Department of Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany.
Department of Materials, Imperial College London, Royal School of Mine, London, United Kingdom.
PLoS One. 2020 Apr 2;15(4):e0231179. doi: 10.1371/journal.pone.0231179. eCollection 2020.
Site-specific atom probe tomography (APT) from aluminum alloys has been limited by sample preparation issues. Indeed, Ga, which is conventionally used in focused-ion beam (FIB) preparations, has a high affinity for Al grain boundaries and causes their embrittlement. This leads to high concentrations of Ga at grain boundaries after specimen preparation, unreliable compositional analyses and low specimen yield. Here, to tackle this problem, we propose to use cryo-FIB for APT specimen preparation specifically from grain boundaries in a commercial Al-alloy. We demonstrate how this setup, easily implementable on conventional Ga-FIB instruments, is efficient to prevent Ga diffusion to grain boundaries. Specimens were prepared at room temperature and at cryogenic temperature (below approx. 90K) are compared, and we confirm that at room temperature, a compositional enrichment above 15 at.% of Ga is found at the grain boundary, whereas no enrichment could be detected for the cryo-prepared sample. We propose that this is due to the decrease of the diffusion rate of Ga at low temperature. The present results could have a high impact on the understanding of aluminum and Al-alloys.
基于铝合金的特定位置原子探针层析技术（APT）受到样品制备问题的限制。实际上，传统上用于聚焦离子束（FIB）制备的镓（Ga）对铝晶界具有高亲和力，并使晶界脆化。这导致在样品制备后晶界处 Ga 的浓度很高，从而导致成分分析不可靠，样品产量低。在这里，为了解决这个问题，我们建议使用低温聚焦离子束（cryo-FIB）专门从商业铝合金中的晶界制备 APT 样品。我们展示了这种设置如何在传统的 Ga-FIB 仪器上很容易实现，从而有效地防止 Ga 扩散到晶界。对在室温下和低温（约 90K 以下）下制备的样品进行了比较，并证实了在室温下，晶界处 Ga 的浓度超过 15%，而对于低温制备的样品则未检测到富集。我们认为这是由于低温下 Ga 的扩散速率降低所致。本研究结果对理解铝和铝合金具有重要影响。
