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首页> 外文期刊>Physica, B. Condensed Matter >Study of ageing in Al-Mg-Si alloys by positron annihilation spectroscopy
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Study of ageing in Al-Mg-Si alloys by positron annihilation spectroscopy

机译：用正电子an没光谱研究Al-Mg-Si合金的时效

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In many common Al-Mg-Si alloys (6000 series) intermediate storage at or near 'room temperature' after solutionising leads to pronounced changes of the precipitation kinetics during the ensuing artificial ageing step at ≈180°C. This is not only an annoyance in production, but also a challenge for researchers. We studied the kinetics of natural 'room temperature' ageing (NA) in Al-Mg-Si alloys by means of various different techniques, namely electrical resistivity and hardness measurement, thermoanalysis and positron lifetime and Doppler broadening (DB) spectroscopy to identify the stages in which the negative effect of NA on artificial ageing might appear. Positron lifetime measurements were carried out in a fast mode, allowing us to measure average lifetimes in below 1 min. DB measurements were carried out with a single detector and a ~(68)Ge positron source by employing high momentum analysis. The various measurements show that NA is much more complex than anticipated and at least four different stages can be distinguished. The nature of these stages cannot be given with certainty, but a possible sequence includes vacancy diffusion to individual solute atoms, nucleation of solute clusters, Mg agglomeration to clusters and coarsening or ordering of such clusters. Positron lifetime measurements after more complex ageing treatments involving storage at 0°C, 20°C and 180°C have also been carried out and help to understand the mechanisms involved.
机译：在许多常见的Al-Mg-Si合金（6000系列）中，固溶后在“室温”或接近“室温”的中间存储会导致随后的≈180°C的人工时效步骤中析出动力学的明显变化。这不仅是生产中的烦恼，也是研究人员的挑战。我们通过各种不同的技术研究了Al-Mg-Si合金中自然“室温”时效（NA）的动力学，即电阻率和硬度测量，热分析和正电子寿命以及多普勒展宽（DB）光谱法，以识别各阶段。其中NA对人工老化的负面影响可能会出现。正电子寿命测量是在快速模式下进行的，这使我们能够在1分钟以内测量平均寿命。通过采用高动量分析，使用单个检测器和〜（68）Ge正电子源进行DB测量。各种测量结果表明，NA比预期的要复杂得多，并且至少可以区分四个不同的阶段。这些阶段的性质无法确定，但是可能的顺序包括空位扩散到各个溶质原子，溶质团簇成核，Mg团聚成团簇以及这些团簇的粗化或有序化。在进行了更复杂的老化处理（包括在0°C，20°C和180°C下存储）后，正电子寿命的测量也已进行，这有助于了解其中的机理。

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