Zay Jeffries (April 22, 1888 – May 21, 1965) was an American mining engineer, metallurgist, consulting engineer and recipient of the 1946 John Fritz Medal.
Jeffries was born in Willow Lake, South Dakota as one of the nine children of Johnston Jeffries and Florence (Sutton) Jeffries. He obtained his BSc in mining engineering at the South Dakota School of Mines and Technology in 1911. Three years later he also obtained his MSc in metallurgical engineering from the same school, and in 1918 Harvard University awarded him his Doctor of Science degree..
After his graduation in 1911 he had started as assayer for the Custer Co. mining company in South Dakota, yet later that year he accepted an appointment as instructor at Case Western Reserve University in Cleveland. In 1916 he was promoted to appointed assistant. In 1914 he also started as consulting engineer in the Cleveland-area. Later he consulted metallurgy Laboratories at the University of Chicago, and participated in the Manhattan Project.
Jeffries was elected member of the National Academy of Sciences in 1939. In 1946 he was awarded the John Fritz Medal.
- Jeffries, Zay, and Robert Samuel Archer. The science of metals. McGraw-Hill, 1924.
- Edwards, Junius David, Francis Cowles Frary, and Zay Jeffries. The aluminum industry. Vol. 1. McGraw-Hill book company, inc., 1930.
- Edwards, Junius David, Francis Cowles Frary, and Zay Jeffries. The Aluminum Industry: Aluminum products and their fabrication. Vol. 2. McGraw-Hill book company, Incorporated, 1930.
- Articles, a selection
- Jeffries, Zay. "Effect of temperature, deformation, and grain size on the mechanical properties of metals." Trans. AIME 60 (1919): 474-576.
- Jeffries, Zay, and R. S. Archer. "The slip interference theory of the hardening of metals." Chem. and Met. Eng 24.24 (1921): 1057.
- Jeffries, Zay. "The trend in the science of metals."Transactions of the American Institute of Mining and Metallurgical Engineers, 70 (1924): 303-327.