Metals and Alloys Flashcards
What is a metal?
an element whose atoms readily lose electrons to form positively charged ions
What is an alloy?
a crystalline solid with metallic properties that is composed of 2 or more chemical elements in which one is a metal and all are mutually soluble in molten state
What is the term for metals crystalising?
nucleation
An alloy with many sites of nucleation is?
heterogenous
An alloy with a single site of nucleation is?
homogenous
What are grains in alloys?
crystals
When do grains stop growing?
when metal has solidified
What do grains give rise to during growth?
boundaries between crystals where they impinge on each other
What does a finer grain size result in?
more nucleation sites
What alloys contain iridium?
gold alloys
What does iridium allow for?
many sites for nucleation
What does iridium act as?
grain-refining ingredient
What are 4 techniques for shaping alloys?
- hammering
- rolling
- pressing
- drawing through die (wire)
What are the 3 patterns of metals in alloys?
- ordered
- random
- interstitial
What is an intermetallic compound?
definite proportions of 2 or more elemental metals
What is the purpose of phase diagrams?
predict solid and liquid solutions
What is a binary alloy?
an alloy composed of 2 elements
In a phase diagram, what does a bigger distance between the lines mean?
greater coring - more erosion/ susceptibility to corrosion
What is a eutectic alloy?
alloy components are insoluble in each other so crystallisation occurs at a certain temperature
What are eutectic alloys used for?
soldering - attaching to an appliance to create a contact point
What is the point where the liquidous and solidus meet?
eutectic point
