Materials Characterization最新文献

In this study, the effect of homogenization treatments (single and double stage) on the wire + arc additively manufactured (WAAM) 2319 aluminum (Al) alloy were analyzed. This involved an in-depth study on the diffusion and dissolution of eutectic phases (α(Al) + θ(Al₂Cu)) in the matrix using microstructural characterization techniques (DSC, XRD, optical and electron microscopy). Homogenization treatment parameters (temperature and time) were pre-determined based on DSC analyses. These parameters were later confirmed using homogenization kinetics calculations. A single-stage homogenization at 530 °C/24 h facilitated an almost complete diffusion of θ phase, but some of them remained undissolved at the grain boundaries. This treatment resulted in the reduction of hardness, ultimate tensile strength and yield strength by 26.0 %, 28.5 % and 28.8 %, respectively. A double-stage homogenization at 480 °C/8 h + 530 °C/24 h facilitated diffusion of Cu and dissolution of θ phases. This treatment improved the elongation (by 2.8 %), while the hardness, ultimate tensile strength and yield strength was still reduced by 28.7 %, 28.3 % and 26.2 %, respectively. θ phase at the grain boundaries almost disappeared, with several small θ phase particles remained within the grain. The homogenization treatments eliminated the segregation of θ phase and Cu element formed during the additive manufacturing (AM) process, improved the homogeneity of the WAAM 2319 Al alloy microstructures but with a compromise in the mechanical properties.

Hollow-strut metal lattices are novel cellular materials. Compared to their solid-strut counterparts, their powder bed fusion additive manufacturing (PBF-AM) features remain largely uninvestigated. This work focuses on characterizing the hollow-strut internal channel and nodal profiles, the defects and microstructures of the hollow-strut thin walls, and the inner surface conditions of the LPBF-manufactured body-centred cubic (BCC) Ti-6Al-4V hollow-strut lattices with different relative densities. BCC lattices are selected because of the low inclination angle (35.26°) of their constituent struts. These low-inclination hollow struts are designed using a recent model developed for PBF of inclined solid struts, together with considerations to prevent powder occlusion and ensure easy removal of powder particles. Detailed characterization indicates that our design considerations resulted in high-quality hollow-strut BCC Ti-6Al-4V lattices, which provide useful design insights for PBF-AM of hollow-strut metal lattices. In terms of microstructure, the Ti-6Al-4V hollow-strut thin walls (≤ 0.5 mm thick) exhibited different microstructures compared with Ti-6Al-4V solid struts, due to the heat accumulation effect in the inner channels. The implications are discussed for in-situ microstructure control.

This study addresses the critical need for lead-free solder alternatives in electronic manufacturing by investigating the microstructural characteristics of Sn-Ag solder alloys, focusing on the Ag₃Sn intermetallic phase. Utilizing Small-Angle Neutron Scattering (SANS), the study explored the phase interface and grain structure within Sn-Ag alloy to identify attributes that influence mechanical stability and performance. The research was structured around a comprehensive SANS analysis, complemented by Electron Backscatter Diffraction (EBSD) to expose the morphology and orientation of crystalline phases within the material. The investigation revealed distinct scattering patterns indicative of a multi-phase structure with a homogeneous distribution of fine Ag₃Sn precipitates within a β-Sn matrix. EBSD data confirmed these findings, showing a wide range of grain sizes and a random orientation distribution that matches theoretical models for polycrystalline materials. Notably, the SANS data uncovered a specific size distribution of the Ag₃Sn phase, which was characterized by a sharp interface contrast against the β-Sn matrix, pivotal for understanding the solder's mechanical properties. Interpretation of the SANS and EBSD data sets suggests that the Sn-Ag alloy's performance is significantly influenced by the dispersion and morphology of the Ag₃Sn phase. The presence of nanoscale Ag₃Sn structures, exhibiting a needle-like surface, implies a material optimized for mechanical reinforcement, which is essential for robust electronic connections. The integrated approach offers a novel perspective on the nano structural arrangement of lead-free solders, contributing to the advancement of safer, more reliable electronic materials. The findings have significant implications for the development of next-generation electronic components, reinforcing the transition to environmentally benign manufacturing processes.