Taneike Masaki, Abe Fujio, Sawada Kota
Steel Research Center, and Materials Information Technology Station, National Institute for Materials Science,1-2-1 Sengen, Tsukuba 305-0047, Japan.
Nature. 2003 Jul 17;424(6946):294-6. doi: 10.1038/nature01740.
Creep is a time-dependent mechanism of plastic deformation, which takes place in a range of materials under low stress-that is, under stresses lower than the yield stress. Metals and alloys can be designed to withstand creep at high temperatures, usually by a process called dispersion strengthening, in which fine particles are evenly distributed throughout the matrix. For example, high-temperature creep-resistant ferritic steels achieve optimal creep strength (at 923 K) through the dispersion of yttrium oxide nanoparticles. However, the oxide particles are introduced by complicated mechanical alloying techniques and, as a result, the production of large-scale industrial components is economically unfeasible. Here we report the production of a 9 per cent Cr martensitic steel dispersed with nanometre-scale carbonitride particles using conventional processing techniques. At 923 K, our dispersion-strengthened material exhibits a time-to-rupture that is increased by two orders of magnitude relative to the current strongest creep-resistant steels. This improvement in creep resistance is attributed to a mechanism of boundary pinning by the thermally stable carbonitride precipitates. The material also demonstrates enough fracture toughness. Our results should lead to improved grades of creep-resistant steels and to the economical manufacture of large-scale steel components for high-temperature applications.
蠕变是一种随时间变化的塑性变形机制，它发生在多种材料中，且应力较低——即低于屈服应力的情况下。金属和合金通常可以通过一种称为弥散强化的工艺来设计，使其能够在高温下承受蠕变，在这种工艺中，细小颗粒均匀分布在整个基体中。例如，高温抗蠕变铁素体钢通过氧化钇纳米颗粒的弥散作用，在923K时达到最佳蠕变强度。然而，这些氧化物颗粒是通过复杂的机械合金化技术引入的，因此，大规模工业部件的生产在经济上是不可行的。在此，我们报告了使用传统加工技术生产的一种含有纳米级碳氮化物颗粒的9%Cr马氏体钢。在923K时，我们的弥散强化材料的断裂时间相对于目前最强的抗蠕变钢增加了两个数量级。这种抗蠕变性能的提高归因于热稳定碳氮化物析出物的边界钉扎机制。该材料还具有足够的断裂韧性。我们的研究结果应能带来更高等级的抗蠕变钢，并实现高温应用大型钢部件的经济制造。
