Abstract: .epsilon. phase precipitates in the matrix having a composition of 0.07% or less carbon, 1 or less silicon, 1% or less manganese, 2.5 to 5% copper, 3 to 5.5% nickel, 14 to 17.5% chromium, 0.5% or less molybdenum, 0.15 to 0.45% niobium, by weight, and the balance composed substantially of iron, and comprising 6 to 30 vol % austenitic phase and the balance composed substantially of martensitic phase. In a method of producing a structural member in which first solution treatment is performed at 1010.degree. to 1050.degree. C. on a stainless steel having a composition described above and first aging treatment is performed at a temperature not lower than 520.degree. C. and not higher than 630.degree. C., second solution treatment is performed at 730.degree. to 840.degree. C., and then second aging treatment is performed at a temperature not lower than 520.degree. C. and not higher than 630.degree. C. or a structural member of any shape is fabricated by means of welding work before the second solution treatment.

Abstract: An alloy containing Mn in an amount of from 5 to 30 weight percent, at least one member selected from the group consisting of Sn of an amount of not more than 5 weight percent, Al of an amount of not more than 8.5 weight percent, Zn of an amount of not more than 7 weight percent, Fe of an amount of not more than 2.5 weight percent, and Ni of an amount of not more than 2.5 weight percent, and the balance to make up 100 weight percent of Cu plus normally entrained impurities produces a metallic material proof against the attachment thereto of marine organisms when the alloy fulfils a requirement that it should possess an .alpha.(face-centered cubic lattice) single-phase structure.