Robert,
Without looking at picture or xsection it is difficult to speculate.
Your description that ball has deformed may be pointing to what is
called 'Thermal Ratcheting' which is a failure mechanism observed when
there is plastic deformation during heating and cooling part of the
process. See Figure 6.58 (b) and (c) on page 211 of Failure modes and
mechanisms and compare to your case.

pratap

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