Microstructure of Explosively Bonded Metals as Observed by Transmission Electron Microscopy (1st Report)

Microstructure of explosively bonded composites, low carbon-steel to low carbon-steel and austenitic stainless steel to low carbon-steel, has been investigated by transmission electron microscopy. The bond zone whose width is less than several μ consists of a mixture of a clad metal and a base metal, and the small crystal grains in each component metal are several thousand A in size. Both areas within about 10 μ from the bond zone are composed of either small crystal grains or elongated grains of several thousand A width. Dislocation density in these areas as well as the bond zone is of the order of 109/cm2. Larger crystal grains at distance of 10-600 μ from the bond zone has a dislocation density of 1010-1011/cm2, and the dislocation density at further increased distance is 109-1010/cm2. There exist tangled dislocations with cusps, dislocation loops and undeveloped cell structure. Thin deformation twins in austenitic stainless steel and elongated subgrains resulting from α→e→α transformation of low carbon-steel are observed profusely. No significant hcp e-phase is detected in the stainless steel.The adequacy of the proposed mechanism of the explosive bonding based on the theory of compressible fluid is discussed from the result obtained.