Property and Cost Optimisation of Novel UHS Stainless Steels via a Genetic Alloy Design Approach

概要

論文の詳細を見る
A computational alloy design approach for precipitation harden Ultra High Strength (UHS) stainless steels is presented. The design methodology is based on thermodynamic and kinetic principles, employing genetic algorithm for optimization. Alloy compositions covering 14 elements are optimized simultaneously together with key heat treatment parameters, i.e., austenitization temperature and ageing temperature, so as to achieve the desired microstructures: strong lath martensite matrix, fine precipitates of particular species for strengthening, adequate Cr concentration in the matrix for corrosion resistance and controlled amounts of undesirable phases throughout the entire heat treatment. Two alloys utilizing MC carbides and Ni3Ti intermetallics, respectively, are designed employing the genetic approach. For the alloys designed, the cost effects of each single element are investigated and both the most and the least cost effective elements are identified. Subsequently the alloy design model was extended to take into account alloying costs by employing the ratio of strengthening contribution to alloying costs as the new optimization factor. Redesigned alloys display significant cost reductions without significantly sacrificing the strength. The extended model is shown to provide valuable guidelines in the industrial practice to design/modify alloy compositions, and optimize strength and cost in an integrated manner.