Material science
1) Polypropylene (PP) has a glass-transition temperature of -15 oC
and a melting temperature of 175 oC. This means that at a
temperature of -40 oC that PP is ________, and at temperature
0 oC PP is _________ .
(A) brittle, brittle (B) ductile, brittle (C) brittle, ductile
(D) ductile, ductile (E) low in thermal conductivity, high
in thermal conductivity.
.2) Galvanized steel corrodes slowly in air because:
(A) the Sn coating completely covers the steel.
(B) the Zn coating completely covers the steel.
(C) the Zn corrodes rather than the steel.
(D) the Sn corrodes rather than the steel.
(E) the Fe has an adherent oxide layer. ______________
3) Stopping the motion of which imperfection in metals results in
strengthening the metal (at low temperature): (A) vacancies
(B) grain boundaries (C) inclusions (D) dislocations
(E) interstitials? ______________
4) Which process for a plain carbon steel (1080) results in coarse
pearlite:
(A) anneal (B) austemper (C) normalize
(D) interrupted quench (E) quench and temper.
1) option c)brittle, ductile
below tg (glass transition temperature)material will be brittle. so at -40 c(temperature<tg) it will be brittle.
oc is above tg,so it will be a glossy ductile polymer at this temperature.so option c is answr
2)option c.
while galvanization iron is coated with zn. here steel is diffusion coupled with iron.corrosion is a diffusion controlled process.in diffusion coupling zn act as anode(more active metal) and steel act as cathod.the anode is corroded at accelerated rate while cathod is protected.so Zn corrodes rather than the steel
3)option d.
hindering the motion of dislocations in metals results in strengthening the metal (at low temperature)
4)option a
slower cooling of anneeling of plain carbon steel (1080) results in higher temperature transformation to in coarse pearlite:
Material science 1) Polypropylene (PP) has a glass-transition temperature of -15 oC and a melting...