Patent ID: 8409367

Claim:
A method of producing a steel sheet including a nanostructured austenite phase, the method comprising: treating a steel sheet including an austenite phase by surface mechanical attrition treatment and producing a strain-induced phase transformation of at least some of the austenite phase in the steel sheet to a martensite phase; after the strain-induced phase transformation, heating the steel sheet to a temperature in a range from 300° C. to 0.5T, where T is the melting point of the steel sheet; while the steel sheet is at an elevated temperature from the heating, rolling and deforming the steel sheet and producing a phase transformation of at least some the martensite phase in the steel sheet, at surfaces of the steel sheet, to a nanocrystalline austenite phase having a mean grain size less than 100 nm; and cooling the steel sheet to room temperature