Metastable phases produced by laser melt quenching

A Nd: glass laser has been used to produce and retain metastable phases which are similar to phases obtained by rapid quenching (“splat cooling”) techniques. A single laser pulse of 10 msec duration was focused onto the surface of an alloy specimen to provide a beam intensity of approximately 3.7 × 10⁵ watts per sq cm. A small volume of metal in the relatively large specimen immediately underwent melting. Upon cessation of the laser pulse, the molten metal solidified very quickly. Extremely rapid cooling was achieved due to the presence of nearly ideal conditions for conduction cooling. Laser melting of various alloys of the eutectic Ag-Cu system resulted in a complete series of solid solutions, as verified by X-ray analysis. In addition, the laser melt quenching technique provided a threefold increase in microhardness of the resolidified metal. Formerly Western Electric Engineering Research Center, Princeton, N. J. 08540     

固态和液态钢的激光诱导等离子体比较

比较了产生于室温固态钢以及高温液态钢上激光诱导等离子体的特征、原子铁的激发温度以及电子密度。通过在386～400nm波长范围的中性铁原子发射谱线, 由波尔兹曼作图法确定了铁原子的激发温度。通过测量AlI394.4nm的谱线宽度, 估算了电子密度。对固体钢来说, 铁元素的激发温度从延迟时间为10μs时的10800K下降到延迟时间为80μs时的7300K。当延迟时间分别为10μs和70μs时, 产生于固态钢和液态钢上等离子体间的激发温度并没有显著差别。在铁元素和铝元素大部分的中性原子线中, 可以观察到液态钢的谱线宽度比固态钢的谱线宽度更窄。当激光脉冲的观察延迟时间均为10μs时, 产生于液态钢上等离子体的电子密度大约为(0.99±0.15)×10¹⁷/cm³, 这相当于产生在固态钢上等离子体电子密度的46%。