64 S. A. Turnage et al. Quasi-static compression from 10−3 to 1 s−1 is performed with a 5900 series Instron mechanical tester equipped with a furnace capable of reaching temperatures as high as 1473 K. Dynamic testing is performed using a Kolsky bar capable of reaching strain rates from 102 to 104 s−1 on such small specimens. A tube furnace capable of heating a sample to 1073 K is fitted to the Kolsky bar for high temperature testing. As the tube furnace also heats the ends of the Inconel Kolsky bar, a correction is applied in the form of ε = 4cTE(εi −εt ) ET + √E ∗ET ls σ = εt ETAb As where ε and σ are the engineering strain and stress in the specimen, cT and ET are the wavespeed and Young’s modulus of the bar at temperature, E is the Young’s modulus in the bar at room temperatrure, εi and εt are the measured strains in the incident and transmitted bars, ls is the specimen length, and Ab and As are the cross-sectional areas of the bar and specimen. Results As received material shows a high density of Ta nano-dispersions and a few twins throughout the material. The average Cu grain size is approximately 50 nm while Ta particles exist in a binary grouping of particle sizes. Ta nano-dispersions average 3.2 ±0.9 nm in diameter while larger Ta particles average 32 ±8 nm in diameter. The initial microstructure is shown in Fig. 11.1. (b) (a) Twins Nano-dispersions NC Cu -10 at.% Ta Fig. 11.1 Initial microstructure of NC-Cu-10 at.%Ta. (left) Precession diffraction image showing randomized texture of the alloy. (right) TEM images revealing (a) twins and (b) nano-dispersions in the as-extruded material
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