Heat Treatment Regulates ‘As-Compacted’ Powder Inherited Microstructure and Mechanical Property Characteristics: A Case Study of Cold-Sprayed Metal Matrix Composites

The ‘Cold Spray plus’ approach, a key direction for cold spray technology, necessitates research on the ‘as-compacted’ powder characteristics within deposits. These characteristics inherently influence the microstructure and properties under thermal conditions. The response of typical as-compacted powder features to heat was investigated using Al₂O₃/2024 metal matrix composite as an example, with particular focus on particle bonding and mechanical properties. Our findings reveal that heat promotes a transition from mechanical interlocking to metallurgical bonding and defect formation, especially at high temperatures. Heat treatment eliminates work hardening, reducing hardness, which aging cannot fully restore. Consequently, wear mechanisms shift, with delamination and adhesive wear at defects dominating post HT. Remarkably, HT enhances tensile properties, with a 32% increase in ultimate strength to 368 MPa and an elongation of 1.58% at 300 °C. This is primarily due to increased metallurgical bonding, though defects remain a limiting factor for further improvement.