Jean M. Bennett,1
Shew M. Wong,3
and George Krauss2
1U.S. Naval Weapons Center, Physics Division, Michelson Laboratory, China Lake, California 93555
2Colorado School of Mines, Department of Metallurgical Engineering, Golden, Colorado 80401
3Rockwell International, Rocky Flats Plant, Golden, Colorado 80401 when this work was performed; he is now with Solar Energy Research Institute, Golden, Colorado 80401.
Jean M. Bennett, Shew M. Wong, and George Krauss, "Relation between the optical and metallurgical properties of polished molybdenum mirrors," Appl. Opt. 19, 3562-3584 (1980)
A study has been performed to determine the correlation among the microstructure, metallurgical processing, and optical surface finish of commercially available types of molybdenum (Mo) bar and plate and 0.5-mm thick Mo sheet. Specimens of bar and plate stock produced from low-carbon vacuum-arc-cast Mo or powder-metallurgy-processed Mo, as well as TZM (Ti-Zr-Mo) Mo alloy, were in the form of 3.86-cm diam disks. In addition, typical cross-rolled sheet specimens were produced from powder-metallurgy-processed Mo that had a very fine grain structure and a high degree of texture. Specimens were extensively characterized both optically and metallurgically. It was found that well-polished surfaces have surface topographies directly related to the microstructure and hence to the processing of the material. In sheet material having a well-developed texture, the polishability appeared to be independent of texture, and the grain size did not result in a lower scatter surface. It was concluded that the optimum type of Mo to use for smooth low-scatter mirrors is low-carbon vacuum-arc-cast plate or sheet material.
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Pancake–shaped grains as large as 180 um in width. Substructure within grains appears to correlate features on Nomarski micrograph.
Elongated grain structure ∥ mirror surface. Some inclusions on as–polished surface.
NCS9152
271.39 ±16.10
Polished and coated with (MgO/MgF2)7/Al
15.0
Unetchable, but circular particles visible. Diameter of particles 0.25 to 2.0 μm.
Elongated grain structure ⊥ mirror surface. Very uniform worked grain structure. Elongated inclusions and/or pores––correlate with powder metallurgy processing (see SEM micrographs).
NTZM10395
326.00 ±15.00
Polished and coated with (ZrO2/MgF2)4/Al
22.0
Unetchable. High hardness correlates with alloying.
Elongated grain structure ⊥ mirror surface. Carbide particles about 2.5 μm in diameter.
N243
261.33 ±12.77
Polished
14.0
Duplex grain structure. Finest grain structure correlate with surface features. Mixed grain sizes correlate with larger final bar diameter.
Pancake–shaped grains as large as 180 um in width. Substructure within grains appears to correlate features on Nomarski micrograph.
Elongated grain structure ∥ mirror surface. Some inclusions on as–polished surface.
NCS9152
271.39 ±16.10
Polished and coated with (MgO/MgF2)7/Al
15.0
Unetchable, but circular particles visible. Diameter of particles 0.25 to 2.0 μm.
Elongated grain structure ⊥ mirror surface. Very uniform worked grain structure. Elongated inclusions and/or pores––correlate with powder metallurgy processing (see SEM micrographs).
NTZM10395
326.00 ±15.00
Polished and coated with (ZrO2/MgF2)4/Al
22.0
Unetchable. High hardness correlates with alloying.
Elongated grain structure ⊥ mirror surface. Carbide particles about 2.5 μm in diameter.
N243
261.33 ±12.77
Polished
14.0
Duplex grain structure. Finest grain structure correlate with surface features. Mixed grain sizes correlate with larger final bar diameter.