Abstract Within the temperature range over which the shear band (SB)-mediated plastic deformation is dominant, metallic glasses exhibit an intermediate temperature ductility minimum (ITDM), which occurs at about 65% of the glass transition temperature, T g . This ITDM is associated with a small number of SBs, with each band carrying large amount of plastic strain, which in turn leads to their easy transition to shear cracks, eventually leading to fracture. Some MGs are known to exhibit high room temperature (RT) fracture toughness, which has been associated with SB-mediated crack-tip plasticity. Hence, it is expected that ITDM would also correspond to a minimum in toughness. In order to ascertain this, temperature-dependence of mode I fracture toughness, J c , of a bulk metallic glass (BMG), Vitreloy 105, was investigated by recourse to 4-point bend testing of single edge notched specimens within 298–475 K range, which corresponds to ∼0.44 and 0.7 T g of the tested BMG. Complementary finite element analyses were utilized to convert the critical load for fracture into J c . Results confirm a minimum in J c at ∼0.67 T g , which is in agreement with the results of unnotched 3-point bend experiments on unnotched bars that show ITDM at 0.65 T g . These observations are rationalized with the aid of notch plastic deformation and post mortem fractographic characterizations and in terms of the influence of temperature on factors such as the number of shear bands, the barrier for their conversion into shear cracks, and hydrostatic stress gradients ahead of the notch tip. This study highlights the sensitive nature of BMGs' fracture toughness, even when they are nominally ductile, to temperature.

中文翻译：

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块状金属玻璃的 I 型断裂韧性的温度依赖性

摘要 在剪切带 (SB) 介导的塑性变形占主导地位的温度范围内，金属玻璃表现出中间温度延展性最小值 (ITDM)，发生在玻璃化转变温度 T g 的 65% 左右。这种 ITDM 与少量 SB 相关，每个带都带有大量的塑性应变，这反过来又导致它们容易转变为剪切裂纹，最终导致断裂。已知一些 MG 表现出高室温 (RT) 断裂韧性，这与 SB 介导的裂纹尖端塑性有关。因此，预计 ITDM 也将对应于韧性的最小值。为了确定这一点，块状金属玻璃 (BMG) Vitreloy 105 的模式 I 断裂韧性 J c 的温度依赖性，通过在 298-475 K 范围内对单边缺口试样进行 4 点弯曲测试进行研究，这对应于测试 BMG 的~0.44 和 0.7 T g。利用互补有限元分析将断裂的临界载荷转换为J c 。结果证实了约 0.67 T g 处的 J c 最小值，这与显示 ITDM 为 0.65 T g 的无缺口杆上无缺口 3 点弯曲实验的结果一致。借助缺口塑性变形和验尸断口特征，以及温度对剪切带数量、剪切裂缝转化为剪切裂纹的障碍以及流体静力应力梯度等因素的影响，这些观察结果得以合理化。缺口提示。这项研究强调了 BMGs 断裂韧性的敏感性，