Kinetics of precipitation in 17–4 PH stainless steel
Kinetics of precipitation in 17–4 PH stainless steel
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DOI：
10.1179/mst.1989.5.4.346
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发表时间：
1989-04
影响因子：
1.8
通讯作者：
U. Viswanathan;P. Nayar;R. Krishnan
中科院分区：
文献类型：
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作者：
U. Viswanathan;P. Nayar;R. Krishnan
通过观察17- 4PH（沉淀硬化）不锈钢在320-600°C范围内不同温度等温时效时的电阻率和显微组织，研究了该合金的沉淀顺序及其动力学。由孵化期的情况下，沉淀的开始，它表明，没有自由能垒成核。随着老化时间的延长，样品的电阻率逐渐下降，并随着时间的推移逐渐接近稳定值。发现在高于550°C下老化的合金具有比在较低温度下老化的合金更高的最终电阻率值。通过透射电子显微镜观察，在高于550°C的温度下时效的试样中，由于板条边界处铜原子的增强扩散和集中，马氏体向奥氏体的局部逆转被揭示。沉淀动力学符合Johnson-Mehl方程。根据电阻率测量，沉淀过程的活化能Q估计为112·2 ± 3·6 kJ mol-1。这可以理解为铜原子在过饱和基体中的增强扩散，这是由较高的位错密度和较高浓度的淬入空位引起的。MST/826
The sequence of precipitation and its kinetics in 17–4 PH (precipitation hardening) stainless steel were studied by observing the electrical resistivity and microstructure of the alloy during isothermal aging at various temperatures in the range 320–600°C. By the absence of an incubation period for the onset of precipitation it is shown that there is no free energy barrier to nucleation. The electrical resistivity of the specimen decreased on prolonged aging approaching a steady value asymptotically with time. The alloys aged above 550°C were found to have higher final resistivity values than those aged at lower temperatures. By transmission electron microscopy, local reversion of the martensite to austenite, attributed to enhanced diffusion and concentration of copper atoms at the lath boundaries, was revealed in the specimens aged at temperatures above 550°C. The kinetics of precipitation in the system obeyed the Johnson–Mehl equation. The activation energy Q of the precipitation process was estimated to be 112·2 ± 3·6 kJ mol−l from the resistivity measurements. This may be understood in terms of an enhanced diffusion of copper atoms in the supersaturated matrix caused by a higher dislocation density and a higher concentration of quenched-in vacancies. MST/826