During a CTE test, a stack of pure molybdenum samples (each 0.067 inch thick) was heated to 4000F. Melting of the material was noted in the center of the samples. Moly shouldn't melt until around 4700F. So I figured that there must be an alloy or some contamination of the base metal. We did the CTE test up to 3800F and got melting. We redid it up to 3500F and still had some melting, but much less. My reaction was that there must be some alloy of moly. So I checked the solidified nugget on the SEM/EDS and found only moly with a possible trace amount of silicon (hard to tell since the moly peak overwhelmed the energy level where silicon is present). No other trace elements. Mo-5.5%Si has a eutectic at 3750F. But this doesn't explain why we still got melting at 3500F. The temperature is measured by an optical pyrometer. The material cert papers state the material is 99.95% moly.
Any ideas on what might be causing the low melting point?
Thanks for any help.
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