The disk bend test has been a valuable technique for rapid evaluation of the ductility of a large number of alloys under consideration for use as structural materials in the breeder and fusion reactor programs. The test employs the 3-mm-diameter, 0.3-mm-thick microscopy and density disk specimen, conserving valuable experimental volume in the limited reactor space available.

The test involves bending the disk symmetrically about the center, producing a simple, axisymmetric stress state. Experimental results are in agreement with a theoretical analysis of the bend configuration. The advantages and limitations of the technique are discussed.

The test has shown that commercial precipitation-strengthened alloys and the Path B alloys of the U.S. Fusion Program exhibit unacceptably low ductilities following irradiation. This was demonstrated for a number of alloys, in a variety of thermomechanical conditions, including cold worked, cold worked and aged, and solution treated and aged.