MICROSTRUCTURAL FEATURES OF CRACKING IN AUTOGENOUS BERYLLIUM WELDMENTS

An investigation was conducted to determine the causes of centerline c racking in autogenous Be weldments. In agreement with earlier studies, features on the fracture surfaces consistent with hot shortness crack ing were observed. However, the present study reveals a more complicat ed solidification path than previously described. Analytical transmiss ion electron microscopy (TEM) studies of the weld centerline revealed low-melting constituents consisting of a MBe(12) grain boundary film a nd nodules containing elemental Al, elemental Si, and AlFeBe4 phases. Possible solidification pathways to produce this structure are discuss ed in terms of available binary and ternary phase diagrams.