METEORIC AND ARTIFICIAL NICKEL-IRON ALLOYS. 
67 
Fig. 23. 
converse being true when the transition temperature is raised (cf. 6t and 6u, repre¬ 
senting the case in which the transition point is that of nickel raised by addition 
of iron). r 
The fundamental ideas represented in the diagram may be summarised as 
follows :— 
(1) When an alloy contains less than GB per cent, of nickel, the crystals which 
separate first contain less nickel than the remainder of the alloy, and are richer in 
iron the less the percentage amount of nickel in the material. 
(2) When GB per cent, of the nickel is present, crystals of two kinds, one relatively 
rich and the other relatively poor in nickel, can exist in equilibrium with the (non¬ 
magnetic) solution containing GB per cent, of Ni and separate simultaneously when 
the temperature corresponding to CfEF is reached. 
(3) When the percentage of nickel exceeds GB the crystals which first form on 
cooling are those of the second type, relatively rich in nickel. 
(la) The ultimate state, at the temperature represented by GEF, of an alloy 
containing less than GB per cent, of nickel is different according as the percentage of 
nickel present is less than or exceeds GE. 
If the alloy contains less than GE per cent, of Ni, it will be crystallised completely 
before GEF is reached, and will contain crystals of one type only, of which the 
percentage composition will be the same as that of the originally uncrystallised 
alloy. The alloy will be homogeneous at the temperature represented by GEF. 
If the alloy contains more than GE per cent, of nickel, the percentage of Ni in 
the crystals will increase, at the same time that the total amount increases, until the 
eutectic temperature is reached. Here the lasf of the solid solution (containing GB 
per cent, of Ni) crystallises, but partly in the form of crystals weak in nickel 
(containing GE per cent.) and partly in the form of crystals stronger in nickel 
k 2 
