Alloys, Metals, Metallurgical Materials Testing

Lu, Dujiang, et al. Materials Science and Engineering: B 263 (2021): 114838.

This study explores the optimization of Al-Si precursor alloys for dealloying, focusing on the critical role of melt fragility in determining the alloy composition. The Al-Si eutectic alloy, known for its minimal melt fragility, was found to exhibit the best structural properties, evolving into a honeycomb-like nanoporous Si with a large specific surface area. This unique structure significantly enhances its potential for various applications, particularly in energy storage.

The investigation demonstrated that the melt fragility of Al-Si alloys directly influences the morphology of dealloyed products. The Al-Si eutectic alloy formed a nanoporous structure with continuous ligaments and abundant pores, which was advantageous for lithium-ion battery anodes. When tested as an anode material, the nanoporous Si12 anode showed superior cycling performance and higher capacity retention compared to Si7 and Si20 anodes. This finding underscores the importance of melt fragility in predicting the optimal composition for dealloying, offering a more reliable and efficient approach than the traditional trial-and-error method.

By predicting the ideal precursor alloy composition, this research provides valuable guidelines for the development of advanced energy storage materials. The hierarchical nanoporous structure of the Si12 anode, combined with high porosity, makes it a promising candidate for applications requiring stable and efficient energy storage solutions.

Duschek, L., et al. Ultramicroscopy 200 (2019): 84-96.

This study presents an advanced method for determining the composition of alloys using Scanning Transmission Electron Microscopy (STEM) high-angle annular dark-field (HAADF) images, coupled with complementary multislice simulations. The method focuses on achieving high lateral resolution and single-atom accuracy for the composition determination of alloy systems, addressing both theoretical capabilities and intrinsic limitations.

Through simulations, the study highlights the accuracy of the method in determining the composition of materials, such as (Ga,In)As, within different sample thicknesses. Results show that a correct composition determination can be achieved with sample thicknesses up to three atoms, with deviations becoming more pronounced at greater thicknesses. This is attributed to overlapping intensity ranges for different numbers of substitute atoms, leading to potential over- or underestimation of the local composition. Despite these challenges, the method provides accurate global composition determination, particularly when sample thickness is correctly assumed.

The method was applied to three technologically important semiconductor alloy systems—(Ga,In)As QWs, Ga(P,As), and SiGe QWs—demonstrating good agreement with HRXRD measurements and strain state analysis. With atomic lateral resolution and insensitivity to surface relaxation, this method is invaluable for analyzing alloys with gradients in composition or interface roughness, advancing the characterization of complex alloy systems that traditional XRD cannot accurately resolve.

Kaya, H. A. S. A. N., E. Çadırlı, and A. H. M. E. T. Ülgen. Materials & Design 32.2 (2011): 900-906.

This study investigates the effects of copper composition on the microhardness, electrical resistivity, and thermal properties of high-purity Zn-Cu alloys. Directionally solidified alloys with copper contents of 0.7, 1.5, 2.4, and 7.37 wt.% Cu were tested under two different solidification conditions. The microhardness (HV) values showed a clear dependence on copper content, increasing with higher copper concentrations. The relationship between microhardness and copper content (Co) was established as HVT = 56.10 Co^0.19 for solidification condition G = 3.85 K/mm, V = 0.0083 mm/s, and HVT = 69.36 Co^0.18 for G = 8.70 K/mm, V = 0.436 mm/s.

Electrical resistivity (ρ) and conductivity (σ) measurements revealed that resistivity increased and conductivity decreased with rising temperature, consistent with literature data. The temperature coefficient of resistivity (α) also increased with copper content at constant temperatures.

Thermal analysis, conducted using differential scanning calorimetry (DSC), showed that the melting temperature of the Zn-Cu alloys rose with increasing copper content, from 697.34 K for 0.7 wt.% Cu to 703.35 K for 7.37 wt.% Cu. Additionally, the enthalpy of fusion (ΔH) and specific heat (Cp) values decreased with higher copper concentrations.

These findings provide essential insights into the influence of copper composition on the mechanical, electrical, and thermal properties of Zn-Cu alloys, which are valuable for applications requiring specific material characteristics.