Universidad de Concepción, Departamento de Ingeniería de Materiales, Edmundo Larenas 270, Concepción, Chile.
AB SandvikCoromant R&D, Lerkrogsvägen 19, Stockholm, SE 126 80, Sweden.
J Nanosci Nanotechnol. 2019 May 1;19(5):2971-2976. doi: 10.1166/jnn.2019.15836.
A 12% Cr martensitic/ferritic with tailor-made microstructure was characterized by HRTEM after tempering (780 °C/2 h) and isothermal aging at 650 °C during 2 months and 1 year. The investigation was focused on the precipitation behavior of Laves phase nanoparticles and its contribution to creep response at 650 °C. Although, dense precipitation of Laves phase occurs during the heat treatment (196 nm), addition of 3.8% tungsten (W) promotes a high growth rate of this particle at 650 °C. The excessive addition of W induces a high driving force for the growth of this particle reaching a mean size of 300 nm at 2 months and 400 nm at 1 year. However, some small Laves phase nanoparticles inside the grain were detected at 1 year of isothermal aging, suggesting a low coarsening rate maybe due to low diffusion of W in the matrix. Results of creep test at 650 °C suggest most of the precipitation hardening is granted by fine dispersion of Ta-rich carbonitrides (Ta-MX), i.e., Laves phase is too coarse to contribute to the pinning force of the subgrain structure in the designed alloy.
经过回火（780°C/2 小时）和在 650°C 下进行 2 个月和 1 年的等温时效处理后，用高分辨透射电子显微镜（HRTEM）对具有定制微观结构的 12%Cr 马氏体-铁素体进行了表征。研究的重点是 Laves 相纳米颗粒的析出行为及其对 650°C 下蠕变响应的贡献。尽管在热处理过程中（196nm）发生了 Laves 相的密集析出，但添加 3.8%的钨（W）会促进该颗粒在 650°C 下的高生长速率。W 的过量添加会导致该颗粒的生长驱动力过高，在 2 个月时达到平均尺寸为 300nm，在 1 年时达到 400nm。然而，在 1 年的等温时效过程中，在晶粒内检测到一些较小的 Laves 相纳米颗粒，这表明由于 W 在基体中的扩散较低，可能导致其粗化速率较低。在 650°C 下的蠕变试验结果表明，大部分沉淀硬化是由富 Ta 的碳氮化物（Ta-MX）的细分散提供的，即 Laves 相太粗，无法对设计合金的亚晶粒结构的钉扎力做出贡献。
