低碳Mn-Mo钢及铁镍合金晶界硼非平衡偏聚的发生与发展过程是一种动力学现象。首次观察到在等温过程中晶界会产生比平衡偏聚高很多倍的非平衡硼偏聚.但随等温时间延长,过量偏聚逐步消失.等温时偏聚量出现峰值型变化是这类偏聚非平衡特性的重要标志. 不同温度等温时,硼偏聚量随时间变化曲线呈三种类型,其特征是出现峰值后偏聚逐步消失、部分消失和不消失.
The behaviour of grain bondary segregation and precipitation of B in B-bearing low C Mn-Mo steels and Fe-30%Ni alloys during isothermal holding has been investigated with particle tracking autoradiography. Specimens were quenched from 1350 or 1200℃ then isothermally held at 550—1000℃ for different periods. It is shown that the nonequilibrium grain boundary segregation pf B occurs as a dynamic process and the magnitude of it could be many times as large as that of equilibrium segregation. After cooling from the higher temperature, the B segregation, which is probably brought there by the complex of B atoms with supersaturated vancancies, increases at first with time, then upon the annihilation of vacancies, it becomes supersaturated with respect to equilibrium segregation concentration and thus decreases by diffusing back into the grains, giving a peak on the degree of segregation-holding time curve. The height and position of the peak depends on the initial heating and subsequent holding temperature. On the otherhand, if the holding temperature is lower, the nonequilibriumly segregated B becomes supersaturating and will precipitate at the grain boundaries, giving a curve increasing at first stage and then reaching a steady segregation. Thus, three kinds of grain boundary segregation kinetic curves are obtained at different isothermal temperatures.
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| [1] | |
| [2] | |
| [3] | |
| [4] | |
| [5] | |
| [6] | |
| [7] | |
| [8] | |
| [9] | |
| [10] | |
| [11] | |
| [12] |
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