Materials for engineering, 3rd Edition - (Malestrom)

Structure of engineering materials 23
g
b
Liquid (L)
Temperature
T e
a′
a
α + L
α
α + β
g
%X
1.17 Formation of metastable eutectic by rapid solidification of alloy
of composition g–g.
T 2
L + α
L
T 1
Temperature
T p
α
a
e d b
α + β
L + β
β
g
f
A c l d c 2 B
%B
1.18 Phase diagram showing a peritectic reaction.
peritectic temperature and the boundaries of the β phase fd and gd are seen
to come to a point at this temperature.
An alloy of composition d is said to have the peritectic composition, and
we will now examine the nature of the phase change in more detail. Freezing
of alloy d will start at temperature T 1 by the separation of crystals of the α
solid solution; as the temperature falls under equilibrium conditions, the
composition of the solid solution will follow the line of the solidus to a and
that of the liquid will follow the line of the liquidus to b.