Alkali halides and alkaline earth fluorides have many attractive optical properties which are of interest for component applications in several optical systems operating in adverse environments. The fact that many of these materials have low yield strengths and fracture energies in single-crystal form often restricts their applications. The yield strengths and fracture energies of single crystals of many alkali halides can be increased significantly, in many cases by an order of magnitude or more, by deformation processing, such as press forging. The slow compressive deformation and high temperatures to which materials are subjected during press forging introduce low- and high-angle grain boundaries which are responsible for the observed improvement in mechanical properties. This paper describes a forging technique which repeatedly produces crack-free, fine-grained forgings and discusses the optical and mechanical properties of press forged LiF and CaF2 in relation to those of starting single crystals.
R. H. Anderson,
R. A. Skogman,
"Mechanical And Optical Properties Of Press-Forged LiF and CaF2," Optical Engineering 18(6), 186602 (1 December 1979). https://doi.org/10.1117/12.7972441