用磁分析法观察某些铁-镍-铝合金的脱溶过程

用热磁分析方法较仔细地观测了Fe-Ni-Al三元系合金沿β+β′两相区内某一结线上的几个不同成分的合金样品。淬火所得的成分接近Fe₂NiAl的过饱和固溶体在较高温度(～850℃)分解甚快,在一分钟内脱溶基本上完成。在850℃分出的β′相还含铁约35at.％,其居里点在400℃附近。在850℃经短时间回火继以水淬的合金,在600—700℃再经适当的回火,则首次回火所生成的β′相继续迅速分解,在不超过十分钟内损失大量的铁而变成非铁磁性的;其在室温的H_c可增到500奥斯特。这和Б.Г.Лившнц所提出的“继续脱溶”的假设相符。磁性观测的结果证明:β′相的继续脱溶是“可逆的”,就是说,把曾在600—700℃回火的合金重热至850℃时β′相能在几分钟内恢复850℃的平衡成分。Fe₂NiAl过饱和固溶体在较低温度(70O℃以下)分解极慢,并且其过程是明显地“不均匀”的。因此,这种合金不能通过高温淬火继以较低温度(600—700℃)回火的处理来获得高H_c的事实可以用单畴粒子的理论加以解释。

A MAGNETIC STUDY OF SOME IRON-NICKEL-ALUMINUM ALLOYS

A detailed thermomagnetic analysis was carried out on a number of alloys along a tie-line in the two-phase (β+β′) region of the Fe-Ni-Al ternary system. The supersaturated solid solution, obtained by quenching an alloy close to the composition Fe₂NiAl, broke up very fast at relatively high temperatures （～850℃), precipitation being completed in a little more than a minute. The β′ phase formed at 850℃ still contained about 35 at. % iron, with a Curie point near 400℃. When this alloy, after going through such a short tempering at 850℃ followed by quenching, was heated up to 600-700℃ again, the β′ phase formed during the first tempering continued to decompose rapidly, losing enough iron to become nonmagnetic in not much more than ten minutes. This caused the room-temperature coercive force of the alloy to rise to about 500 Oe. Such a phenomenon is in agreement with Б．Г．Лившнц's. suggestion of "post-precipitation". The magnetic measurements showed, moreover, that the post-precipitatioa of the β′ phase was "reversible", that is, when the alloy was brought up to 850℃ again after quenching from the second tempering at 600-700℃, the β′ phase could recover its equilibrium composition for 850℃ in a few minutes. Decomposition of the supersaturated solid solution Fe₂NiAl at relatively low temperatures (below 700℃) was quite slow, and, furthermore, there was considerable evidence that the process was "non-uniform". On the basis of the above findings, the fact that high coercive force in the alloy Fe₂NiAl cannot be obtained by quenching from above the solution temperature plus tempering at relatively low temperatures (600-700℃) is interpreted in the light of the single-domain particle theory.