《Lecture 18-Titanium(Complete)》.pdf

Light Metals Lecture 18: Titanium MMAT 380 Topics to be covered • Production of Ti • Ti in context with other metals • Introduction to crystallography of Ti • 4 alloy groups – chemistry, – phase diagrams – heat treatments and microstructures – mechanical properties – applications 1 Production of Ti • Obtained from minerals: – rutile (TiO ) 2 – ilmenite (FeO-TiO ) approx 97-98% TiO 2 2 • Chemically converted to pure TiCl4 • Kroll Process: – TiCl4 reacted with liquid Mg at ~773-873°C in a closed stainless-steel vessel (retort) – 4TiCl4 (gas) + 2Mg (liquid) Ti (solid) + 2MgCl2 (liquid) Ti sponge Preparation of Ti Ingots • Molten Ti reacts with oxygen nitrogen • Ti sponge crushed compacted into electrode compacts – these welded together – form consumable electrode – for vacuum arc melting • For alloy ingots the alloying materials are mixed with the crushed Ti sponge before compacting 2 Production of Titanium Titanium Alloys • Relatively new engineering metals • Been in use as structural materials only since 1952 • Ti alloys attractive because: – High strength/weight ratio – High elevated temperature properties (i.e., ~550°C) – Excellent corrosion resistance (particularly in oxidizing acids and chloride media and in most natural environments) • Disadvantage is cost i.e., Ti ~6x cost of aluminum and 10x cost of stainless steel • However they do compete effectively in areas where strength/weight and high-elevated tem