Alloys, of iron, cobalt, nickel and chromium containing both metalloids and refractory metals are disclosed. The alloys are rapidly solidified at cooling rates of 10.sup.5 -10.sup.7 .degree. C./sec so as to produce an ultrafine grained metastable crystal structure having enhanced compositional homogeneity. The as-quenched metastable alloys are brittle, permitting pulverization, if desired. Heat treatment is used to convert the metastable brittle alloys into ductile alloys with primary grains of ultrafine grain size which contain an ultrafine dispersion of boride as well as carbide and/or silicide particles. The powders or ribbons can be consolidated into bulk parts. The heat treated alloys possess good mechanical properties, in particular high strength and hardness, as well as good corrosion resistance for selected compositions, making them suitable for many engineering applications.