# US 12,601,024 B2 · Heterostructured antimicrobial stainless steel and method for synthesizing the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,601,024 B2 - Document ID: US12601024B2 - Status: Granted - Kind: B2 - Application number: 18/161,907 - Filed: 2023-01-31 - Published: 2024-08-01 - Granted: 2026-04-14 - Earliest claimed: 2023-01-31 - Assignees: City University of Hong Kong - Applicants: City University of Hong Kong - Inventors: Liliana Romero Reséndiz; Yuntian Theodore Zhu; Jacob Chih-Ching Huang; Tao Yang - Web page: https://patentgrep.com/patent/US12601024B2 ## CPC - C21D 8/00: Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) - C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62) - C21D 6/004: {containing Cr and Ni} - C21D 6/005: {containing Mn} - C21D 6/008: {containing Si} - C21D 6/02: Hardening by precipitation - C21D 8/0221: characterised by the working steps - C21D 8/0236: {Cold rolling} - C21D 8/0273: {Final recrystallisation annealing} - C21D 9/46: for sheet metals - C22C 38/001: {containing N} - C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60} - C22C 38/008: {containing tin} - C22C 38/02: containing silicon - C22C 38/04: containing manganese - C22C 38/06: containing aluminium - C22C 38/20: with copper - C22C 38/42: with copper - C22C 38/44: with molybdenum or tungsten - C22C 38/50: with titanium or zirconium - C22C 38/58: with more than 1.5% by weight of manganese - C22C 38/60: containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur - C21D 2211/001: Austenite - C21D 2211/008: Martensite - C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B) - C22C: ALLOYS (treatment of alloys C21D, C22F) ## Abstract A heterostructured antimicrobial stainless steel with improved yield strength and reduced strength-to-ductility trade-off and methods for synthesizing the same are provided. The heterostructured antimicrobial stainless steel has a plurality of mechanically strengthening mechanisms including: interstitial solid solution alloying elements; substitutional solid solution alloying elements; twins; multiphasic interfaces formed with face-centered cubic austenite phase and body-centered cubic martensite phase; statistically stored dislocations; strain-induced phase transformation; geometrically necessary dislocations pile-ups; stacking faults; precipitates; high density of grain boundaries; and HDI strengthening. ## Claims ### Claim 1 A method for synthesizing a heterostructured antimicrobial stainless steel with improved yield strength and reduced strength-to-ductility trade-off, having a heterostructured lamella structure arrangement formed with lamellar coarse grains surrounded by ultrafine grains; and a plurality of defects activating multiple strengthening mechanisms including: interstitial solid solution alloying elements; substitutional solid solution alloying elements; twins; multiphasic interfaces formed with face-centered cubic austenite phase and body-centered cubic martensite phase; statistically stored dislocations; strain-induced phase transformation, geometrically necessary dislocations pile-ups; stacking faults; precipitates; high density of grain boundaries, and hetero-deformation induced strengthening, the method comprising: a) casting a starting alloy with addition of antimicrobial element; b) subjecting the starting alloy to solid solution treatment to form a solid solution; c) quenching the solid solution to form a solid-solution treated stainless steel; d) subjecting the solid-solution treated stainless steel to aging to form an aged stainless steel; e) subjecting the aged stainless steel to cold rolling to form a cold-rolled stainless steel; f) subjecting the cold-rolled stainless steel to a final heat treatment to form the heterostructured antimicrobial stainless steel. ### Claim 2 (depends on 1) The method according to claim 1, wherein in step b), the solid solution treatment is performed at 1050° C. for a processing time in a range from 30 to 120 minutes. ### Claim 3 (depends on 1) The method according to claim 1, wherein in step d), the aging is performed at an aging temperature in a range from 550° C. to 700° C. for an aging time in a range from 30 to 360 minutes. ### Claim 4 (depends on 1) The method according to claim 1, wherein in step e), a thickness of the aged stainless steel is reduced for a range from 60% to 80% by cold rolling. ### Claim 5 (depends on 1) The method according to claim 1, wherein in step f), the final heat treatment is performed with a heating rate of 40° C. s−1. ### Claim 6 (depends on 5) The method according to claim 5, wherein in step f), the final heat treatment is a posterior aging treatment. ### Claim 7 (depends on 6) The method according to claim 6, wherein the posterior aging treatment is performed at an aging temperature in a range from 500 to 650° C. for an aging time in a range from 30 to 90 minutes. ### Claim 8 (depends on 1) The method according to claim 1, wherein in step f), the final heat treatment is an annealing treatment. ### Claim 9 (depends on 8) The method according to claim 8, wherein the annealing treatment is performed at an annealing temperature in a range from 700 to 800° C. for an annealing time in a range from 30 to 900 seconds. ### Claim 10 (depends on 1) The method according to claim 1, wherein the starting alloy has a nominal chemical composition of Cu in 0.01-0.08 wt. %, Ni in 3.00-14.00 wt. %, Cr in 7.00-20.00 wt. %, Mo≤3.00 wt. %, Mn≤2.00 wt. %, Si≤1.00 wt. %, balanced Fe, and addition of antimicrobial element ≤5.00 wt. %; and the antimicrobial element is Cu, Zn or Ag. ### Claim 11 A method for synthesizing a heterostructured antimicrobial stainless steel with improved yield strength and reduced strength-to-ductility trade-off, having a heterostructured lamella structure arrangement formed with lamellar coarse grains surrounded by ultrafine grains; and a plurality of defects activating multiple strengthening mechanisms including: interstitial solid solution alloying elements; substitutional solid solution alloying elements; twins; multiphasic interfaces formed with face-centered cubic austenite phase and body-centered cubic martensite phase; statistically stored dislocations; strain-induced phase transformation, geometrically necessary dislocations pile-ups; stacking faults; precipitates; high density of grain boundaries, and hetero-deformation induced strengthening, the method comprising: a) casting a starting alloy with addition of antimicrobial element; b) subjecting the starting alloy to solid solution treatment to form a solid solution; c) quenching the solid solution to form a solid-solution treated stainless steel; d) subjecting the solid-solution treated stainless steel to cold rolling to form a cold-rolled stainless steel; e) subjecting the cold-rolled stainless steel to a final heat treatment to form the heterostructured antimicrobial stainless steel. ### Claim 12 (depends on 11) The method according to claim 11, wherein in step b), the solid solution treatment is performed at 1050° C. for a processing time in a range from 30 to 120 minutes. ### Claim 13 (depends on 11) The method according to claim 11, wherein in step d), a thickness of the solid-solution treated stainless steel is reduced for a range from 60% to 80% by cold rolling. ### Claim 14 (depends on 11) The method according to claim 11, wherein in step e), the final heat treatment is performed under a heating rate of 40° C. s−1. ### Claim 15 (depends on 11) The method according to claim 11, wherein in step e), the final heat treatment is an aging treatment. ### Claim 16 (depends on 15) The method according to claim 15, wherein the aging treatment is performed at an aging temperature in a range from 500 to 650° C. for an aging time in a range from 30 to 90 minutes. ### Claim 17 (depends on 11) The method according to claim 11, wherein in step e), the final heat treatment is an annealing treatment. ### Claim 18 (depends on 17) The method according to claim 17, wherein the annealing treatment is performed at an annealing temperature in a range from 700 to 800° C. for an annealing time in a range from 30 to 900 seconds. ### Claim 19 (depends on 11) The method according to claim 11, wherein the starting alloy has a nominal chemical composition of Cu in 0.01-0.08 wt. %, Ni in 3.00-14.00 wt. %, Cr in 7.00-20.00 wt. %, Mo≤3.00 wt. %, Mn≤2.00 wt. %, Si≤1.00 wt. %, balanced Fe, and addition of antimicrobial element ≤5.00 wt. %; and the antimicrobial element is Cu, Zn or Ag.