Concise Dictionary of Materials Science Part 1 pdf

α-Fe Allotropic form of iron having BCC crystal structure and existing at tem-peratures below 910°C at atmospheric pressure.. α isomorphous Ti system Ti–X alloy system in which the allo

Structure and Characterization

of Polycrystalline Materials

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α-Al 2 O 3 Pure alumina Polycrystalline Al2O3 is known as corundum and single

crystals as sapphire Its crystal structure can be described as consisting

of two sublattices: an FCC sublattice of O2– ions and a sublattice of Al3+

ions occupying two thirds of the octahedral sites in the first one.

α-Fe Allotropic form of iron having BCC crystal structure and existing at

tem-peratures below 910°C at atmospheric pressure

α isomorphous Ti system Ti–X alloy system in which the alloying element X

is the α-stabilizer, i.e., it raises the temperature of the β↔ α polymorphic transformation.

α-phase [in Ti alloys] A solid solution of alloying elements in α-Ti

α′-martensite See titanium martensite

α″-martensite See titanium martensite

α-stabilizer In physical metallurgy of Ti alloys, an alloying element increasing

the thermodynamic stability of α-phase and thereby raising the β/(α+β)

transus in the corresponding phase diagram In physical metallurgy of steels, it is referred to as ferrite-stabilizer.

α-Ti Allotropic form of titanium having a hexagonal crystal structure and

exist-ing at temperatures below 882°C at atmospheric pressure The axial ratio

of its lattice c/a = 1.58, i.e., a little smaller than in an ideal HCP structure.

α Ti alloy Titanium alloy in which α-phase is the only phase constituent after air-cooling from the β-field in the phase diagram concerned Alloys with

a small fraction of β-phase (∼5 vol%) are usually related to the same group and are called near-α alloys All the α alloys contain α-stabilizers.

(α + β) brass Brass with two phase constituents: a copper-based substitutional

solid solution (α-phase) and an electron compound (β-phase)

(α + β) Ti alloy Alloy whose phase constituents are α- and β-phases after

air-cooling from the (α + β)-field in the phase diagram concerned Slow

cooling of these alloys from the β-field results in a microstructure com-prising grain-boundary allotriomorphs of the α-phase (known as “pri-mary” α) and packets of similarly oriented α-platelets with the β-phase layers between the platelets

A 1 /Ae 1 temperature In the Fe–Fe3C diagram, the temperature of an eutectoid

reaction corresponding to the PSK line in the diagram Since the reaction,

on cooling, starts at a certain undercooling ( see nucleation), the