The last few decades have seen a rapid development of techniques to measure material properties at small length-scales, such as thermal analysis at the nano-scale [1], micro/nano-mechanical testing [2], even functional properties of specific microstructural features [3]. However, deformation processing of materials has received much less attention at small length-scales: mainly only work-free processes – e.g. thermal – have been carried out in situ in electron microscopes. Indeed, few bulk deformation processing methods are adaptable at the micron or nano-scale, due to the need for complex tooling – e.g. rollers or extrusion dies. However, forging at the micron scale may be considered, even multi-axially, across a range of temperatures (-150 – 700 °C currently) and deformation schedules (monotonic or fatigue). Such multi-axial micro-forging is demonstrated here on a micron-scale cube of lamellar γ-TiAl alloy as a method to engineer, in a targeted manner, a hierarchically nanotwinned microstructure. Compared to regular lamellar γ-TiAl, this approach aims to reduce the strength anisotropy measured in subsequent micromechanical tests, which is normally thought to be the cause of poor inter-grain compatibility, and hence a low ductility of such alloys.
[1] King, W. P., Saxena, S., Nelson, B. A., Weeks, B. L. & Pitchimani, R. Nanoscale thermal analysis of an energetic material. Nano Letters 6, 2145-2149, (2006).
[2] Dehm, G., Jaya, B. N., Raghavan, R. & Kirchlechner, C. Overview on micro- and nanomechanical testing: New insights in interface plasticity and fracture at small length scales. Acta Materialia 142, 248-282, (2018).
[3] Bishara, H., Lee, S., Brink, T., Ghidelli, M. & Dehm, G. Understanding grain boundary electrical resistivity in Cu: the effect of boundary structure. ACS Nano, (2021).
| Subject : | : | oral |
| Topics | : | 4-1 - Experimental Micromechanics and Nanomechanics |
| PDF version | : |  PDF version |
