Benjamin Milkereit , Christian Rowolt , Dipanwita Chatterjee , Randi Holmestad , Ruben Bjørge , Matteo Villa , Frank Niessen , Andreas Stark , Frédéric De Geuser , Olaf Kessler
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引用次数: 0
Abstract
In this work, the transformation and dissolution/precipitation behaviour of the soft martensitic, precipitation-hardening steel X5CrNiCuNb16-4 (often referred to as 17–4 PH or AISI 630) has been investigated by various analytical in situ techniques. First, austenite formation during the heating stage of a solution treatment (or austenitization) is examined. Subsequently, a major part of this work evaluates precipitation during cooling from the solution treatment (i.e., the quench-induced precipitation of Cu-rich particles). The following analytical in situ techniques were utilised: synchrotron high-energy X-ray diffraction, synchrotron small-angle X-ray scattering, differential scanning calorimetry, and dilatometry. These were complemented by ex situ high-angle annular dark-field scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy on as-quenched samples after various cooling rates. The continuous heating transformation and continuous cooling transformation diagrams have been updated. Contrary to previous reports, X5CrNiCuNb16-4 is rather quench sensitive and the final properties after ageing degrade if cooling is done slower than a certain critical cooling rate. Quench-induced Cu-rich precipitation happens in two reactions: a larger, nearly pure Cu face-centred cubic phase forms at higher temperatures, while at medium temperatures, spherical Cu-rich nanoparticles form, which are found to be body-centred cubic at room temperature. The dimensions of the quench-induced particles range from several µm after cooling at 0.0001 K s-1 down to just a few nm after cooling at 1 K s-1. The maximum age hardening potential of X5CrNiCuNb16-4 can be exploited if a fully supersaturated solid solution is reached at cooling rates above the critical cooling rate of about 10 K s-1.
在这项工作中,采用各种原位分析技术研究了软马氏体沉淀硬化钢 X5CrNiCuNb16-4(通常称为 17-4 PH 或 AISI 630)的转变和溶解/沉淀行为。首先,研究了固溶处理(或奥氏体化)加热阶段奥氏体的形成。随后,这项工作的主要部分是评估固溶处理冷却过程中的沉淀(即淬火诱发的富铜颗粒沉淀)。采用了以下原位分析技术:同步辐射高能 X 射线衍射、同步辐射小角 X 射线散射、差示扫描量热和膨胀测量。此外,还采用了高角度环形暗场扫描透射电子显微镜和能量色散 X 射线光谱法,对不同冷却速率后的淬火样品进行了分析。连续加热转化图和连续冷却转化图已经更新。与之前的报告相反,X5CrNiCuNb16-4 对淬火相当敏感,如果冷却速度慢于某个临界冷却速度,则老化后的最终性能会下降。淬火诱导的富铜析出分为两种反应:在较高温度下形成较大的、近乎纯铜的面心立方相,而在中等温度下则形成球形富铜纳米颗粒,在室温下为体心立方相。淬火诱导颗粒的尺寸范围从以 0.0001 K s-1 冷却后的几微米到以 1 K s-1 冷却后的几纳米不等。如果在冷却速率高于临界冷却速率(约 10 K s-1)时达到完全过饱和固溶体,则可利用 X5CrNiCuNb16-4 的最大时效硬化潜力。
期刊介绍:
Materialia is a multidisciplinary journal of materials science and engineering that publishes original peer-reviewed research articles. Articles in Materialia advance the understanding of the relationship between processing, structure, property, and function of materials.
Materialia publishes full-length research articles, review articles, and letters (short communications). In addition to receiving direct submissions, Materialia also accepts transfers from Acta Materialia, Inc. partner journals. Materialia offers authors the choice to publish on an open access model (with author fee), or on a subscription model (with no author fee).