Disclosed are a low-cost ultra-high-strength multiphase steel plate/steel strip and its manufacturing method. Said steel plate/steel strip comprises the following components in percentage by weight: 0.03 to 0.07% of C, 0.1 to 0.5% of Si, 1.3 to 1.9% of Mn, less than or equal to 0.02% of P, less than or equal to 0.01% of S, 0.01 to 0.05% of Al, 0.2 to 0.5% of Cr, 0.07 to 0.14% of Ti, less than 0.03% of (Ni+Nb+Mo+V), and the balance being Fe and other inevitable impurities; and Mn+1.5Cr+5 (Ti+Al+Cu)+10(Mo+Ni)+20(Nb+V)<3.0; Mn+2Cr+4Ti+4Nb+4V+4MoSi/3+2C3.0. The steel plate is mainly used for the manufacturing of automotive chassis and suspension system parts.

An ultra-high strength steel (UHSS) includes a composition designed and processed such that the UHSS has properties comprising a tensile strength of about 2020 MPa, a yield strength of about 1781 MPa and a fracture toughness of about 105 MPa.Math.m.sup.1/2. The composition incudes Co no more than 8 wt % of the UHSS. The excellent mechanical performance of the UHSS is achieved by nanoscale -NiAl and M.sub.2C precipitates. The strength and toughness of the UHSS are comparable to those of the commercially used Aermet100 and M54 steels, while the cost of the UHSS is extremely low because of low NiCo concentration. This notable cost advantage makes the novel UHSS very competitive for potentially broad applications as structural components in the field of aerospace.

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.

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.