FeNiMnAl alloys show a wide range of microstructures and mechanical properties, but have been little explored.  Studies on four different types of microstructures in this alloy system will be outlined: 1) ultrafine microstructures (5-50 nm), present in Fe30Ni20Mn20Al30, Fe25Ni25Mn20Al30 and Fe35Ni15Mn25Al25, which consist of (Fe, Mn)-rich B2-ordered (ordered b.c.c.) and (Ni, Al)-rich L21-ordered (Heusler) phases, and in Fe30Ni20Mn25Al25, which consist of (Ni, Al)-rich B2 and (Fe, Mn)-rich b.c.c. phases, with the phases aligned along 100>; 2) fine microstructures (50-70 nm), present in Fe30Ni20Mn30Al20, Fe25Ni25Mn30Al20, and Fe28Ni18Mn33Al21, which consist of alternating (Fe, Mn)-rich f.c.c and (Ni, Al)-rich B2-ordered plates with an orientation relationship close to f.c.c.(002)//B2(002); f.c.c.(011)//B2(001); 3) coarser (0.5-1.5 µm) lamellar microstructures observed in alloys with a lower aluminum content, such as Fe30Ni20Mn35Al15, that consist of alternating (Fe, Mn)-rich f.c.c and (Ni, Al)-rich B2-ordered phases with a Kurdjumov-Sachs orientation relationship between the phases; and 4) carbon-doped, single-phase high-entropy Fe40.4Ni11.3Mn34.8Al7.5Cr6 alloys. The microstructures and mechanical properties in these alloys have been determined as a function of annealing time, testing temperature and strain rate.  Some of the unusual mechanical behavior that has been observed will be emphasized. Ian Baker obtained his B.A. and D. Phil. in Metallurgy and Science of Materials from the University of Oxford. He joined the Faculty of the Thayer School of Engineering at Dartmouth College, in 1982, where he is currently the Sherman Fairchild Professor of Engineering, Senior Associate Dean for Academic Affairs. He is a Chartered Engineer (U.K.) and a Fellow of ASM International, The Minerals, Metals and Materials Society, The Institute of Materials, Minerals and Mining (U.K.), the Materials Research Society, and the American Association for the Advancement of Science. Research interests include: mechanical behavior, including wear and fracture of metals, compound semiconductors, intermetallic compounds and ice; processing and recrystallization phenomena, particularly the effect of particles on recrystallization and processing by directional recrystallization; applications of electron microscopy, X-ray diffraction and X - ray topography, particularly in-situ deformation experiments; the structure, chemistry and properties of snow, firn and ice cores; production and properties of nanocrystalline, particularly magnetic, materials; nanoparticles for biomedical applications.