Chapter 8.7

Chapter 8.7 - 9 “Superalloys”(Co Ni based solid solution hardening and secondary phases 33 MSE 2090 Introduction to Materials Science Chapter 8

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31 MSE 2090: Introduction to Materials Science Chapter 8, Failure Mechanisms of Creep Different mechanisms are responsible for creep in different materials and under different loading and temperature conditions. The mechanisms include ¾ Stress-assisted vacancy diffusion ¾ Grain boundary diffusion ¾ Grain boundary sliding ¾ Dislocation motion Different mechanisms result in different values of n, Q c . Grain boundary diffusion Dislocation glide and climb
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32 MSE 2090: Introduction to Materials Science Chapter 8, Failure Alloys for high-temperature use (turbines in jet engines, hypersonic airplanes, nuclear reactors, etc.) Creep is generally minimized in materials with: 9 High melting temperature 9 High elastic modulus 9 Large grain sizes (inhibits grain boundary sliding) Following alloys are especially resilient to creep: 9 Stainless steels 9 Refractory metals (containing elements of high melting point, like Nb, Mo, W, Ta)
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Unformatted text preview: 9 “Superalloys” (Co, Ni based: solid solution hardening and secondary phases) 33 MSE 2090: Introduction to Materials Science Chapter 8, Failure Summary ¾ Brittle fracture ¾ Corrosion fatigue ¾ Creep ¾ Ductile fracture ¾ Ductile-to-brittle transition ¾ Fatigue ¾ Fatigue life ¾ Fatigue limit ¾ Fatigue strength ¾ Impact energy ¾ Intergranular fracture ¾ Stress raiser ¾ Thermal fatigue ¾ Transgranular fracture Make sure you understand language and concepts: 34 MSE 2090: Introduction to Materials Science Chapter 8, Failure Reading for next class: Chapter 9: Phase diagrams ¾ Fundamental concepts and language ¾ Phases and microstructure ¾ Binary isomorphous systems (complete solid solubility) ¾ Binary eutectic systems (limited solid solubility) ¾ Binary systems with intermediate phases/compounds ¾ The iron-carbon system (steel and cast iron)...
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This note was uploaded on 02/14/2012 for the course MSE 2090 taught by Professor Leoindzhiglei during the Fall '10 term at UVA.

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Chapter 8.7 - 9 “Superalloys”(Co Ni based solid solution hardening and secondary phases 33 MSE 2090 Introduction to Materials Science Chapter 8

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