Pressure also influences the (p, T) range over which the phases of alloy
systems may exist. The diagram illustrates this at three pressures P1,
P2, and P3, for the binary A-B alloy system that
forms the compound AB3.
the pressure increases from P1 to P3 the stability
of AB3 increases. At P1 the compound decomposes into
A + B as the temperature is increased through the lowest invariant reaction
temperature. At P2, the transformation at the higher invariant
reaction temperature is an incongruent melting to a liquid and solid B.
For the pressure P3, the reaction now becomes a congruent melting
with the liquid having the same composition as the solid from which it