Constitution and Magnetic Properties of Ni75MnxAl25 - x-Alloys (0 less than equivalent to multiplied by less than equivalent to 25). Part 2. Ferromagnetic Properties and Ordering Behaviour.

The saturation magnetization sigma //s and the ferromagnetic Curie temperature T//f of Ni//7//5Mn//xAl//2//5// minus //x alloys increases from that of the intermetallic compound Ni//3Al with increasing Mn concentration and reaches a maximum value at the Ni//3Mn phase. Of the samples quenched from liquid or high temperatures, the alloy with 12. 5 at. Percent Mn possesses the maximum sigma //s value. In Ni//7//5Mn//xAl//2//5// minus //x alloys, the maximum value of sigma //s is closely related to the formation of the Ni//3Mn phase and hence is largely determined by the annealing method used. It could be shown that in each of the examined Ni-Mn-Al alloys, there exists a critical annealing temperature T//k at which maximum ordering takes place. The critical annealing temperature T//k decreases with increasing Mn concentration. The observed values for the Ni//3Mn phase are as follows: T//k equals 693 K (420 degree C), sigma //s equals 100. 2 Gcm**3 g** minus **1 ( AM**2 kg** minus **1) and T//f equals 763 K (490 degree C).