Work

Interrupted in-situ X-ray computed tomography reveals accelerated densification in recovered 7055 Al powder

Year: 2026

Type: article

Abstract: • Recovered AA7055 powder exhibits ∼50% faster peak densification rate and 10 × higher total effective diffusivity than commercial powder. • In-situ curvature mapping quantitatively confirms accelerated pore evolution, with pore rupture initiating 25°C earlier in recovered powder. • Morphology-driven Laplace stress concentrations (>1.5 MPa) at neck regions promote asymmetric growth and multi-neck interconnection, accelerating pore collapse. • First 3D demonstration of Laplace stress-mediated densification mechanism linking particle geometry to cooperative fusion kinetics in irregular powders. Efficient recovery of aluminum alloy powder represents a critical challenge in powder metallurgy, particularly given that irregular morphology and broad particle size distribution in recovered powders induce complex sintering behaviors not yet fully understood. In this study, in-situ X-ray computed tomography was employed to systematically investigate the densification mechanisms of commercial gas-atomized and spray-forming-recovered 7055 aluminum powders during hot-press sintering. Results demonstrate that despite 10.6% lower initial packing density, recovered powder exhibits ∼50% faster peak densification rate and order-of-magnitude higher total effective diffusivity. Three-dimensional pore analysis confirms a classical “cup-saddle-cap” evolution pathway in both systems, but recovered powder initiates pore rupture 25°C earlier, accelerates spheroidization, and enhances multi-neck interconnection, primarily attributable to irregular particle geometry and packing heterogeneity. Laplace stress mapping further reveals sustained local stress concentrations (>1.5 MPa) at neck regions, promoting asymmetric neck growth and multi-neck interconnection, which collectively accelerate pore closure and overall densification. This work establishes a direct microstructure-property linkage between particle morphology, stress fields, and densification kinetics, providing fundamental insights for the high-value utilization of recovered aluminum powders.

Source: Materials & Design

DOI: 10.1016/j.matdes.2026.115484