METHOD FOR PROVIDING STRONG TOUGH METAL ALLOYS

摘要

A method for improving the strength and toughness of an austenitic metal alloy selected from the group consisting of stainless steal alloys of the AISI 200 and 300 series and non-stainless steel alloys containing iron, manganese, chromium, and carbon, said alloy having an Md temperature of no higher than about 100.degree.C and an Ms temperature of no higher than about minus 100.degree.C comprising the following steps: (a) deforming the alloy at a stain of at least about 10 percent and at a temperature in the range of about Md minus 50.degree.C to about Md plus 50.degree.C, said Md temperature being that of the alloy undergoing deformation, in such a manner that the material has a martensite phase of no greater than about 10 percent by volume and an austenite phase of at least about 90 percent by volume; and (b) deforming the material produced in step (a) at a strain of at least about 10 percent and at a temperature no higher than minus 75.degree.C in such a manner that the material has a martensite phase of at least about 50 percent by volume and an austenite phase of at least about 10 percent by volume; and an aged crystalline microstructure consisting essentially of a stainless steel alloy of the AISI 300 series having a martensite phase of at least about 50 percent by volume and an austenite phase of at least about 10 percent by volume and wherein the tensile strength of the alloy is at least about 190,000 pounds per square inch where the microstructure contains 50 percent martensite by volume and the tensile strength increases by at least about 2000 pounds per square inch for each additional percent of martensite above 50 percent.