Nanostructuring of Metals, Alloys, and Composites
Nanostructured metal and alloy development represented a broad frontier in the materials science research in the last two decades. The fundamental research is based on the general assumption that material properties and deformation mechanisms strongly var
- PDF / 2,917,682 Bytes
- 58 Pages / 439.37 x 666.142 pts Page_size
- 41 Downloads / 287 Views
Nanostructuring of Metals, Alloys, and Composites
1.1
Introduction
Nanostructured materials are the most potential and exciting candidates in many fields for revolutionizing traditional material designs. Nanostructured metals and alloys are a class of materials exhibiting novel characteristics across a wide range of properties including increased hardness, superplasticity, and electrical conductivity (Schaefer 2010). Here, the difference between ultrafine and nanocrystalline metals needs a special mention. Conventionally, metals with a grain size in the range of 100–1000 nm are classified as ultrafine grain; grain sizes less than 100 nm are considered to be in the nanocrystalline domain (Gleiter 1989, 1993). The altered response of such properties is a direct consequence of the nanoscale microstructural arrangements of the atoms themselves (Murr 2015). Regarding engineering design, these metals pose significant promise as next-generation structural materials due to reported increases in ultimate strength, resistance to fatigue, and wear resistance (Mittemeijer 2010). Nanostructured materials represent a possible alternative for a broader range of applications, outperforming many of today’s engineering materials. As new nanomaterials are rapidly developing and many applications exist, mainly within fields such as medicine, communication, consumer goods, and engineering, it is necessary to identify what special properties this fairly new material group can offer. All engineering materials based on nanotechnology, involving the understanding of physical properties and how they change with material dimensions, are to be considered alternatives in existing products. Through following the Hall-Petch equation ky σ y ¼ σ 0 þ pffiffiffiffi D
© Springer Nature Switzerland AG 2021 P. Cavaliere, Fatigue and Fracture of Nanostructured Materials, https://doi.org/10.1007/978-3-030-58088-9_1
1
2
1 Nanostructuring of Metals, Alloys, and Composites
where σ y is the yield strength, σ 0 is a material constant (i.e., 25 for Cu, 70 for Fe, and 80 for Ti), ky represents the resistance of grain boundaries to dislocation mobility (transmission through grain boundaries) giving the quantification of the grain boundary strengthening (i.e., 0.11 for Cu, 0.74 for Fe, and 0.4 for Ti), and D is the mean grain size. A high density of grain boundaries limits the length of dislocation pileups and, due to restricted dislocation motion, extraordinarily high yield stress values can be observed (Gutkin and Ovid’ko 2004). However, the extraordinary mechanical properties of NC metals are limited by mechanisms related to the competing length scales (Anderson et al. 2014; Mohamed 2016). The Hall-Petch relationship essentially describes grain boundary strengthening, a process by which grain boundaries, or regions between crystallites of different lattice orientation, act as physical barriers for continued dislocation movement within the material (Armstrong 2014). For more traditional, course-grained materials consisting of average grain sizes ranging from 100 nm u
Data Loading...
