We performed density functional calculations to estimate the formation energies of intermetallic alloys. We used two semilocal approximations, the generalized gradient approximation (GGA) by Perdew-Burke-Ernzerhof (PBE) and the strongly constrained and appropriately normed (SCAN) meta-GGA. In addition, we utilized two nonlocal DFT functionals, the hybrid HSE06, and the state-of-the-art random phase approximation (RPA). The nonlocal functionals such as HSE06 and RPA yield accurate formation energies of binary alloys with completely-filled d-band metals, where semilocal functionals underperform. The accuracy at the nonlocal functionals is greatly reduced when a partially-filled d-band metal is present in an alloy, while PBE-GGA outperforms in these cases. We show that the accurate prediction of formation energies by any DFT method depends on its ability to predict the accurate electronic properties, e.g., valence d-band contribution to the density of states (DOS). The SCAN meta-GGA often corrects the PBE-DOS, however, it does not provide accurate formation energies compared to PBE. This is assumed to be due to the lack of proper error cancellation that should be expected due to the similar bulk nature of both alloys and their constituents, which may improve with the modification of meta-GGA ingredients. RPA yields too negative formation energies of alloys with partially-filled d-band metals. RPA results can be corrected by restoring the exchange-correlation kernel, thereby improving the short-range electron-electron correlation in metallic densities.
The mechanical behavior of two nanocrystalline Al alloys, Al-Mg-Y and Al-Fe-Y, is investigated with in-situ micropillar compression testing. Both alloys were strengthened by a hierarchical microstructure including grain boundary segregation, nanometer-thick amorphous complexions, carbide nanorod precipitates with sizes of a few nanometers, and submicron-scale intermetallic particles. The maximum yield strength of the Al-Mg-Y system is measured to be 950 MPa, exceeding that of the Al-Fe-Y system (680 MPa), primarily due to a combination of more carbide nanorods and more amorphous complexions. B…
Intermetallic phases in a recently developed Al-Li-Cu-Mg alloy have been investigated to understand their roles in the initiation and propagation processes of intergranular corrosion. Corrosion initiation involves trenching formation in the Al matrix adjacent to the large particles of Al7Cu2(Fe, Mn) phases. These phases containing Li are electrochemically active and susceptible to self-dissolution via a de-alloying mechanism during corrosion process. The subsurface particles of Al7Cu2(Fe, Mn) and Al20Cu2Mn3 phases act as the internal cathodes for continuous corrosion propagation along the part…
Light-weight alloys are essential pillars of transportation technologies. They also play a crucial role to achieve a more green and cost-effective aerospace technologies. Magnesium-lithium-aluminum (Mg-Li-Al) alloys are auspicious candidates due to their promising mechanical strengths at low densities. We herein present a systematic first-principles investigation of the Mg-Li-Al-based alloys to provide insights for designing ultra-strong light-weight alloys. Initial analysis indicates that the Mg-Li-Al mixtures are not thermally stabilized into random-solid solutions. Following this hint, the …
Magnesium (Mg) alloys have shown great prospects as both structural and biomedical materials, while poor corrosion resistance limits their further application. In this work, to avoid the time-consuming and laborious experiment trial, a high-throughput computational strategy based on first-principles calculations is designed for screening corrosion-resistant binary Mg alloy with intermetallics, from both the thermodynamic and kinetic perspectives. The stable binary Mg intermetallics with low equilibrium potential difference with respect to the Mg matrix are firstly identified. Then, the hydroge…
Synchrotron X-ray tomography investigation of 3D morphology of intermetallic phases and pores and their effect on the mechanical properties of cast Al-Cu alloys
The microstructure of Mg-Al-Ca alloys consists of a hard intra- and intergranular eutectic Laves phase network embedded in a soft $α$-Mg matrix. For such heterogeneous microstructures, the mechanical response and co-deformation of both phases under external load are not yet fully understood. We therefore used nano- and microindentation in combination with electron microscopy to study the deformation behaviour of an Mg-3.68Al-3.8Ca alloy. We found that the hardness of the Mg$_2$Ca phase was significantly larger than the $α$-Mg phase and stays constant within the measured temperature range. The …
The lattice dynamics of Cu3Au, Ni70Pt30, Pd90Fe10, and Pd96Fe04 intermetallic is studied using the DFT calculations. We calculated the phonon dispersions and phonon densities of states along two high symmetry paths of the Brillouin zone by Weighted Dynamical Matrix (WDM) approach. We also compared the results with the supercell approach and inelastic neutron scattering. Furthermore, we calculated the impact of mass and force-constant fluctuations on the Cu3Au and made a comparison with both WDM and supercell approaches results. The averaged first Nearest Neighbor (1NN) force constants between …
We study a cast Mg-4.65Al-2.82Ca alloy with a microstructure containing $α$-Mg matrix reinforced with a C36 Laves phase skeleton. Such ternary alloys are targeted for elevated temperature applications in automotive engines since they possess excellent creep properties. However, in application, the alloy may be subjected to a wide range of strain rates and in material development, accelerated testing is often of essence. It is therefore crucial to understand the effect of such rate variations. Here, we focus on their impact on damage formation. Due to the locally highly variable skeleton formin…
The lattice dynamics of AgPd, Ni55Pd45, Ni95Pt05, and Cu0.715Pd0.285 intermetallic have been investigated using the DFT calculation. The phonon dispersions and phonon densities of states along for two symmetry directions are calculated by Weighted Dynamical Matrix (WDM) and compared with virtual crystal approximation (VCA), supercell approach, and inelastic neutron scattering experimental results. The impact of mass, force-constant fluctuation, and Ag concentration on lattice dynamics of AgPd are discussed, and a comparison between WDM and Supercell approach is performed. The averaged first Ne…
In view of the long-standing controversy over the reversibility of transition metals in Sn-based alloys as anode for Li-ion batteries, an in situ real-time magnetic monitoring method was used to investigate the evolution of Sn-Co intermetallic during the electrochemical cycling. Sn-Co alloy film anodes with different compositions were prepared via magnetron sputtering without using binders and conductive additives. The magnetic responses showed that the Co particles liberated by Li insertion recombine fully with Sn during the delithiation to reform Sn-Co intermetallic into stannum richer phase…
In this present investigation, we discussed the synthesis, microstructure, and hydrogen storage behavior intermetallic Laves phase in a hexanal TiVZrMnCoFe high entropy alloy. In this HEA, three elements are hydride-forming elements and the other three are non-hydride-forming elements (Fe, Mn, Co). The thermodynamic parameter like enthalpy of mixing was calculated using Meidmas model.The possibility of developing high entropy Laves phase-based hydrogen storage materials was advocated.
Electric field gradients in Zr$_8$Ni$_{21}$ and Hf$_8$Ni$_{21}$ intermetallic compounds; Results from perturbed angular correlation measurements and first-principles density functional theory
Ni基Zr和Hf金属间化合物合金的大量技术应用促进了通过扰动角相关（PAC）光谱对Zr $_8$ Ni $_{21}$和Hf $_8$ Ni $_{21}$的全面研究，这在本报告之前没有研究。通过粉末活性炭（PAC）和X射线衍射（XRD）分析，确定了样品中的不同物相。利用$^{181}$ Hf探针，在Zr-$_8$-Ni $_{21}$和Hf-$_8$-Ni $_{21}$化合物中观察到两个非等价的Zr/Hf位.从目前Zr $_8$ Ni $_{21}$中的PAC测量，还观察到由于从液态金属通过共晶反应产生Zr $_7$ Ni $_{10}$而产生的组分。然而，从XRD测量中未发现相Zr $_7$ Ni $_{10}$。在Zr $_8$中，Ni $_{21}$在973 K之前没有明显的变化，但在1073 K时变化很大.在铪$_8$镍$_{21}$，两个非等效网站的类似结果已被发现，但网站分数是在相反的顺序。在该合金中，可能由于HfNi $_3$而导致的不同污染相已从PAC测量中发现，但未从XRD测量中发现。基于密度泛函理论计算了$^{181}$ Ta探针核上的电场梯度（EFG）和不对称性参数（$η$），并将所观察到的EFG组分归属于（Zr/Hf）$_8$ Ni $_{21}$化合物中的不同晶格位置.
Two intermetallic FeAl compounds with Al content of 70.68 and 72.17 at.pct were studied using Mössbauer spectroscopy (5 to 296 K) and X-ray diffraction (15 to 300 K). The compounds were found to crystallize in the orthorhombic Cmcm space group (eta-phase). The collected data revealed that dynamics of the Fe atoms (harmonic in entire temperature range) is significantly different that Al atoms. For the latter strong anharmonicity was evidenced. Moreover, it was found that partial filling of the different Al sites leads to occurrence of low and high symmetry coordination of Fe atoms, which was re…
In the use of hydrogen as large-scale energy vector, metal hydrides based on intermetallic compounds play a key role, thanks to mild temperatures and pressures required for the storage. It is increasingly necessary to develop hydrogen-based devices, and in this work, the intermetallic compound TiFe$_{0.85}$Mn$_{0.05}$ is evaluated and selected as H$_2$-carrier for a storage system of 50 kg of H$_2$. A batch of 5 kg of alloy was synthesized at industrial level and characterized through scanning electron microscopy and powder X-ray diffraction, to determine the structure and phase abundance. Mor…
Differential thermal analysis and solution growth of intermetallic compounds
为了通过溶液生长获得单晶，需要在适当但通常未知的平衡合金相图中暴露的初级凝固表面。此外，一个适当的坩埚材料是必要的，在生长过程中保持熔融合金，而不被攻击it.Recently，我们已经使用的比较现实的模拟与实验差热分析（DTA）曲线来解决这两个问题。我们发现：1）可以解释复杂的DTA曲线，以确定适当的热处理和溶液生长的起始组成，而不必详细确定基础相图。2)差热分析可以帮助鉴别合适的坩埚材料。因此，DTA可用于使通过溶液生长获得所需相的单晶的过程更有效。我们将使用一些系统，我们最近获得了单晶样品，使用DTA和溶液生长的组合作为例子。这些系统是TbAl、Pr $_7$ Ni $_2$ Si $_5$和YMn $_4$ Al $_8$。
Lattice Parameter is an important material feature in High Entropy Alloy (HEA) Design. Vegards Law is typically used to estimate lattice parameters but is often inaccurate for metal alloys due to an inability to account for charge transfer which can affect atomic volumes. The present study used ab initio simulation to calculate bond lengths between atoms of dissimilar elements in B2 intermetallic compounds which was then combined with a bond counting model to produce a model to estimate the lattice parameters of Refractory BCC HEAS. The model was tested using a supercell method which modeled v…
Developing a single-phase and nanograined refractory high-entropy alloy ZrHfNbTaW with ultrahigh hardness by phase transformation via high-pressure torsion
