High temperature nano-indentation of tungsten: Modelling and experimental validation

Micromechanical and microstructural properties of tungsten fibers in the as-produced and annealed state: Assessment of the potassium doping effect

“…The x-axis on Fig.17(b) is reverted to enable easier comparison of the hardness at maximum depth (which will be referred as "saturated hardness", H 0 ). While the maximum indentation depth, d, is set as 1.4 µm (which is usual practice), the actual response of the material to the penetration of the indenter extends to the region of a factor of ~5 larger as it has been recently investigated by finite element analysis applied for tungsten [45]. Hence, we are exploring the response of the microstructure within the region of 5-7 µm underneath the indenter.…”

Hardness-Depth Relationship with Temperature Effect for Single Crystals—A Theoretical Analysis

“…For CaF 2 , H f is informed to be 1.2 GPa at room temperature [21], and vanishes to be zero around 473 K [34]. As to W, H f can be theoretically calculated by referring to Equation (5) with τ p0 = 1038 MPa, τ f0 = 2035 MPa, T 0 = 580 K, k B = 1.38 × 10 −23 J/K, H k = 1.65 × 10 −19 J,γ p0 = 3.71 × 10 10 s −1 andε = 0.02 s −1 [22,35]. Then, the experimental data can be plotted in the form asH 1/m n − 1/h for the four materials, as illustrated in Figure 2.…”

“…Based on the developed model, the effect of temperature on the evolution of different microstructures can be further analyzed, for example, the expansion of the plasticity affected region and evolution of dislocation density. Take W for an example, the temperature dependent shear modulus µ(T) and α(T) can be informed in previous works [35,38], and it is known that b = 0.274 nm and tan θ = 0.358 for the Berkovich nano-indentation of W [18,29], as summarized in Table 2. Therefore, according to Equation (9), one can calculate h * (T) and M(T) = 3 h * (T)/h * (T) at 160 K, 230 K and 300 K, respectively.…”

“…Figure 4 illustrates the evolution of h * (T) and M(T) as a function of T for single crystal W, which indicates that h * (T) decreases while M(T) increases with T. The former is rational as ρ S (T), determined by h * (T) as expressed in Equation (4), is considered to increase due to the high internal strain stored in the materials under high temperatures [25]. As a comparison, the latter is ascribed to the weakened impediment of slipping dislocations that the expansion of the plasticity affected region becomes comparatively easy at high temperatures [35]. Last but not the least, the evolution of ρ G (T) and ρ S (T) as a function of h at different temperatures is compared for single crystal W, as illustrated in Figure 5.…”

Effect of statistically stored dislocations in tungsten on the irradiation induced nano-hardening analyzed by different methods

“…At the same time, the investigation of the impact of high flux plasma exposure and high temperature annealing on W was also successfully studied by nanoindentation [22,23] . Some recent works have addressed the application of nanoindentation in combination with empirical and deterministic finite element modelling applied to W [24,25] .…”