Transcript Slide 1

Mech 473 Lectures
Professor Rodney Herring
Molybdenum Alloys
In contrast to the other bcc refractory metals –
molybdenum is a relatively abundant material in the
Earth’s crust – and reasonable quantities of fine grained
material can be prepared by consumable electrode
melting – or by powder metallurgy followed by sintering.
Molybdenum Alloys
Mo and W form a continuous series of solid solutions and
the resultant solution strengthening increases the
degree of strain hardening that can be obtained by cold
work
Ti and Zr are added to form a fine dispersion of carbides in
order to restrict the recrystallization of Mo – so that
strain hardening can be retained to higher temperatures
Mo-5Re and Mo-41Re alloys have been developed for
improved high-temperature strength but such alloys are
not regarded as cost effective at the present time – as Re
is a relatively scarce and expensive metal
Microstructure of Mo Alloys
Fine grained structure of Mo prepared by powder
metallurgy and sintering
Effect of Temperature on UTS of Mo Alloys
As the basis of dispersive strengthening is the retention of
cold work – the advantages of dispersive phase alloying
disappear above the recrystallization temperature of
1000-1300 oC – when pure Mo is just as strong
Key
1 = TZM cold worked
2 = Pure Mo cold worked
3 = TZM recrystallized
4 = Pure Mo recrystallized
The End
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