The plastic deformation behavior of single crystals of Mo₅Si₃ with the tetragonal D8_m structure has been investigated in compression as a function of crystal orientation and temperature (1200–1500°C) in the bulk form and as a function of crystal orientation and specimen size at room temperature in the micropillar form. The slip system of {11$\overline{2}$}<111> is identified to be the only one that operates at high temperatures above 1200°C in bulk crystals, while any plastic flow is not detected at room temperature in micropillar crystals. The critical resolved shear stress (CRSS) for {11$\overline{2}$}<111> slip at room temperature estimated from the extrapolation of the temperature dependence of CRSS obtained for bulk crystals is considerably higher than fracture stresses obtained for micropillar crystals, indicating that the room-temperature brittleness is due in principle to the difficulty in dislocation motion arising from the very high CRSS value. The value of fracture toughness evaluated with a chevron-notched micro-beam specimen with a notch plane parallel to (001) is 1.54 MPa•m^1/2, which is comparable to those reported for other transition-metal (TM) silicides of the TM₅Si₃-type. The selection of {11$\overline{2}$} slip plane and the dissociation of the 1/2<111> dislocation on the slip plane are discussed based on generalized stacking fault energy (GSFE) curves theoretically calculated by first-principles calculations.

已经研究了具有四方 D8 _{m结构的 Mo 5} Si ₃单晶的塑性变形行为在压缩中作为晶体取向和温度（1200-1500°C）的函数的块状形式以及晶体取向和室温下微柱形式的试样尺寸。{11的滑移系统$\overline{2}$}<111> 被认为是唯一一种在 1200°C 以上的高温下在块状晶体中工作的晶体，而在室温下微柱晶体中未检测到任何塑性流动。{11 的临界分辨剪应力 (CRSS)$\overline{2}$}<111>室温滑移从块状晶体获得的 CRSS 的温度依赖性外推估计远高于微柱晶体获得的断裂应力，这表明室温脆性原则上是由于位错运动的困难由非常高的 CRSS 值引起。用缺口平面平行于 (001) 的 V 形缺口微梁试样评估的断裂韧性值为 1.54 MPa•m ^1/2，这与报道的其他过渡金属 (TM) 硅化物的值相当TM ₅ Si ₃型。{11的选择$\overline{2}$} 滑移面和1/2 111 位错在滑移面上的解离是基于广义层错能(GSFE)曲线，通过第一性原理计算得到的。