The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
E Nembach - One of the best experts on this subject based on the ideXlab platform.
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the effects of the degree of randomness of arrays of Shearable particles on the critical Resolved Shear Stress of particle strengthened materials
Acta Materialia, 2004Co-Authors: T Pretorius, E NembachAbstract:Abstract It has been investigated in computer simulations how the randomness ( ≙ irregularity) of the arrangement of particles in the glide plane affects the critical Resolved Shear Stress (CRSS) of materials strengthened by Shearable nano-scale particles. The result is that there is an overall increase of the CRSS with increasing degree of randomness, that is with decreasing regularity, but this increase is not monotonic.
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on the temperature dependence of the critical Resolved Shear Stress of the γ strengthened superalloy nimonic pe16
Scripta Materialia, 2002Co-Authors: Angelika Vennemann, Eckhard Langmaack, E NembachAbstract:Abstract The temperature dependence of γ ′ -strengthening of the commercial nickel-base superalloy NIMONIC PE16 has been investigated by measuring the critical Resolved Shear Stress in the temperature range 373–1173 K and observing the resulting slip line patterns.
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quantitative representation of the anisotropy and tension compression asymmetry of the critical Resolved Shear Stress of an l12 ordered intermetallic
Intermetallics, 1999Co-Authors: E Nembach, Astrid NitzAbstract:Abstract The anomalous anisotropy and tension (t)/compression (c)-asymmetry of the critical Resolved Shear Stress τo of the L12-long-range ordered intermetallic γ′NIM are analysed in the light of a published (Miner RV, Gabb TP, Gayda J, Hember, KJ. Met Trans A 1986; 17A: 507) analytical expression τ o hkl ,t/c,T o ⩽T⩽T peak . Particles of γ′NIM strengthen the commercial nickel-base superalloy NIMONIC 105. hkl characterises the orientation of the specimen, and To≈300 K and Tpeak≈ 1000 K mark the temperature (T) range in which τo is anomalous. Except for γ′NIM-single crystals with the [011]-orientation, the formula describes the anisotropy and (t/c)-asymmetry of the critical Resolved Shear Stress satisfactorily.
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critical Resolved Shear Stress anomalies of the l12 long range ordered γ phase of the superalloy nimonic 105
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 1999Co-Authors: Astrid Nitz, E NembachAbstract:Abstract The critical Resolved Shear Stress τ 0NIM γ ′ of the multicomponent nickel-rich L1 2 -long-range ordered γ′ -phase γ′ NIM has been measured in tension (t) and compression (c) tests. Precipitates of γ′ NIM strengthen the commercial nickel-base superalloy NIMONIC 105. The nominal orientations hk l of the single crystal axes were: [001], [011], 1 11 , and 1 23 ; the deformation temperatures ( T ) ranged from 283 to 1150 K. The results τ 0NIM γ ′ ( hk l , T , t / c ) show the following anomalies: 1) positive slope ∂τ 0 γ′ ∂T , 2) anisotropy; 3) t / c -asymmetry. The experimental data τ 0NIM γ ′ ( hk l , T , t / c ) are discussed in the light of current models.
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the critical Resolved Shear Stress of peak aged aluminium lithium single crystals
Acta Materialia, 1999Co-Authors: Avraam Kalogeridis, Josef Pesicka, E NembachAbstract:Abstract The critical Resolved Shear Stress (CRSS) of single crystals of aluminium-rich aluminium–lithium alloys has been measured at 283 K. These alloys are strengthened by coherent precipitates of the metastable L1 2 long-range-ordered δ ′ phase. The specimens had been subjected to long aging treatments such that they were in the peak-aged state. This contrasts with the earlier investigation (Schlesier and Nembach, Acta metall. mater. , 1995, 43 , 3983) in which underaged Al–Li single crystals have been studied. The contribution τ p of the δ ′ precipitates to the present peak-aged specimens' total CRSS has been found to be a function only of the δ ′ volume fraction f , i.e. τ p was independent of the radius of the δ ′ precipitates. The experimental data τ p ( f ) are well represented by a relation which had been developed for the description of peak-aged γ ′-strengthened nickel-base superalloys. These latter materials are isomorphous to δ ′-strengthened Al-rich Al–Li alloys: coherent L1 2 long-range-ordered particles are embedded in a disordered f.c.c. matrix.
Jingya Wang - One of the best experts on this subject based on the ideXlab platform.
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effect of al content on the critical Resolved Shear Stress for twin nucleation and growth in mg alloys
arXiv: Materials Science, 2020Co-Authors: Jingya Wang, J M Molinaaldareguia, Javier LlorcaAbstract:The effect of Al atoms in solid solution on the critical Resolved Shear Stress for twin nucleation and growth was analyzed by means of the combination of diffusion couples with compression tests in micropillars oriented for twinning. The critical Resolved Shear Stress for twin nucleation was higher than that for twin growth and both increased by the same amount with the Al content. Nevertheless, the increase was small ( approx. 10 MPa) for 4 at.%Al but large (up to 60-70 MPa) for 9 at.%Al. These results were in agreement with Labusch-models based on first principles calculations in the dilute regime (< 5 at.%Al) [51]. Comparison with recent data in the literature showed that Al atoms are more effective in increasing the critical Resolved Shear Stresses for twin nucleation and growth than for basal slip [21]. Finally, compression tests in micropillars oriented along [0001] showed the critical Shear Stress for pyramidal slip increased rapidly with the Al content from 98 MPa in pure Mg to 250 MPa in Mg-9 at.%Al. Thus, the addition of Al increased the plastic anisotropy of Mg alloys.
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Effect of Al content on the critical Resolved Shear Stress for twin nucleation and growth in Mg alloys
Acta Materialia, 2020Co-Authors: Jingya Wang, Jon M. Molina-aldareguia, Javier LlorcaAbstract:Abstract The effect of Al atoms in solid solution on the critical Resolved Shear Stress for twin nucleation and growth was analyzed by means of the combination of diffusion couples with compression tests in micropillars oriented for twinning. The critical Resolved Shear Stress for twin nucleation was higher than that for twin growth and both increased by the same amount with the Al content. Nevertheless, the increase was small (≈ 10 MPa) for 4 at%Al but large (up to 60–70 MPa) for 9 at%Al. These results were in agreement with Labusch-models based on first principles calculations in the dilute regime (
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effect of solute content and temperature on the deformation mechanisms and critical Resolved Shear Stress in mg al and mg zn alloys
arXiv: Materials Science, 2019Co-Authors: Jingya Wang, Rouhollah Alizadeh, Miguel A. Monclús, Nan Li, J M MolinaaldareguiaAbstract:The influence of solute atoms (Al and Zn) on the deformation mechanisms and the critical Resolved Shear Stress for basal slip in Mg alloys at 298 K and 373 K was ascertained by micropillar compression tests in combination with high-throughput processing techniques based on the diffusion couples. It was found that the presence of solute atoms enhances the size effect at 298 K as well as the localization of deformation in slip bands, which is associated with large strain bursts in the Resolved Shear Stress ($\tau_{RSS}$)-strain ($\epsilon$) curves. Deformation in pure Mg and Mg alloys was more homogeneous at 373 K and the influence of the micropillar size on the critical Resolved Shear Stress was much smaller. In this latter case, it was possible to determine the effect of solute content on the critical Resolved Shear Stress for basal slip in Mg-Al and Mg-Zn alloys.
Javier Llorca - One of the best experts on this subject based on the ideXlab platform.
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effect of al content on the critical Resolved Shear Stress for twin nucleation and growth in mg alloys
arXiv: Materials Science, 2020Co-Authors: Jingya Wang, J M Molinaaldareguia, Javier LlorcaAbstract:The effect of Al atoms in solid solution on the critical Resolved Shear Stress for twin nucleation and growth was analyzed by means of the combination of diffusion couples with compression tests in micropillars oriented for twinning. The critical Resolved Shear Stress for twin nucleation was higher than that for twin growth and both increased by the same amount with the Al content. Nevertheless, the increase was small ( approx. 10 MPa) for 4 at.%Al but large (up to 60-70 MPa) for 9 at.%Al. These results were in agreement with Labusch-models based on first principles calculations in the dilute regime (< 5 at.%Al) [51]. Comparison with recent data in the literature showed that Al atoms are more effective in increasing the critical Resolved Shear Stresses for twin nucleation and growth than for basal slip [21]. Finally, compression tests in micropillars oriented along [0001] showed the critical Shear Stress for pyramidal slip increased rapidly with the Al content from 98 MPa in pure Mg to 250 MPa in Mg-9 at.%Al. Thus, the addition of Al increased the plastic anisotropy of Mg alloys.
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Effect of Al content on the critical Resolved Shear Stress for twin nucleation and growth in Mg alloys
Acta Materialia, 2020Co-Authors: Jingya Wang, Jon M. Molina-aldareguia, Javier LlorcaAbstract:Abstract The effect of Al atoms in solid solution on the critical Resolved Shear Stress for twin nucleation and growth was analyzed by means of the combination of diffusion couples with compression tests in micropillars oriented for twinning. The critical Resolved Shear Stress for twin nucleation was higher than that for twin growth and both increased by the same amount with the Al content. Nevertheless, the increase was small (≈ 10 MPa) for 4 at%Al but large (up to 60–70 MPa) for 9 at%Al. These results were in agreement with Labusch-models based on first principles calculations in the dilute regime (
D. Chidambarrao - One of the best experts on this subject based on the ideXlab platform.
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Effect of crystallographic alignment of isolation trenches: A Resolved‐Shear‐Stress perspective
Applied Physics Letters, 1992Co-Authors: D. ChidambarraoAbstract:We have analyzed and compared the Resolved Shear Stresses of all 12 glide systems for the 60° dislocation for 〈110〉‐aligned and 〈100〉‐aligned isolation trenches. From among the 12 glide systems, we select for each trench alignment the one which exhibits the highest Stress level. The results for the two alignments are then compared. We find that the largest Resolved Shear Stress for a 〈110〉‐oriented trench is about 30% more than that for a 〈100〉‐oriented trench from both the isotropic and the anisotropic analyses. Other factors that may cause a reduction of dislocation density for the 〈100〉‐trench alignment are also discussed.
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effect of crystallographic alignment of isolation trenches a Resolved Shear Stress perspective
Applied Physics Letters, 1992Co-Authors: D. ChidambarraoAbstract:We have analyzed and compared the Resolved Shear Stresses of all 12 glide systems for the 60° dislocation for 〈110〉‐aligned and 〈100〉‐aligned isolation trenches. From among the 12 glide systems, we select for each trench alignment the one which exhibits the highest Stress level. The results for the two alignments are then compared. We find that the largest Resolved Shear Stress for a 〈110〉‐oriented trench is about 30% more than that for a 〈100〉‐oriented trench from both the isotropic and the anisotropic analyses. Other factors that may cause a reduction of dislocation density for the 〈100〉‐trench alignment are also discussed.
Astrid Nitz - One of the best experts on this subject based on the ideXlab platform.
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quantitative representation of the anisotropy and tension compression asymmetry of the critical Resolved Shear Stress of an l12 ordered intermetallic
Intermetallics, 1999Co-Authors: E Nembach, Astrid NitzAbstract:Abstract The anomalous anisotropy and tension (t)/compression (c)-asymmetry of the critical Resolved Shear Stress τo of the L12-long-range ordered intermetallic γ′NIM are analysed in the light of a published (Miner RV, Gabb TP, Gayda J, Hember, KJ. Met Trans A 1986; 17A: 507) analytical expression τ o hkl ,t/c,T o ⩽T⩽T peak . Particles of γ′NIM strengthen the commercial nickel-base superalloy NIMONIC 105. hkl characterises the orientation of the specimen, and To≈300 K and Tpeak≈ 1000 K mark the temperature (T) range in which τo is anomalous. Except for γ′NIM-single crystals with the [011]-orientation, the formula describes the anisotropy and (t/c)-asymmetry of the critical Resolved Shear Stress satisfactorily.
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critical Resolved Shear Stress anomalies of the l12 long range ordered γ phase of the superalloy nimonic 105
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 1999Co-Authors: Astrid Nitz, E NembachAbstract:Abstract The critical Resolved Shear Stress τ 0NIM γ ′ of the multicomponent nickel-rich L1 2 -long-range ordered γ′ -phase γ′ NIM has been measured in tension (t) and compression (c) tests. Precipitates of γ′ NIM strengthen the commercial nickel-base superalloy NIMONIC 105. The nominal orientations hk l of the single crystal axes were: [001], [011], 1 11 , and 1 23 ; the deformation temperatures ( T ) ranged from 283 to 1150 K. The results τ 0NIM γ ′ ( hk l , T , t / c ) show the following anomalies: 1) positive slope ∂τ 0 γ′ ∂T , 2) anisotropy; 3) t / c -asymmetry. The experimental data τ 0NIM γ ′ ( hk l , T , t / c ) are discussed in the light of current models.
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the critical Resolved Shear Stress of a superalloy as a combination of those of its γ matrix and γ precipitates
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 1998Co-Authors: Astrid Nitz, E NembachAbstract:The critical Resolved Shear Stress (CRSS), τ 0, of peak-aged single crystals of the γ′-hardened commercial nickel-base superalloy NIMONIC 105 has been measured as a function of temperature T and orientation [hkl] of the compression axis. The same measurements have been carried out for the two constituent phases of NIMONIC 105: for the single-phase γ matrix and for the single-phase L12-long-range ordered γ′ phase. The value of T ranged from 283 to 1150 K, and the following orientations were studied: [001], [011], $$[\bar 111]$$ , and $$[\bar 123]$$ . The specimens were compression tested. The τ 0 values of NIMONIC 105 and of the γ′ phase are anisotropic; the anisotropy of NIMONIC 105 is similar to that of the γ′ phase, but less pronounced. The τ 0 of the γ phase is isotropic. The τ 0 values of the γ and of the γ′ phase vary with T, whereas the τ 0 of NIMONIC 105 is nearly independent of T for 400 K≤T≤1000 K. A model is presented that relates the function τ 0 ([h, k, l], T) of NIMONIC 105 to the analogous functions of its constituent γ and γ′ phase.