metals and alloys Flashcards
What are metals at ambient temperature?
hard and lustrous
closely packed crystalline sturctures
opaque
conductors of heat and electricity
What is an alloy?
mixture of 2 or more metals
what is a binary alloy?
mixture of 2 metals
what is a ternary alloy?
mixture of 3 metals
What is an alloy system?
all possible combinations of an alloy
in molten state, what do metals display?
mutual solubility
What structure are metals?
regular crsytaline structure
What are metals composed of?
many small crystals called grains
what is a grain boundary?
where crystals abut their neighbour
when do grains stop growing?
when all melt metal consumed
what is heterogeneous nucleation?
many sites of nucleation
majority of dental application
what is homogeneous nucleation?
single site of nucleation
requires specialist equipment
metal so pure it requires 4 metal atoms to come together
how does grain size influence metals?
can influence physical properties
What techniques promote small grain size?
rapid solidification- lost wax technique
provision of extra nucleation sites- irradium
what factors affect grain size?
temperature of mould
shape of mould
What size of grain does slow cooling produce?
large grain
what size of grain does rapid cooling produce?
small grains
how can grain boundaries be visualised?
light reflecting microscope
polished metal surface
application of etching chemical
what is malleability?
the degree of compression in response to an applied compressive force
what are the three types of solid solutions that can be formed?
ordered solid- component metals have specific sites in common lattice
random solid- random sites in solid crystal lattice
interstitial solid- stoms of one lie in primary lattice sites of other
compared with pure metals what are solid solutions?
harder
stronger
