Efficient Generation of Electricity

www.msm.cam.ac.uk/phase-trans

ThermodynamicsCannot win, can only break even

Cannot reach absolute zero

Can only break even at absolute zero

Goal

Increase as far as is possible, the maximum temperature in the cycle

i.e. better materials & engineering

Charpy

fatigue

oxidation, corrosion

tensile, creep

critical stress intensity

MULTIPASS ARC WELD

L.-E. SVENSSON

C, Mn, Si, Ni, Mo, Cr, V, Nb, Ti, Al,

N, O, P, S B, …..

Casting, forging …..

welding parameters and processes

prolonged heat treatments

cost

The Variables

thermodynamics

kinetics

cost models

microstructure

bayesian neural

networks

alloy design

oxidation

validation

processing

Nickel base alloy FT750dc

wt%

40 m

0

200

400

600

800

1000

0 200 400 600 800 1000 1200

Temperature / °C

Yie

ld s

tres

s /

MP

aTancret & Bhadeshia,

2002

FT750dc

0

100

200

300

400

500

600

700

1 2 3 4 5 6

log (t /h)

rup

ture

str

ess

/ M

Pa

Tancret & Bhadeshia,

2002

ferritic alloy C wt%

Cole & Bhadeshia,

2002

650 oC

Mechanically Alloyed

Oxide Dispersion Strengthened Metals

Fe-20Cr-5Al-0.5Ti-0.3 yttria

wt%

90% reduction

Capdevila & Bhadeshia, 2000

Capdevila & Bhadeshia, 2000

Helical grains

Capdevila & Bhadeshia, 2000

thermodynamics

kinetics

cost models

microstructure

bayesian neural

networks

alloy design

oxidation

validation

processing

Problems

• During the development of these models, we have discovered some fundamental difficulties with theory

• In particular, theory dealing with small driving forces

diaz del Castillo & Bhadeshia, 2001a

diaz del Castillo & Bhadeshia, 2001a

Conclusions

• There has been progress in predicting alloy behaviour

• Much more progress needed in theory

• Oxidation models?