Production of Nonequilibrium Alloy Powders by Ultrasonic and High-Pressure Gas Atomization Method and their Properties

设计并构建了一种新型的超声高压气体雾化液体淬火设备，旨在开发一种有效制备非晶球形粉末的方法。研究了在铁基和钴基合金体系中制备非晶粉末的诸多因素，确定了制备非晶粉末的雾化条件。随后，采用高温压烧结的方法对非晶粉末进行固结试验。结果表明，球形粉末固结困难，片状粉末与球形粉末混合对非晶块体的形成非常有效。根据这些信息，对雾化设备进行了改进，以生产片状粉末和球形粉末。在改造中，将旋转器设置在气体雾化喷嘴正下方的位置，通过旋转器将雾化后的小液滴压平，形成厚度为1 ~ 3 m的片状粉末。此外，弛豫热远大于熔体纺丝带的弛豫热，表明两段淬火方法获得了更高的冷却速度。冷却速度的增加可能是由于气体雾化产生的过冷液滴的后续冷却。此外，两段淬火技术还能在Fe-C二元合金等新型合金体系中形成玻璃，并显著扩大了玻璃形成合金体系的形成范围。超声和高压气体雾化后过冷液滴冲击压平的两段淬火技术的这些特点足以证明两段淬火技术及其非平衡合金粉末的进一步发展是有吸引力的。

A new liquid quenching equipment by utilizing an ultrasonic and high-pressure gas atomization method was designed and constructed with the aim of developing a method which can produce effectively amorphous spherical powders. Many factors of producing amorphous powders in Fe- and Co-based alloy systems were investigated and the atomization condition of producing the amorphous powders was established. Subsequently, the consolidation of the amorphous powders was tried by press-sintering at elevated temperatures. As a result, it was clarified that the consolidation is difficult for the spherical powders and the mixing of flaky powders to the spherical powders is very effective for the formation of amorphous bulks. From this information, the atomization equipment was modified so as to produce flaky powders as well as spherical powders. In the modification, the rotator was set up at the position just below the gas atomization nozzle and small atomized liquid droplets were flattened by the rotator, resulting in the formation of flaky powders with a small thickness of 1 to 3 m. Furthermore, the heat of relaxation was much larger than that for the melt-spun ribbons, indicating the achievement of much higher cooling velocities by the two-stage quenching method. The increase of cooling velocity is probably due to the subsequent cooling of super-cooled liquid droplets produced by gas atomization. In addition, the two-stage quenching technique was found to bring about the glass formation in new alloy systems such as Fe-C binary alloys and a remarkable extension of glass formation range in glass-forming alloy systems. These features of the newly developed two-stage quenching technique consisting of ultrasonic and high-pressure gas atomization followed by impact flattening of the supercooled liquid droplets are concluded to be attractive enough to confirm further progress of the two-stage quenching technique and the resulting nonequilibrium alloy powders.