Micro- and Nano-Mechanical Behavior of Materials: Micro/Nano-Mechanics III
Program Organizers: Sundeep Mukherjee, University Of North Texas; Mahmoud Baniasadi, Georgia Southern University; Meysam Haghshenas, University of Toledo
Tuesday 2:00 PM
November 3, 2020
Room: Virtual Meeting Room 36
Location: MS&T Virtual
Session Chair: David Poerschke, University of Minnesota; Mahmoud Baniasadi, Georgia Southern University
2:00 PM Invited
Effects of Testing Temperature and Sample-size on Tensile Deformation of Metallic Glass: Golden Kumar1; 1The University of Texas at Dallas
Deformation of nanoscale metallic glasses has attracted increasing attention but remains controversial due to difficulty in fabrication and testing of small samples. Here, we report the effects of systematic variation in sample-size and testing temperature. Pt-based metallic glass samples with varying diameters (100 nm -500 m) were prepared by thermoplastic drawing. Multiple samples were deformed at different temperatures and the fracture morphologies were characterized using SEM. The results show that the fraction of vein-like morphology decreases with decreasing sample size and mirror-like fracture surface was observed in samples smaller than about 2 m in diameter. With further decreasing diameter, transition from shear-localized to necking was observed and the extent of neck increased with decreasing sample diameter. The lowering in temperature had similar effect as decrease in sample diameter. This temperature-size equivalence is discussed in terms of temperature rise and formation of liquid-like layer in shear bands.
2:20 PM Invited
Gradatim Ferociter: Exploring the Grain Size Stability of Heterogeneous Copper in Thermal, Mechanical and Radiation Environments
: Suveen Mathaudhu1; Heather Salvador1; Evander Ramos1; Sina Shahrezaei2; Khalid Hattar3; 1University of California, Riverside; 2Pacific Northwest National Laboratory; 3Sandia National Laboratories
Heterogeneous materials have been of recent interest due their enhanced mechanical response (namely, the excellent combinations of strength and ductility). Of less interest has been the stability of the gradient grain structures outside of ambient conditions, and there for a strong opportunity exists to explore the effects of temperature, mechanical load and radiation on the microstructural evolution in these unique systems. In this study, we will report our results on gradient heterogeneous copper produced by mechanical attrition in a SPEX mill, where the heterostructure is imparted by impacting media. Results on the stability after isochronal annealing, mechanical and wear properties, and radiation will be presented and compared with the current literature. These results will forecast the ability of heterostructured materials to be used in environments outside of static, ambient conditions.
2:40 PM
In Situ Nanomechanical Testing of Piezoresistive Materials: Steven Boles1; 1Hong Kong Polytechnic University
The ability to simultaneously probe the electrical properties of nanowires under tensile strain allows for new insights and understanding of material properties. Due to the low defect density in nanowires, these samples are often able to withstand extreme mechanical conditions beyond what is achievable with bulk counterparts. In this work, Ge and Te nanowires are used to probe fundamental relationships between their intrinsic resistivity and mechanical state. In both cases, tensile strain can be applied reliably and reversibly. By using a variety of electrical measurement conditions, a deeper understanding is gained regarding how the electronic band structure contributes to the conductivity of the wire. For the case of Ge, these results suggest that new, more efficient piezoresistive electronic devices can be realized. However, they also suggest that the ability to ever achieve a direct bandgap emission device from Ge may be extraordinarily difficult.