This paper has investigated the deformation behaviours and the size effect on the yielding of Mg₂₄Y₅ using nanoindentation, micro-pillar compression and in-situ TEM compression. The elastic modulus and hardness are measured to be 54.2 GPa and 3.2 GPa, respectively. The displacement discontinuities (i.e. pop-in) on the load-displacement curves were observed both in nanoindentation and in-situ TEM compression. It has been found that the primary slip system activated in the tests was $\frac{1}{2}111\left\{011\right\}$ regardless of the sample size and sample surface acted as the initial dislocation source. Molecular dynamics simulation showed that shear band was found to act as dislocation source with a configuration similar to Frank-Reed source. The deformation microstructure was studied using transmission electron microscopy. The sample size effect on the critical resolved shear stress measured from Mg₂₄Y₅ follows a power-law relationship with the estimated critical resolved shear stress for bulk sample of 265 MPa. It is suggesting that the observed size effect is due to the different dislocation source lengths which led to different stresses required for nucleation dislocations.

本文利用纳米压痕、微柱压缩和原位 TEM 压缩研究了变形行为和尺寸对 Mg ₂₄ Y ₅屈服的影响。弹性模量和硬度测得分别为 54.2 GPa 和 3.2 GPa。在纳米压痕和原位 TEM 压缩中都观察到了载荷-位移曲线上的位移不连续性（即弹出）。已经发现，在测试中激活的主滑动系统是$\frac{1}{2}111\left\{011\right\}$无论样品大小和样品表面如何，都充当初始位错源。分子动力学模拟表明，剪切带被发现充当位错源，其配置类似于弗兰克-里德源。使用透射电子显微镜研究变形微观结构。样品尺寸对从 Mg ₂₄ Y ₅测量的临界分辨剪应力的影响与 265 MPa 大块样品的估计临界分辨剪应力呈幂律关系。这表明观察到的尺寸效应是由于不同的位错源长度导致成核位错所需的不同应力。