (NiCo)1.7AlCrFe with hierarchical microstructural length scales","authors":"R. Vikram, K. Dash, Shanmukha Kiran Aramanda, S. Suwas","doi":"10.1080/14786435.2023.2227793","DOIUrl":"https://doi.org/10.1080/14786435.2023.2227793","url":null,"abstract":"ABSTRACT A combined nickel–cobalt-based eutectic high entropy alloy (Ni-Co-based HEA) has been designed based on the valence electron concentration (VEC) value. The microstructure of the developed alloy consists of a face-centered cubic (FCC) and ordered cubic (B2) structure, which was validated using CALPHAD. The microstructure is hierarchical with length scales in micrometers (lamellar eutectic morphology) and nanometers (B2 length scale). B2 phase precipitation was observed in the supersaturated FCC primary phase. The orientation relationship (OR) between the phases exhibited a strong Kurdjimov-Sachs (KS) type OR, typical of FCC/BCC interface structures. This EHEA displayed good yield strength at room temperature and strain rate insensitivity in the 10−3–10−1 strain rate range. GRAPHICAL ABSTRACT","PeriodicalId":19856,"journal":{"name":"Philosophical Magazine","volume":"64 1","pages":"1592 - 1602"},"PeriodicalIF":1.6,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73819406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-01DOI: 10.1080/14786435.2023.2231355
K. Jyotheender, Manu Mathai, S. K. Makineni, C. Srivastava
ABSTRACT ZnNi alloy coatings with low Ni content (1–4 wt.% Ni) were electrodeposited over mild steel. Ni addition changed the coating morphology from faceted to hillock, decreased the crystallite size, and shifted the basal plane texture to higher energy (01 1) texture. Zn-1.5 wt.% Ni coating exhibited significantly improved corrosion resistance, even better than the pristine Zn coating. The corrosion resistance properties, however, degraded considerably as the Ni content increased (2.7 and 3.7 wt% Ni). The high corrosion resistance of the Zn-1.5 wt.% Ni coatings was due to the presence of nearly basal texture, low coating strain and evolution of stable γ-phase in the Zn matrix. The corrosion rate for higher Ni addition increased due to high energy surface texture and higher coating strain.
{"title":"Nickel partitioning in ZnNi coatings (Ni less than 4 wt.%) and its effect on the coating corrosion behaviour","authors":"K. Jyotheender, Manu Mathai, S. K. Makineni, C. Srivastava","doi":"10.1080/14786435.2023.2231355","DOIUrl":"https://doi.org/10.1080/14786435.2023.2231355","url":null,"abstract":"ABSTRACT ZnNi alloy coatings with low Ni content (1–4 wt.% Ni) were electrodeposited over mild steel. Ni addition changed the coating morphology from faceted to hillock, decreased the crystallite size, and shifted the basal plane texture to higher energy (01 1) texture. Zn-1.5 wt.% Ni coating exhibited significantly improved corrosion resistance, even better than the pristine Zn coating. The corrosion resistance properties, however, degraded considerably as the Ni content increased (2.7 and 3.7 wt% Ni). The high corrosion resistance of the Zn-1.5 wt.% Ni coatings was due to the presence of nearly basal texture, low coating strain and evolution of stable γ-phase in the Zn matrix. The corrosion rate for higher Ni addition increased due to high energy surface texture and higher coating strain.","PeriodicalId":19856,"journal":{"name":"Philosophical Magazine","volume":"16 1","pages":"1701 - 1716"},"PeriodicalIF":1.6,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74948805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-22DOI: 10.1080/14786435.2023.2224092
Indrani Mukherjee, P. Das
ABSTRACT In this study, a comprehensive molecular dynamics (MD) study on the structural evolution of alumina nanoparticles during sintering has been performed using two-sphere model. The effect of variation in particle size and heating rate are investigated. A power-law equation is proposed to explain the increase of dimensionless neck radius, with the increasing sintering time. Two important parameters are extracted from the equation: a characteristic time related to the initiation of neck formation and an exponent related to the rate of neck growth. The variation of shrinkage and density of particles are also used to characterise the sintering of alumina nanoparticles. One of the novel findings is that instead of temporal variation of dimensionless neck radius, its variation with shrinkage can be used to correlate simulation and experimental results. From the results of the variation of heating rate, it is revealed that a lower heating rate initiates neck formation at a lower temperature. The sintering temperature has been successfully estimated for micron-sized particles from the results of molecular dynamics simulation using Herring’s scaling law. Moreover, it is evident from experimental validation that the developed MD model can successfully predict the average dimensionless neck size value of micro injection moulded alumina, at sintered state, and thereby can be effectively used as a process control tool.
{"title":"A molecular dynamics study of sintering of micro injection moulded alumina nano particles","authors":"Indrani Mukherjee, P. Das","doi":"10.1080/14786435.2023.2224092","DOIUrl":"https://doi.org/10.1080/14786435.2023.2224092","url":null,"abstract":"ABSTRACT In this study, a comprehensive molecular dynamics (MD) study on the structural evolution of alumina nanoparticles during sintering has been performed using two-sphere model. The effect of variation in particle size and heating rate are investigated. A power-law equation is proposed to explain the increase of dimensionless neck radius, with the increasing sintering time. Two important parameters are extracted from the equation: a characteristic time related to the initiation of neck formation and an exponent related to the rate of neck growth. The variation of shrinkage and density of particles are also used to characterise the sintering of alumina nanoparticles. One of the novel findings is that instead of temporal variation of dimensionless neck radius, its variation with shrinkage can be used to correlate simulation and experimental results. From the results of the variation of heating rate, it is revealed that a lower heating rate initiates neck formation at a lower temperature. The sintering temperature has been successfully estimated for micron-sized particles from the results of molecular dynamics simulation using Herring’s scaling law. Moreover, it is evident from experimental validation that the developed MD model can successfully predict the average dimensionless neck size value of micro injection moulded alumina, at sintered state, and thereby can be effectively used as a process control tool.","PeriodicalId":19856,"journal":{"name":"Philosophical Magazine","volume":"51 1","pages":"1626 - 1649"},"PeriodicalIF":1.6,"publicationDate":"2023-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74262950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-20DOI: 10.1080/14786435.2023.2221043
G. Kumar, Mrinal Phukon, C. Srivastava
ABSTRACT Cobalt coatings were electrodeposited at different deposition current densities (10 mA·cm−2, 20 mA·cm−2, 30 mA·cm−2, 40 mA·cm−2, 60 mA·cm−2) over mild steel substrate. The coating deposited at 30 mA·cm−2 showed the highest corrosion resistance (Rp = 7515Ω·cm2) due to a higher fraction of Low energy grain boundary constitution (i.e. coincidence site lattices (CSLs) and low angle grain boundaries (LAGB)) and exhibited higher fraction of stabler Co3O4 passive oxide layer. The coatings electrodeposited at 60 mAcm−2 exhibited lower corrosion resistance (Rp = 1304 Ω·cm2) due to a higher fraction of high-angle grain boundaries and a higher fraction of relatively lesser stable Co(OH)2.
{"title":"Deposition current density-induced grain boundary engineering of electrodeposited cobalt coatings for enhanced electrochemical stability","authors":"G. Kumar, Mrinal Phukon, C. Srivastava","doi":"10.1080/14786435.2023.2221043","DOIUrl":"https://doi.org/10.1080/14786435.2023.2221043","url":null,"abstract":"ABSTRACT Cobalt coatings were electrodeposited at different deposition current densities (10 mA·cm−2, 20 mA·cm−2, 30 mA·cm−2, 40 mA·cm−2, 60 mA·cm−2) over mild steel substrate. The coating deposited at 30 mA·cm−2 showed the highest corrosion resistance (Rp = 7515Ω·cm2) due to a higher fraction of Low energy grain boundary constitution (i.e. coincidence site lattices (CSLs) and low angle grain boundaries (LAGB)) and exhibited higher fraction of stabler Co3O4 passive oxide layer. The coatings electrodeposited at 60 mAcm−2 exhibited lower corrosion resistance (Rp = 1304 Ω·cm2) due to a higher fraction of high-angle grain boundaries and a higher fraction of relatively lesser stable Co(OH)2.","PeriodicalId":19856,"journal":{"name":"Philosophical Magazine","volume":"24 1","pages":"1553 - 1576"},"PeriodicalIF":1.6,"publicationDate":"2023-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81490402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-11DOI: 10.1080/14786435.2023.2219463
Srishti Mishra, S. Pal
ABSTRACT Influence of configurational design of single crystal Al-Al90Sm10 metallic glass nanolaminates on torsion deformation behaviour of Al/Al90Sm10 nanolaminate (Configuration 1) and Al90Sm10/Al nanolaminate (Configuration 2) from a structural evolution aspect have been analysed by employing Molecular Dynamics for a torsion speed of 1/600 revolution/ps. Adaptive common neighbour (a-CNA) analysis, Dislocation extraction algorithm (DXA), atomic shear strain analysis, and Voronoi Polyhedral (VP) analysis have been carried out to reveal the structural evolution in the nanolaminates specimen subjected to torque. As a consequence of dislocation density localisation under torsional loading in Al/Al90Sm10 nanolaminate high atomic strain gradient is developed in the nanolaminate specimen causing torsional buckling of the Al/Al90Sm10 nanolaminate. The localisation of dislocation density rings induces the formation of dislocation substructure in Al/Al90Sm10 nanolaminate. The crystalline/amorphous interface serves as a free surface and encourages the formation of such dislocation substructure. The collective nucleation, coalescence, and growth of shear transformation zones (STZs) leading to the formation of thick shear bands on either end of Al90Sm10/Al nanolaminate inducing an almost homogenous atomic strain gradient across the surface of the nanolaminate specimen thereby averting torsional buckling. The C/A interface serves as a nucleation site for the generation STZs in Al90Sm10/Al nanolaminate. VPs such as <0, 0, 4, 6>, <0, 3, 6, 4>, <0, 3, 6, 5> <0, 2, 8, 2> have the load bearing capacity and are resistant to fragmentation under the subjugation of torsion loading.
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