Ductility Enhancement of Molybdenum Phase by Nano-sizedd Oxide Dispersions

Bruce Kang

关键词: ALLOY SYSTEMS;    ALLOYS;    BEHAVIOR;    BONDING;    CHARGES;    CHEMICAL BONDS;    CHROMIUM;    COMPUTERS;    DATES;    DISPERSIONS;    DUCTILITY;    ELECTRONIC STRUCTURE;    ELECTRONS;    EVALUATION;    IMPURITIES;    INCLUSIONS;    LEAD;    MAGNESIUM OXIDES;    MATERIALS;    MECHANICAL PROPERTIES;    METALS;    MOLYBDENUM;    NITROGEN;    OPTIMIZATION;    OXIDES;    PARTICLES;    PERFORMANCE;    POPULATIONS;    PROCESSING;    SIMULATION;    SIZE;    SYNTHESIS;    TESTING;    VALENCE;   

DOI  :  10.2172/952943
RP-ID  :  None
PID  :  OSTI ID: 952943
Others  :  TRN: US201002%%1512

学科分类：材料科学（综合）

美国|英语

来源: SciTech Connect

【 摘 要 】

The present research is focused on ductility enhancement of molybdenum (Mo) alloys by adding nano-sized oxide particles to the alloy system. The research approach includes: (1) determination of microscopic mechanisms responsible for the macroscopic ductility enhancement effects through atomistic modeling of the metal-ceramic interface; (2) subsequent computer simulation-aided optimization of composition and nanoparticle size of the dispersion for improved performance; (3) synthesis and characterization of nanoparticle dispersion following the guidance from atomistic computational modeling analyses (e.g., by processing a small sample of Mo alloy for evaluation); and (4) experimental testing of the mechanical properties to determine optimal ductility enhancement.Through atomistic modeling and electronic structure analysis using full-potential linearized muffin-tin orbital (FP-LMTO) techniques, research to date has been performed on a number of selected chromium (Cr) systems containing nitrogen (N) and/or magnesium oxide (MgO) impurities. The emphasis has been on determining the properties of the valence electrons and the characteristics of the chemical bonds they formed. It was found that the brittle/ductile behavior of this transitional metal system is controlled by the relative population of valence charges: bonds formed by s valence electrons yield metallic, ductile behavior, whereas bonds formed by d valence electrons lead to covalent, brittle behavior. The presence of valence bands from impurities also affects the metal bonding, thereby explaining the detrimental and beneficial effects induced by the inclusion of N impurities and MgO dispersions. These understandings are useful for optimizing ductility enhancement effects on the dispersion materials.