Engineering Alloys (307) Lecture 3 Ni-Base Superalloys II ...
Engineering Alloys (307) Lecture 7 Titanium Alloys I David Dye Department of Materials, Imperial College Royal School of Mines, Prince Consort Road, London SW7 2BP, UK +44 (207) 594-6811, [email protected] Imperial College London Outline Page 2 Imperial College London
Ti primary production CP Ti and applications -Ti alloying, alloy designTi alloying, alloy design near-Ti alloying, alloy design alloy microstructures, forging and heat treatment / alloys, Ti-Ti alloying, alloy design6Al-Ti alloying, alloy design4V defects Ti Primary Production Kroll Process Page 3 Imperial College London Ti common in Earths crust
Energy to separate ~125 MWhr/tonne (4/kg just in power) Batch process over 5 days: Produce TiCl4 from TiO2 and Cl2 TiCl4 + 2 Mg 2 MgCl2 + Ti chip out Ti sponge (5-Ti alloying, alloy design8t) from reactor cost 5/kg Chlorides corrosive, nasty World annual capacity ~100,000 t, demand ~60,000t ($500m -Ti alloying, alloy design small) Need a cheaper process that is direct FFC (Cambridge) and others Subsequent Processing
Page 4 Imperial College London harvey fig p11 Casting Page 5 Imperial College London Use skull melting (EBHCR) instead of VIM/VAR/ESR for final melting stage in triple melting process Ti Allotropes, Phase Diagram Page 6 Imperial College London
Pure Ti: L (bcc) @ 1660 C (hcp) @ 883 C =4.7 g/cc highly protective TiO2 film Diffusion in 100x slower than in origin of better creep resistance
Alloying: Pure alloys Page 7 Imperial College London stabilisers: O, Al (N,C) stabilisers: V,Mo,Nb,Si,Fe neutral: Sn, Zr Strengthen pure alloys by
solid solution O, Al, Sn Hall-Ti alloying, alloy designPetch = 231 + 10.5 d cold work martensite reaction exists, of little benefit (not heat-Ti alloying, alloy designtreatable) Uses: chiefly corrosion resistance chemical plant heat exchangers cladding harvey fig p13 Table of CP Ti
Microstructures near alloys Page 8 Imperial College London stabilisers raise / transus stabilisers to widen / field and allow hot working heat treatable ~10% primary (grain boundary) during h.t. @ >900C oil quench intragranular plates + retained
age at ~625C to form , spheroidise and stress relieve Then >>90% Lightly deformed (~5%) Ti-834 Properties near- alloys Page 9 Imperial College London Refined grain size stronger better fatigue resistance
Predominantly few good slip systems good creep resistance Si segregates to dislocation cores inhibit glide/climb further Ti Creep Rates Page 10 Imperial College London + alloys: Microstructures Page 11 Imperial College London
Contain significant stabilisers to enable to be retained to RT Classic Ti alloy: Ti-Ti alloying, alloy design6Al-Ti alloying, alloy design4V >50% of all Ti used Classically 1065 C all forge @ 955C acicular on grain boundaries to inhibit coarsening Air cool produce lamellae colonies formed in prior grains (minimise strain), w/ in between (think pearlite)
Ti-6-4: heat treat Page 12 Imperial College London Ti-6-4: properties Page 13 Imperial College London N.B. Must avoid Ti3Al formation via Al equivalent: Al+0.33 Sn + 0.16 Zr + 10 (O+C+2N) < 9 wt% ppt hardening + grain size
Defects Page 14 Imperial College London Major -Ti alloying, alloy designrelated problem is the production of -Ti alloying, alloy designrich regions due to oxygen (+N) embrittlement the entrapment of O-Ti alloying, alloy designrich particles during melting Called case Also a problem in welding often Ti is welded in an Ar-Ti alloying, alloy designfilled cavity to avoid this
alloys suffer from -Ti alloying, alloy designrich regions from solute segregation ( flecks), and/or from embrittling phase, a diffusionless way to transform from -Ti alloying, alloy designbcc to a hexagonal phase. more in lecture on alloys Review: Titanium I (L7) Page 15 Imperial College London near-Ti Alloys microstructure / microstructure Casting
AP Melodic Dictation. There are two melodic dictation questions on the AP test. One will be in treble clef and one will be in bass clef. One will be in simple meter and one will be in compound meter. One...
Managing the LMB requires dealing with uncertainty and shifting values in an inclusive and comprehensive manner - this is not a trivial undertaking. Flexibility and nimbleness will be critical for the Member Countries in managing uncertainty and associated risk. SEI:...
Shanghai, China - one of the world's largest cities, busiest port, & financial center of the Pacific Rim Mumbai - India's largest city (15 million+) has a central role in country's banking, manufacturing, and Internet -related economies Challenges to economic...
5. Patients with successful weaning from CPB but requiring a significant amount of: Vasopressors (norepinephrine > 4 µg.min-1 or epinephrine > 2 µg.min-1). Inotropic drugs (dobutamine > 2 µg.kg-1.min-1 or the use of amrinone and milrinone) during the first 12...