Microstructure‐based finite element modeling was performed on different microstructures of an austenitic‐ferritic cast duplex stainless steel using the constitutive behavior of individual phase ...obtained from micropillar compression tests. A qualitative analysis of equivalent plastic strain and von Mises stress was conducted in plane stress and plane strain conditions. The simulated results reveal that the morphology and the area fraction of the second phase can affect the mechanical properties. The stress values and the equivalent plastic strain in the shear bands are higher in plane strain loading than plane stress loading condition. Stress is concentrated mostly in ferrite phase. The evolution of stress during deformation is found to be dependent on the morphologies of ferrite phase in austenite matrix.
Microstructure‐based finite element modeling has been performed on different microstructures of an austenitic‐ferritic stainless steel using the constitutive behavior of individual phase obtained from micropillar compression tests. The simulated plastic strain and stress distribution reveal the effect of area fraction, morphology as well as the distribution of ferrite phase on the mechanical properties of the material.
The effect of prior deformation on mechanical behavior as a function of size is investigated for body-centered cubic (bcc) molybdenum (Mo) pillars. Experiments were performed using focused ion beam ...(FIB) manufactured 0 0 1 and 2 3 5 Mo micro/nanopillars, which were compressed, re-FIB machined, and compressed again. Unlike in bulk materials, pre-straining has a negligible effect on stress-strain behavior of the pillars, suggesting that dislocation storage does not occur in small-scale bcc specimens. The prevailing mechanism behind the size effect is attributed to dislocation nucleation mechanisms.
Herein, we report on mechanical deformation of single-crystal Ti2AlC MAX phase using compression testing of micropillars with a range of crystallographic orientations. Our results show that depending ...on the crystallographic orientation, the Ti2AlC micropillars either undergo only non-classical (non-Schmid) crystallographic slip, non-classical crystallographic slip followed by cleavage or cleavage without any appreciable crystallographic slip. The non-classical crystallographic slip is found to be a result of the strong dependence of crystallographic slip on both, the resolved shear stress and the stress normal to the slip plane.
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•Measurement of silicon segregation in solution strengthened ferritic ductile iron.•Micropillar compression tests and trace analysis.•Determination of CRSS as a function of the ...silicon content in the ferrite matrix.•Comparison of the measured CRSS with macroscopic yield limits under tension and compression.
Solid solution strengthened ferritic ductile iron (SSFDI) exhibits improved mechanical properties compared to conventional ductile cast iron (DCI) grades, however, its potential widespread application is hindered by unpredictable brittle fracture which might be attributed to microstructural silicon segregation and associated superstructure formation. The aim of the present study is therefore to deepen the understanding on the effect of local silicon segregation on the mechanical properties of SSFDI, which is crucial especially for the common applications of DCI in cyclically loaded structures. Micropillar compression tests were carried out on three different casts to investigate the solution strengthening effect of silicon in the ferritic matrix. An almost perfect linear relationship between critical resolved shear stress (CRSS) and global silicon content was found. It was also found that the variation of CRSS with silicon content corresponds well to the variation of the macroscopic yield limits (under tension and compression) with global silicon content of different SSFDI alloys. This indicates that the ferritic matrix dominates the yield limit of the DCI alloys investigated in this study, while the morphology of the graphite nodules plays a minor role under monotonic loading conditions.
Herein, we report on mechanical deformation of single-crystal Ti
2
AlC MAX phase using compression testing of micropillars with a range of crystallographic orientations. Our results show that ...depending on the crystallographic orientation, the Ti
2
AlC micropillars either undergo only non-classical (non-Schmid) crystallographic slip, non-classical crystallographic slip followed by cleavage or cleavage without any appreciable crystallographic slip. The non-classical crystallographic slip is found to be a result of the strong dependence of crystallographic slip on both, the resolved shear stress and the stress normal to the slip plane.
This work elucidates single-crystal level non-classical deformation mechanism(s) of a MAX phase and unravels the observed extreme plastic anisotropy of MAX phases.
For 3D IC application, The thickness of micro joint is basically smaller than that in the conventional joint. IMCs can easily occupy micro joints during assembling or operation and then dominate the ...properties of micro joint. It is predicted that IMCs are going to be utilized as structural materials in near submicron-scale micro joint in these few years. The micromechanical behavior of IMCs is the important criterion to evaluate the suitability of IMCs as structural material in micro joints. In this study, the micromechanical behaviors of single crystalline IMCs generally formed in micro joints was conducted by micropillar compression. The failure mode of single-crystalline Cu6Sn5 and Ni3Sn4 are cleavage, however, the in-situ images and cross-section view showed that both Cu6Sn5 and Ni3Sn4 still preformed plastic deformation before failure, however, both Cu6Sn5 and Ni3Sn4 somehow plastically deformed through slip along the certain crystallographic direction on certain crystallographic planes. Most importantly, Ni3Sn4 can withstand a large amount of plastic deformation strain by compression which is more than 4 % in certain orientation. In comparison of these two IMCs, Ni3Sn4 showed the better mechanical performance including yield strength, strain to yield, failure strength, strain to failure and Young's modulus than Cu6Sn5. Thus, Ni3Sn4 has higher toughness and should be more promising to use as structure materials of 3D IC micro joints.
For 3D IC application, solder volume in micro joint is much smaller than in the conventional joint. IMCs can easily occupied micro joints and dominate the properties of micro joint. Thus, it is ...anticipated that IMCs are to be used as structural materials in commercial scale in a few years. However, mechanical property data for reliability modelling are lacking. To characterize mechanical properties of IMCs becomes an urgent issue. In this study, we investigated the micromechanical behaviors of single crystalline IMCs generally formed in micro joints. Testing structures were produced by focused ion beam machining and subsequently tested by picoindenter in SEM which can simultaneously observe the sequence of failure of test structure. Our results are helpful on understanding the fracture modelling of IMCs.
Owing to excellent mechanical properties, beryllium‑aluminum (BeAl) alloys have garnered significant attentions as advanced structural materials in the military sector. However, they also suffer from ...extremely low solubility between Be and Al, and a lack of effective techniques for large-scale BeAl alloy fabrication. In this study, Be-Al-Ag-Si alloys were fabricated with significantly refined microstructures and improved micro-mechanical properties by incorporating additional Ag and Si elements and utilizing electron beam welding (EBW) technique. Micropillar compression results indicate that the yield strength (YS) of the fusion zone (FZ) in the as-welded Be-Al-Ag-Si alloys is approximately 540 MPa, which is around 135% higher than that of the substrate zone (SZ) with YS of approximately 230 MPa. The significant improvement can be mainly attributed to the grain boundary strengthening and dislocation strengthening due to the rapid heating/cooling rate and high thermal residual stress in the FZ, as revealed by microstructural analysis. Additionally, other strengthening mechanisms, such as Orowan and GP zone strengthening, could also make a contribution. These results offer further understanding towards the production of large-scale BeAl alloys with improved flow ability and mechanical properties.
•Be-Al alloys with refined microstructures and improved micro-mechanical properties through additions of Ag and Si.•Compared to grain size of the substrate zone, grain size in the fusion zone are refined approximately 20 times.•The micro-mechanical properties of the fusion zone are increased by about 135% higher than that of the substrate zone.•Enhancement of micro-mechanical properties is mainly attributed to the grain boundary and dislocation strengthening.
Bulk‐scale (2¯$\bar{2}$01)‐oriented monoclinic beta‐phase gallium oxide (β‐Ga2O3) single crystals are brittle and fracture at low compressive strains. Here, it is reported that submicron β‐Ga2O3 ...pillars exhibit an exceptional room temperature plastic strain of up to ≈22% under compression. Deformation is observed in transition from brittle to superior plasticity with reduction of pillar size. The critical diameter for the brittle to ductile transition is ≈800 nm, attributed to the initiation of dislocation slip on the primary (400) slip planes. Below 500 nm, a second transition is reported to superior plastic deformation, achieved through the activation of secondary mechanisms due to both deconfinement and low crystalline symmetry of β‐Ga2O3, differentiating this finding from size‐effected plasticity of other brittle materials where plasticity is attributed to dislocation slip on primary slip planes. Molecular dynamics simulation supports the proposed mechanism of pillar deconfinement where plastic deformation in larger pillars is solely dominated by planar defects on (400) slip planes, while secondary defects are induced for sufficiently small pillars. No plasticity is observed for equally dimensioned pillars tested on a (010)‐oriented surface, highlighting the importance of presenting crystallography on submicron plasticity in this material.
Superior plasticity of monoclinic beta‐phase gallium oxide β‐Ga2O3 single crystals is observed for micropillar diameters <500 nm due to lateral deconfinement and low crystal symmetry. The ultra‐high plasticity of this eminently brittle material is desirable for flexible electronic device applications. The observed superior plasticity opens opportunities to further study and leverage semiconductors with low symmetry crystal structures.
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