Nonhydrostatic compression of gold powder to 60 GPa in a diamond anvil cell: estimation of compressive strength from x-ray diffraction data

et al. 2015

Phys. Rev. B

Series of high-pressure x-ray diffraction patterns of iron and its high-pressure polymorphs were collected with 0.1-0.2-s exposure time utilizing a membrane diamond anvil cell (DAC) for compression at various loading and unloading rates to a maximum pressure of 70 GPa. Strain rates of 10 −2 s −1 at a maximum pressurization rate of 4.1 GPa/s were achieved in non-hydrostatic compression of hcp Fe. Linewidth analysis was used to retrieve strain and uniaxial stress of Fe as a function of pressure upon both compression and decompression. Analysis of the lattice parameters ratio c/a of hcp Fe indicates the presence of complex non-hydrostatic stress states, which developed as a function of strain rate, relaxation time, and various levels of hydrostaticity. Our results emphasize the importance of a controlled pressurization in DACs because the experimental loading rate strongly influences the stress state of the sample, particularly on decompression. Our time-resolved x-ray diffraction of the phase transition from bcc Fe to hcp Fe reveals residual grains of bcc Fe capable of surviving to very high pressures (>35 GPa) for a few minutes after the transition.

Section: Discussionsupporting

confidence: 57%

In situx-ray diffraction of fast compressed iron: Analysis of strains and stress under non-hydrostatic pressure

Konôpková¹,

Rothkirch²,

et al. 2015

Phys. Rev. B

“…The diffraction-line broadening has been used to determine the maximum stress in the stress distribution in the crystallites. [2][3][4][5][6][7][8][9][10][11][12] The maximum stress p max (ffi eY, where e and Y are the micro-strain and the aggregate Young's modulus, respectively) is often termed the micro-differential stress (micro-DS) and is taken as the measure of compressive strength of the polycrystalline sample material. Some studies used p max (e.g., Refs.…”

Section: Introductionmentioning

confidence: 99%

“…2 and 5-7), whereas others 2p max (e.g., Refs. [8][9][10][11][12] as the measure of micro-DS. The macro-stresses at the center of the sample compressed in a DAC possess a cylindrical symmetry about the load axis, the axial stress component r 33 being larger than the radial stress component r 11 .…”

Section: Introductionmentioning

confidence: 99%

Strength of polycrystalline niobium from high-pressure x-ray diffraction data: A comparison of results from line-width and line-shift analyses

Journal of Applied Physics

Liermann

2015

High purity polycrystalline niobium was compressed in a diamond anvil cell (DAC) without any pressure transmitting medium and the pressure was increased in steps of ∼5 GPa to the highest pressure of ∼40 GPa. The diffraction pattern was recorded after each pressure increment using angle-dispersive mode with the conventional diffraction geometry, wherein the primary x-ray beam is parallel to the load axis of the DAC. The strength of niobium as function of pressure was determined using the line-width and line-shift analyses. Both eY and 2eY, where Y is the aggregate Young's modulus and e is the strain determined from the line-width analysis, have been used as the measure of strength in earlier studies. In this study, it is eY that agrees with the strength determined from the line-shift analysis of the radial diffraction data as well as the data from the conventional diffraction geometry. These results have been discussed and compared with a similar observation made earlier on strength of diamond. This study highlights the ambiguity that presently exists in choosing eY or 2eY as a measure of strength while attempting to estimate the strength from the diffraction line width analysis.

“…The values of C ij (0) and C 0 ij ð0Þ for silver were taken from the measurements by Daniels and Smith [25]. The earlier studies have shown that 2p max is a measure of compressive strength in agreement with the strength derived from the shifts of the diffraction lines [11,14].…”

Section: Methods Of Data Analysismentioning

confidence: 86%

“…The micro-stresses vary randomly in direction and magnitude in each crystallite [3], and produce micro-strains that cause the diffraction lines to broaden. The product of micro-strain and an appropriate Young's modulus is a measure of the compressive yield strength of the solid sample [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. It may be mentioned that the X-ray diffraction measures lattice strains that are elastic even though the sample undergoes considerable plastic deformation during pressurization.…”

Section: Introductionmentioning

confidence: 99%

Compression of silver in a diamond anvil cell: Pressure dependences of strength and grain size from X-ray diffraction data

Liermann

Jain

Journal of Physics and Chemistry of Solids

et al. 2010

a b s t r a c tTwo silver samples, coarse grained (c-Ag, grain size 300 7 30 nm) and nanocrystalline (n-Ag, grain size 557 6 nm), are compressed in a diamond anvil cell in separate experiments. The pressure is increased in steps of $ 3 GPa and the diffraction pattern recorded at each pressure. The grain size and compressive strength are determined from the analysis of the diffraction line-widths. The grain size of c-Ag decreases rapidly from 300 7 30 nm at ambient pressure to 40 7 8 nm at 15 GPa, and then gradually to 20 7 3 nm at 40 GPa. After pressure release to ambient condition, the grain size is 25 7 4 nm. The strength at ambient pressure is 0.18 70.05 GPa and increases to 1.07 0.3 GPa at 40 GPa. The grain size of n-Ag decreases from 55 7 6 nm at ambient pressure to 17 7 4 nm at 15 GPa and to 14 7 3 nm at 55 GPa. After release of pressure to ambient condition, the grain size is 50 7 7 nm. The strength increases from 0.51 70.07 GPa at ambient pressure to 3.5 7 0.4 GPa at 55 GPa. The strength is found to vary as the inverse of the square-root of the grain size. The results of the present measurements agree well with the grain-size dependence of strength derived from the hardness versus grain size data at ambient pressure available in the literature.