Long-range ordering in β-Cu-Zn-Al:: Experimental and theoretical study

We present the order-disorder transition temperatures for bcc Cu-Zn-Al shape-memory alloys measured by means of calorimetric and resistometric techniques. The investigation includes the line of compositions Cu(0.76-x/2)-Zn(x)-Al(0.24-x/2) (0 <= x <= 0.48), i.e., the line with a constant conduction electron per atom ratio, e/a=1.48. Experimental results are confronted with Monte Carlo simulations based on the Blume-Emery-Griffiths Hamiltonian. A set of exchange energies in first and second neighbors is calculated, which allows in close agreement reproduction of the experimental phase diagram.