Fusion zone shapes in electron-beam welding dissimilar metals

Experiments on welding dissimilar metals, such as aluminum or copper to iro n with an electron-beam welder, are conducted. It is found that the observe d depth-to-width ratio of the fusion zone in aluminum can be greater than u nity while that in iron is around unity. The former is attributed to the fo rmation of a cavity resulting from a high vapor pressure. The difference in depths increases with beam power. The observed depth-to-width ratios of fu sion zones in welding copper to iron can be greater than unity. A unique ma ximum depth is near the joint plane, as a result of strong convective mixin g and high incident flux, even though the melting temperatures are differen t. Strong mixing is confirmed by measured concentration profiles across acr oss the fusion zones of dissimilar metals. To a first approximation fusion zone depths with depth-to-width ratios greater than or identical to unity a re determined from scale analyses of heat conduction equations in welding t he same metals with a high and low-power-density beam, respectively. The pr opositions are verified by experimental results.