Abstract

Using a laser interferometric method described elsewhere,¹ we report on isothermal dimensional stability of the following materials: Invar, Super Invar, Kovar, molybdenum, TZM, elkonite, Al₂O3, Si₃N₄, SiC, copper, fused silica (quartz), TiAlV, Kovar/Kovar welds, and composite structures of Mo/SiC, Mo/Si₃N₄, and Mo/Invar. Measurements were made over a two-month period with samples maintained in vacuum near 60°C. Quartz and Super Invar were used for secondary length references; copper for a secondary thermal reference. Invar was found to elongate ~1 ppm/month, molybdenum varies with manufacturer as does Kovar, Kovar/Kovar spot welds and seam welds shrank ~1 ppm/month, molybdenum composite structures shrank ~1 ppm/month, TZM, TiAlV, Si₃N₄, Al₂O₃ and SiC were all stable to ~0.1 ppm/month.

© 1986 Optical Society of America