Energy dissipation in fracture of bulk metallic glasses via inherent competition between local softening and quasi-cleavage
Energy dissipation in fracture of bulk metallic glasses via inherent competition between local softening and quasi-cleavage
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DOI：
10.1080/14786430701864753
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发表时间：
2008-01-01
影响因子：
1.6
通讯作者：
Dai, L. H.
中科院分区：
文献类型：
--
作者：
Jiang, M. Q.;Ling, Z.;Dai, L. H.
对典型坚韧Zr 41.2Ti 13.8Cu 10 Ni 12.5Be 22.5（Vit 1）块体非晶合金（BMG）在10（-4）~ 10（6）s（-1）的应变速率范围内进行了压缩、拉伸和高速平板冲击实验。令人惊讶的是，在这种坚韧维生素1的动态模式I断裂表面上也观察到纳米级的细凹窝和周期性波纹。以广泛的概述试样的断裂模式，我们提出了一个标准，以评估是否BMG断裂本质上是脆性或塑性。如果裂纹尖端的曲率半径大于弯月面失稳的临界波长[F。Spaepen，Acta Metall. 23 615（1975）; A.S. Argon和M.你好脱线Sci. Eng.23219（1976）]，在裂纹表面上出现微尺度脉纹图案和纳米级凹坑。然而，在相反的情况下，局部准解理/分离通过局部原子团簇与局部软化的背景中领先的裂纹尖端占主导地位，产生纳米级的周期性波纹。因此，在原子团簇水平上，BMG断裂中的能量耗散由两个相互竞争的基本过程决定，即裂纹尖端前方的常规剪切转变区（STZ）和设想的拉伸转变区（TTZ）。最后，应用该能量耗散机制，定量地讨论了纳米周期性位错的形成机理。
Compression, tension and high-velocity plate impact experiments were performed on a typical tough Zr41.2Ti13.8Cu10Ni12.5Be22.5 (Vit 1) bulk metallic glass (BMG) over a wide range of strain rates from similar to 10(-4) to 10(6) s(-1). Surprisingly, fine dimples and periodic corrugations on a nanoscale were also observed on dynamic mode I fracture surfaces of this tough Vit 1. Taking a broad overview of the fracture patterning of specimens, we proposed a criterion to assess whether the fracture of BMGs is essentially brittle or plastic. If the curvature radius of the crack tip is greater than the critical wavelength of meniscus instability [F. Spaepen, Acta Metall. 23 615 (1975); A.S. Argon and M. Salama, Mater. Sci. Eng. 23 219 (1976)], microscale vein patterns and nanoscale dimples appear on crack surfaces. However, in the opposite case, the local quasi-cleavage/separation through local atomic clusters with local softening in the background ahead of the crack tip dominates, producing nanoscale periodic corrugations. At the atomic cluster level, energy dissipation in fracture of BMGs is, therefore, determined by two competing elementary processes, viz. conventional shear transformation zones (STZs) and envisioned tension transformation zones (TTZs) ahead of the crack tip. Finally, the mechanism for the formation of nanoscale periodic corrugation is quantitatively discussed by applying the present energy dissipation mechanism.