Accession Number : ADA318433

Title :   Hierarchical Adaptive Microstructures: Smart Steels.

Descriptive Note : Final rept. 1 Sep 93-29 Aug 96,

Corporate Author : NORTHWESTERN UNIV EVANSTON IL

Personal Author(s) : Olson, Gregory B.

PDF Url : ADA318433

Report Date : OCT 1996

Pagination or Media Count : 50

Abstract : Inspired by biomimetic concepts, a systems approach to materials design is extended to hierarchical adaptive microstructures undergoing a programmed dynamic evolution in both processing and service to achieve novel combinations of properties. Fundamental principles are developed to support rational design of (a) high-toughness ultrahigh-strength martensitic steels of interest for advanced armor and high performance gear applications, and (b) 'smart composite' ferrous superalloys for damage tolerant high temperature applications in advanced tank propulsion systems. Theoretical modelling and high resolution microanalytical experiments in the martensitic alloys address control of autocatalytic coherent precipitation to achieve efficient strengthening without embrittlement, and the controlled precipitation of optimal stability metastable austenite for adaptive dilatant transformation plasticity tuned to crack-tip stress states for efficient interaction with strain localization processes in ductile fracture. Novel composite strategies address thermodynamically compatible shape-memory alloy reinforcement for pseudoelastic crack-bridge toughening of high temperature superalloys, combined with self-healing of low temperature damage by shape-memory-assisted crack rewelding at service temperatures.

Descriptors :   *MICROSTRUCTURE, *STEEL, *ADAPTIVE SYSTEMS, *HIERARCHIES, CONTROL, ARMOR, LOW TEMPERATURE, STABILITY, OPTIMIZATION, STRATEGY, DAMAGE, INTERACTIONS, DYNAMICS, MATERIALS, HIGH TEMPERATURE, COMPUTER PROGRAMMING, EMBRITTLEMENT, ALLOYS, HIGH RESOLUTION, STRENGTH(MECHANICS), FRACTURE(MECHANICS), AUSTENITE, PROPULSION SYSTEMS, PRECIPITATION, PLASTIC PROPERTIES, SYSTEMS APPROACH, IRON ALLOYS, DUCTILITY, GEARS, METASTABLE STATE, TRANSFORMATIONS, SUPERALLOYS, MARTENSITE, MICROANALYSIS.

Subject Categories : Properties of Metals and Alloys
      Inorganic Chemistry
      Atomic and Molecular Physics and Spectroscopy
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE