Thermal Stability of Nonequilibrium Alloys Produced by Vapor quenching

在电子束沉积工艺中，高能蒸汽溶液被冷凝到冷基体上，获得了范围广泛的各种非平衡合金。虽然这些非平衡合金显示出优异的磁性和催化性能，但它们是热不稳定的。为了提高其热稳定性，我们研究了热处理对非平衡合金的结构和物理性能的影响：差示扫描量热法和测量的X射线衍射图，磁化强度和穆斯堡尔谱退火前后的红外图像炉。我们得到了以下结果。(1)非平衡二元晶态Fe-Cu和Fe-Ag合金以及三元非晶态Fe-Cu-Ag合金显示出软磁特性，即，矫顽力小于1 Oe和高磁通密度。而非平衡态Fe-Cu和Fe-Ag合金在300 ℃以上发生相分离，而非晶态Fe-Cu-Ag合金在130 ℃以上转变为bcc和fcc相。(2)非晶态Fe-Ti合金是一种良好的储氢和氢过滤材料。由于它们在高达约700 ℃的温度下是热稳定的，因此它们将被用作工业材料。(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，在制备状态下矫顽力小于10 Oe，通过在300 ℃以下退火，矫顽力变为约5 Oe。这些合金在300 ℃以上经历相分离，然而，它们在500 ℃退火后显示出非常有趣的磁特性，即，矫顽力约为500 Oe，磁通密度约为18 kOe，与Co-Ni磁记录介质相当或更高，目前我们正在研究非平衡合金的EXAFS谱和XPS谱及其退火后的变化。

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.