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PM Moataz - Titanium 1 - Coggle Diagram
PM Moataz - Titanium 1
Describe extraction and primary processing stages
Extraction
Clorination: Ti ore --> TiCl4 using chlorine gas, TiO2 and Carbon
Fractional Distillation: to purify
Reduction:
Kroll Process
where TiCl4 is heated to 850C with Mg to form Ti + MgCl2. Expensive and use large quantities of Mg
Removal of by-products: Removal of MgCl2 by acid leaching, inert gas sweep or vacuum distillation
Crushing and sizing: Ti sponge is crushed and sized
Processing
Vacuum arc remelting: Titanium electrode is made from sponge and scrap in inert chamber and then melted in an VAR furnace with the ingot forming below as the metal drips down.
New methods
Processing: Electron beam cold hearth metling uses a water cooled copper heath to ensure a thin layer of solid titanium is alwasy present and that the molten titanium only comes into contact with this. The top layer is melted with an electron beam and travels to an ingot pool for casting
Removes HDI and LDI defects
Extraction: electro-deoxidation process electrolytically separating titanium ions from oxygen to produce a sponge
Doesn't produce enough
Defects
Melt related defects
Low density inclusions (Al or Interstitial stabilised), High density inclusions (Tungsten, Tungsten carbide or other refractory metals/carbides
Casting defects
Shell reactions, face coat flaking, voids and shrinkage, tears
Thermo-mechanical Processing
Cracks and laps, Anoalous structures, SIP
Surface defects
Alpha case, cracking, tool tip enbedding
Explain influence of alloying elements
Ti exists in two phases, beta (HT) and alpha (LT).
Mo, V, Nb stablise beta
AL, Sn, Zr stabilise alpha
Classification of alloys
Lutjering's
Alpha, alpha+beta, metastable and stable beta
Donachie's
CP, alpha, near alpha, alpha+beta, near beta and beta
Properties
Beta has:
:arrow_up: density
:arrow_up: short-time strength
:arrow_up: strain rate sensitivity
:arrow_up: fabricability
Alpha has:
:arrow_up: creep strength
:arrow_up: weldability
Beta decomposition
BCC Beta :arrow_right: hexagonal alpha
Martensitically (rapid quench)
5 Different compositions:
\(\alpha'\)
\(\alpha''\)
\(\alpha' + \beta + \omega\)
\(\beta + \omega\)
retained \( \beta\)
\(\alpha'\) forms with fast cooling and low \(\beta\) stabilisers present via
diffusionless transformation
forming laths packets or acicular morphologies.
\(\alpha''\) forms in more
solute rich
alloys due to supersaturation and
distortion
of the hexagonal structure
\(\beta + \omega \) forms when \(\beta\) stabilised alloys are rapidly cooled. Further aging causes \(\omega\) to change from athermal to isothermal. Acts as nucleation site for \(\alpha\)
Diffusion controlled nucleation
Other phases
\(\beta\) :arrow_right: \(\beta + \beta'\) occurs in high concentrations of \(\beta\) stabilised when alloying elements segragate to the grain boundaries
\(\alpha 2\) precipitation are fine particles that form when long aging
Methods of classifying alloys
CP/\(\alpha\)
Unalloyed titanium with limited amounts of Fe and interstitial elements
Properties: :check:corrosion resistance, :check: fabricability and weldability, :check: toughness
Uses: Chemical/petrochemical, processing equipment, heat exchangers
Near \(\alpha\)
Contain Al, Sn and Zr to stabilise \(\alpha\)
Properties: :check: High temperature, :check: Yield stress, :check: Creep resistance in lamellar microstructures, :check: Fatigue strength at high temp
Uses: High pressure compressor disks and blades in aeroengines (max temp ~480)
Microstructure: Low \(\beta\), strengthened by Ti-Si precipitates
Plain sections are alpha
\(\alpha + \beta\)
Good mechanical properties and easy manufactured, but dependent on microstructure (max temp ~400)
Properties: :check: Yield strength, :check: Ductility, :check: fatigue properties, :check: toughness, :check: prosessability
Uses: structural aerospace, Compressor and fan blades in engines, oil and gas drilling, sports equipment
Near \(\beta\)
Higher levels of \(\beta\) stabilisers, can be heat treated to form a very fine \(\alpha\) phase
Properties: :check: yield strength, :check: fatigue strength, :check: ductility, :check: easier to forge, :check: low stiffness
Uses: Large structural forgings, precision and high strength forging, springs, biomedical applications
Microstructure: Very fine \(\alpha\) particles in a \(\beta\) matrix, varying amounts of primary \(\alpha \), grain boundary \(\alpha\)
