Size-dependent fracture toughness of bulk-metallic glasses
Size-dependent fracture toughness of bulk-metallic glasses
复制标题
DOI：
10.1016/j.actamat.2014.01.062
复制
发表时间：
2014-05
期刊：
影响因子：
9.4
通讯作者：
B. Gludovatz;S. Naleway;R. Ritchie;J. Kruzic
中科院分区：
文献类型：
--
作者：
B. Gludovatz;S. Naleway;R. Ritchie;J. Kruzic
断裂韧性是决定材料工程性能的一项关键性能。然而，众所周知，对于晶体材料，如果不满足某些样品几何形状和尺寸要求，测试结果就会依赖于样品大小，难以在不同研究之间进行比较。本文采用不同尺寸的zr基块状金属玻璃（BMG） Zr52.5Cu17.9Ni14.6Al10Ti5（Vitreloy 105）试样，采用压紧拉伸法和单刃缺口弯曲法分别测量kic值和jic值，分别按ASTM E399标准和E1820标准测量。由此得出结论，应谨慎接受ASTM标准E399样品大小要求，以提供与尺寸无关的（有效的）kic结果；然而，也得出结论，小尺寸的样品可能会导致条件韧性kq值的更大分散，有效测试的产量更小，可能在某种程度上提高韧性值。这种行为不同于结晶金属，其中ASTM标准E399的尺寸要求相当保守。对于bmg来说，kq值随着未开裂韧带宽度的减小而增加，并表现出较大的散点，这也与结晶金属不同。小于ASTM标准要求的样品，可根据j -积分标准E1820进行测试；然而，在这项关于bmg的研究中，与有效测试结果相比，发现这样的测试给出了显着更高的韧性值。总的来说，bmg的韧性行为比结晶金属对尺寸要求更敏感，这可能与金属玻璃的弯曲延展性和应变软化行为的不同尺寸相关。结论是，在BMG样品上测量的韧性值小于kic标准的要求，这在文献中很常见，可能是样本量和几何相关的，即使它们满足较少限制的有效性要求。
The fracture toughness is a critical material property that determines engineering performance. However, as is well known for crystalline materials, if certain sample geometry and size requirements are not met, test results become sample-size dependent and difficult to compare between different studies. Here, the room-temperature fracture toughness of the Zr-based bulk metallic glass (BMG) Zr52.5Cu17.9Ni14.6Al10Ti5(Vitreloy 105) was evaluated using compact-tension, as well as single-edge notched-bend, specimens of different sizes to measureKIcvalues according to ASTM standard E399 andJIcvalues according to ASTM standard E1820. It is concluded that the ASTM standard E399 sample-size requirements should be cautiously accepted as providing size-independent (valid)KIcresults for BMGs; however, it is also concluded that small-sized samples may result in a wider scatter in conditional toughnessKQvalues, a smaller yield of valid tests and possibly somewhat elevated toughness values. Such behavior is distinct from crystalline metals where the size requirements of ASTM standard E399 are quite conservative. For BMGs,KQvalues increase and show a larger scatter with decreasing uncracked ligament widthb, which is also distinct from crystalline metals. Samples smaller than required by ASTM standards forKIctesting are allowed by theJ-integral-based standard E1820; however, in this study on BMGs, such tests were found to give significantly higher toughness values as compared to validKIcresults. Overall, the toughness behavior of BMGs is more sensitive to size requirements than for crystalline metals, an observation that is likely related to the distinct size-dependent bending ductility and strain softening behavior found for metallic glasses. It is concluded that toughness values measured on BMG samples smaller than that required by theKIcstandard, which are common in the literature, are likely sample size- and geometry-dependent, even when they meet the less restrictive validJIcrequirements.