Creep Study of Aluminum and Magnesium Strengthened with High Volume Fractions of Oxide Dispersoids

9417636 Dunand该资助研究氧化物弥散强化（ODS）铝和镁合金的高温力学性能和微观结构。 颗粒尺寸、体积分数和晶粒尺寸的独特组合允许探测弥散强化的基本机制。 合金的特征在于氧化物具有：（1）体积分数为20 - 30体积%（高于机械合金化或沉淀强化合金的典型值）;（2）颗粒尺寸在0.2和0.8微米之间（小于金属基质复合材料，但大于机械合金化或快速凝固合金）;（3）晶粒尺寸非常细，0.5微米，或非常粗，1厘米，比大多数弥散强化合金跨越更大的尺寸范围。 样品在高温下以一定范围的应变率进行单轴拉伸试验。 透射电子显微镜用于研究位错与氧化物颗粒的相互作用。 这项研究允许检查的问题，如阈值应力的性质，在颗粒-基体界面的位错攀移现象，以及在弥散强化合金的变形晶粒和亚晶界的作用。%科学的目标是通过在不可剪切颗粒的体积分数非常高的新情况下的位错-颗粒相互作用的微观力学建模，将微观结构与机械性能相关联。 这项研究可能会导致改进的高温，轻质金属合金的结构应用。***

9417636 Dunand This grant examines the high temperature mechanical properties and microstructure of oxide dispersion strengthened (ODS) aluminum and magnesium alloys. A unique combination of particle size, volume fraction, and grain size allows the probing of the fundamental mechanisms of dispersion strengthening. The alloys feature oxides with: (1) volume fraction from 20 to 30 vol.% (above typical values for mechanically-alloyed or precipitation-strengthened alloys); (2) particle sizes between 0.2 and 0.8 microns (smaller than metal matrix composites, but larger than mechanically-alloyed or rapidly-solidified alloys); (3) grain sizes that are either very fine, 0.5 microns, or very coarse, 1 centimeter, spanning a larger range of sizes than most dispersion strengthened alloys. Samples are tested in uniaxial tension at elevated temperatures in a range of strain rates. Transmission electron microscopy is used to study dislocation interaction with oxide particles. This research allows examination of issues such as the nature of the threshold stress, dislocation climb phenomena at particle-matrix interfaces, and the role of grain and subgrain boundaries in the deformation of dispersion-strengthened alloys. %%% The scientific goal is to correlate the microstructure with the mechanical properties through micromechanical modeling of the dislocation-particle interactions in the novel situation of very high volume fractions of unshearable particles. This research could lead to improved high temperature, lightweight metal alloys for structural applications. ***