Abstract In this paper, high purity cobalt (Co) powder and fine Y2O3 powder were used to fabricate Y2O3 doped Co bulks through ball milling and spark plasma sintering (SPS). The transformation from face-centered cubic (FCC) structure to hexagonal close-packed (HCP) structure during the cooling process after SPS was investigated. It has been shown that the addition of Y2O3 decreases significantly the grain size from 682 nm to 374 nm, since Y2O3 particles can effectively inhibit the grain growth by pinning the boundary migration. After doping the Y2O3, the FCC structured Co with a large volume fraction of over 70% can stably coexist with the HCP structured Co at room temperature, resulted from two possible reasons. First, Y2O3 particles hinder the dislocation movements. Second, Y2O3 particles occupy the deformation center of some defects in the FCC structure to reduce the number of potential nucleus of the HCP structure. In addition, due to the lower stacking fault energy of the FCC structured Co than that of the HCP structured Co, a lot of twins can be observed in the FCC grains in Y2O3 doped Co bulks after SPS.

中文翻译：

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Y 2 O 3 掺杂对球磨和放电等离子烧结钴中FCC到HCP相变的影响

摘要 本文采用高纯度钴（Co）粉和Y2O3细粉，通过球磨和放电等离子烧结（SPS）制备了掺杂Y2O3的Co块体。研究了 SPS 后冷却过程中面心立方 (FCC) 结构向六方密堆积 (HCP) 结构的转变。研究表明，Y2O3 的加入使晶粒尺寸从 682 nm 显着减小到 374 nm，因为 Y2O3 颗粒可以通过钉扎边界迁移有效地抑制晶粒生长。掺杂 Y2O3 后，体积分数超过 70% 的 FCC 结构的 Co 可以在室温下与 HCP 结构的 Co 稳定共存，这有两个可能的原因。首先，Y2O3 粒子阻碍了位错运动。第二，Y2O3 粒子占据了 FCC 结构中某些缺陷的变形中心，从而减少了 HCP 结构的潜在核数。此外，由于 FCC 结构的 Co 的堆垛层错能低于 HCP 结构的 Co，在 SPS 后，在 Y2O3 掺杂的 Co 块体中的 FCC 晶粒中可以观察到大量孪晶。