Accelerated Coarsening of MX Carbonitrides in 12%Cr Steels during Creep Deformation
Accelerated Coarsening of MX Carbonitrides in 12%Cr Steels during Creep Deformation
复制标题
加速%20粗化%20of%20MX%20碳氮化物%20in%2012%Cr%20钢%20期间%20蠕变%20变形
DOI：
10.2355/isijinternational.41.suppl_s111
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发表时间：
2001
影响因子：
1.8
通讯作者：
T. Morimoto
中科院分区：
文献类型：
--
作者：
Taneike Masaki;M. Kondo;T. Morimoto
MX碳氮化物（M=Nb，V，Ta/X=C，N）弥散分布在12%Cr铁素体耐热钢基体中，通过沉淀强化机制提高钢的蠕变强度。然而，MX颗粒在高温蠕变变形过程中通常会粗化，这导致蠕变强度下降。为了研究12%Cr钢（10.5Cr-0.1C-（Nb，V，Ta））中MX颗粒的粗化过程，从蠕变试样断裂后的夹持部分（无蠕变应力区）和计量部分（应力区）制备了TEM试样。测量部分中MX颗粒半径的变化显著大于握杆部分中的MX颗粒半径的变化，表明蠕变应力加速了测量部分中MX颗粒的奥斯特瓦尔德熟化。基于Nb和V不仅可以通过晶格扩散机制扩散而且可以通过位错扩散机制扩散的假设，通过引入有效扩散系数作为晶格扩散系数和位错扩散系数的总和来修改Ostwald熟化方程。应变片部分中的位错扩散的影响大于夹持部分中的位错扩散的影响，因为应变片部分中的位错通过蠕变应力移动，并且溶质原子沿着位错扩散的速率可能增加。用改进的成熟方程可以较好地模拟MX颗粒在规范区的粗化过程。
MX carbonitrides (M=Nb, V, Ta/X=C, N), which are finely dispersed in the matrix of 12%Cr ferritic heat resistance steels, increase the creep strength of the steels by the precipitation strengthening mechanism. However, MX particles usually coarsen during high temperature creep deformation, and this results in a decrease of creep strength. In order to clarify the coarsening process of MX particles in 12%Cr steels (10.5Cr-0.1C-(Nb, V, Ta)), TEM samples were prepared from the grip portion (creep stress free zone) and the gauge portion (stress zone) of ruptured creep test pieces. The changes of MX particle radii in the gauge portion were considerably larger than that in the grip portion, indicating that creep stress accelerated Ostwald ripening of the particles in the gauge portion. The Ostwald ripening equation was modified by introducing the effective diffusion coefficient as a sum of the lattice diffusion coefficient and dislocation diffusion coefficient, based on an assumption that Nb and V might diffuse not only by the lattice diffusion mechanism but also by the dislocation diffusion mechanism. The effect of dislocation diffusion in the gauge portion was larger than that in the grip portion because dislocations in the gauge portion were moved by creep stress, and a rate of solute atoms diffusing along the dislocations might be increased. The coarsening process of MX particles in the gauge portion could be simulated successfully by means of a modified ripening equation.