Effect of Pressure and Heating Temperature on the Structure and Mechanical Properties of Explosion-Welded Aluminum-Niobium Multilayer Composite

Multilayer composites formed by explosion welding from alternated plates of niobium and aluminum are studied. The samples are subjected to annealing at 700, 800 and 900°C under a load and without load. The structure, the ultimate tensile strength, the impact toughness and the Vickers microhardness of the composites are determined. It is shown that mixed zones represented by nonequilibrium phases, intermetallic particles of NbAl₃ and Nb₂ Al, and undissolved niobium volumes are formed near “local melting/rapid solidification” interfaces. Increase of the annealing temperature from 700 to 900°C causes growth of the intermetallic inclusions, appearance of cracks in the reaction layer, and considerable worsening of the mechanical properties. The highest ultimate strength (700 MPa) and impact toughness (86 J/cm² ) are obtained in the samples annealed under pressure at 900 and 800°C, respectively. Annealing at 700°C at a pressure of 30 MPa is shown to be an optimum treatment producing a favorable effect on the strength characteristics and providing a defect-free structure.