Microstructures and recrystallization behavior of severely hot-deformed tungsten
Microstructures and recrystallization behavior of severely hot-deformed tungsten
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DOI：
10.1016/j.msea.2008.03.051
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发表时间：
2009-03
期刊：
影响因子：
6.4
通讯作者：
S. Mathaudhu;A. Derosset;K. Hartwig;L. Kecskes
中科院分区：
文献类型：
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作者：
S. Mathaudhu;A. Derosset;K. Hartwig;L. Kecskes
粗晶钨（CG）经等径角挤压（ECAE）大量加工后，晶粒尺寸降至超细晶/纳米晶状态（UFG/NC），强度和延展性得到提高。由于cgw的脆性，材料必须进行热挤压，如果温度接近再结晶温度（Trc），则性能增益可能无法最大化。在这项研究中，ecae加工的CG W的再结晶行为作为传递应变（即挤压次数）和热加工挤压温度的函数进行了研究。在温度为1000°C或1200°C的条件下，在90°通道交叉处的模具中进行了多达4次ECAE通道。随后将加工材料退火60分钟至1600℃，以测定Trc。采用维氏显微硬度测量和扫描电镜对加工态和再结晶态的组织进行了表征。在完全工作状态下，随着应变的增加和热加工温度的降低，ecae处理的W的显微组织破裂和细化程度增加。trc被确定为~ 1400°C，这几乎与挤压次数和工作温度无关。这些结果表明，如果ECAE在1400°C以下完成（即在1000°C或更低），则UFG/ nc加工W的吸引特性可能会保留。具体来说，在1000°C以下，随着赋予材料的应变的增加，可以期望具有高硬度值并伴随晶粒尺寸细化（~ 350nm）。
When coarse-grained (CG) tungsten (W) is heavily worked by equal-channel angular extrusion (ECAE), the grain size is reduced to the ultrafine-grained/nanocrystalline regimes (UFG/NC) and the strength and ductility increase. Because of the brittle nature of CG W, the material must be hot-extruded, and, if the temperatures are near the recrystallization temperature (Trc), gains in properties may not be maximized. In this study, the recrystallization behavior of ECAE-processed CG W is examined as a function of the imparted strain (i.e., number of extrusions) and the hot-working extrusion temperature. Up to four ECAE passes were performed in tooling with a 90° channel intersection, and at temperatures of 1000°C or 1200°C. Subsequent 60min annealing of the worked material to 1600°C allowed for the determination of Trc. Vickers microhardness measurements and scanning electron microscopy, were used to characterize the microstructures in the as-worked and recrystallized states. The ECAE-processed W shows increased microstructural break-up and refinement with increasing strain and decreasing hot-working temperature in the fully worked state. Trcwas determined to be ∼1400°C, which is nearly independent of the number of extrusions and the working temperature. These results show that if ECAE is accomplished below 1400°C (i.e., at 1000°C or lower) the attractive properties of the UFG/NC-worked W may be retained. Specifically, below 1000°C, with increasing strain imparted to the material, high hardness values with a concomitant grain size refinement (∼350nm) could be expected.