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In this study, Nd and As are mainly sealed into industrial pure Fe cylinders. The effect of different temperatures on the high-temperature interaction of an Nd–Fe–As ternary system is studied via X-ray diffraction, optical microscopy, and scanning electron microscopy after heat insulation for 30 h at 1173, 1223, and 1273 K. The results show that the common products under high-temperature interaction are NdAs, Fe17Nd2, and Fe. Fe12As5 is present at 1173 K, whereas Fe2As is produced at 1223 and 1273 K. The diffusion ability of Nd is weaker than that of As. Nd mainly diffuses through the Fe atomic vacancy mechanism. As mainly binds to Fe to form Fe and As compounds.

The influence of different heat preservation temperatures on the interaction in the Pr–Fe–As ternary system and the principle for generating the interaction products of the Pr–Fe–As ternary system were studied by metallographic microscopy, scanning electron microscopy, and x-ray diffraction. Results showed that the α-Fe with As (i.e., the compound formed when the solubility of As in Fe exceeds the maximum solubility), Fe2As, PrAs, and a small amount of Fe17Pr2 were the main products when the atomic ratio of Pr: As is 1:3 and heat preservation for 20 h at 1173 K, 1223 K and 1273 K. PrAs decreased as the temperature increased, while the α-Fe with As decreased as the temperature decreased, and Fe2As increased gradually as α-Fe with As decreased. In the Pr–Fe–As ternary system, the diffusion of Pr is mainly short-range diffusion and double vacancies, and the PrAs develops in the margin of the penetration region, preventing the diffusion of As in Fe.