Thermal Stability of Nonequilibrium Alloys Produced by Vapor quenching

在溅射沉积过程中，高能蒸气溶液被冷凝成亚态，得到了范围广泛、种类繁多的非平衡合金。尽管这些非平衡合金表现出优异的磁性和催化性能，但它们在热稳定性方面是不稳定的。为了提高非平衡合金的热稳定性，我们研究了热处理对非平衡合金结构和物理性能的影响：用差示扫描量热法测定了非平衡合金在红外成像炉中退火前后的X射线衍射谱、磁化强度和穆斯堡尔谱。结果表明：(1)非平衡二元晶态Fe-Cu和Fe-Ag合金和三元非晶态Fe-Cu-Ag合金表现出软磁特性，即矫顽力小于10E，磁感应强度高。然而，非平衡的bcc和fcc的Fe-Cu和Fe-Ag合金在300℃以上发生相分离，而非晶态的Fe-Cu-Ag合金在130℃以上转变为bcc和fcc相。(2)非晶态Fe-Ti合金具有良好的储氢和氢过滤性能。(3)在非平衡Fe-Pd合金中，Fe原子的磁矩增大，表现出软磁特性，即在制备时的矫顽力小于10Oe，在300℃以下退火后约为5Oe。这些合金在300℃以上经历了相分离，但在500℃热处理后，它们表现出非常有趣的磁性特征，即矫顽力约为500Oe，磁通密度约为18Koe，与Co-Ni磁记录介质相当或更好的。现在，我们正在研究非平衡合金的EXAFS谱和XPS谱以及它们在退火热处理中的变化。

In sputter-deposition process a high energy vapor solution is condenced onto a cold substate and a wide range and a wide variety of nonequilibrium alloys have been obtained. Although these nonequilibrium alloys reveal excellent magnetic and catalytic properties, they are thermally unstable. In order to improve their thermal stability we have studied effects of heat treatments on the structure and physical properties of nonequilibrium alloys: differential scanning calorimetry and measurements of X-ray diffraction patterns, magnetization and Mossbauer spectra before and after annealing in an infra-red image furnace. We have obtained the following results.(1) Nonequilibrium binary crystalline Fe-Cu and Fe-Ag alloys and ternary amorphous Fe-Cu-Ag alloys show a soft magnetic characteristic, i.e., the coercive force less than 1 oe and high magnetic flux density. However, the nonequilibrium bcc and fcc Fe-Cu and Fe-Ag alloys undergo a phase separation above 300 C, while the amorphous Fe-Cu-Ag alloys transform to bcc and fcc phases above 130 C.(2) Amorphous Fe-Ti alloys are good hydrogen storage and good hidrogen filters. Since they are thermally stable up to about 700 C, they will be used as industrial materials.(3) In nonequilibrium Fe-Pd alloys, the magnetic moment of Fe atoms are enlarged and a soft magnetic characteristic is observed, i.e., the coercive force is less than 10 Oe in the as-prepared state and it becomes about 5 Oe by annealing below 300 C. These alloys undergo a phase separation above 300 C, however, they show very interesting magnetic characteristics aFter annealing at 500 C, i.e., the coercive force is about 500 Oe and the magnetic flux density is about 18 kOe, being comparable to or getter than those of Co-Ni magnetic recording media.Now, we are studying EXAFS spectra and XPS spectra of the nonequilibrium alloys and their variation by annealing.