New iron base alloys containing aluminum and boron are disclosed. The alloys are subjected to a rapid solidification processing (RSP) technique which produces cooling rates between .about.10.sup.5 to 10.sup.7 .degree. C./sec. The as-quenched ribbon or powder, etc consists primarily of a metastable crystalline solid solution phase. The metastable crystalline phases are subjected to suitable heat treatments so as to produce a transformation to a stable multiphase microstructure which includes borides. The heat treated alloy exhibits superior mechanical properties with good corrosion and oxidation resistance.