Lower Yield Stress Research Articles

Development of Low-Yield Stress Co\u2013Cr\u2013W\u2013Ni Alloy by Adding 6 Mass Pct Mn for Balloon-Expandable Stents

This is the first report presenting the development of a Co–Cr–W–Ni–Mn alloy by adding 6 mass pct Mn to ASTM F90 Co–20Cr–15W–10Ni (CCWN, mass pct) alloy for use as balloon-expandable stents with an excellent balance of mechanical properties and corrosion resistance. The effects of Mn addition on the microstructures as well as the mechanical and corrosion properties were investigated after hot forging, solution treatment, swaging, and static recrystallization. The Mn-added alloy with a grain size of ~ 20 µm (recrystallization condition: 1523 K, 150 seconds) exhibited an ultimate tensile strength of 1131 MPa, 0.2 pct proof stress of 535 MPa, and plastic elongation of 66 pct. Additionally, it exhibited higher ductility and lower yield stress while maintaining high strength compared to the ASTM F90 CCWN alloy. The formation of intersecting stacking faults was suppressed by increasing the stacking fault energy (SFE) with Mn addition, resulting in a lower yield stress. The low-yield stress is effective in suppressing stent recoil. In addition, strain-induced martensitic transformation during plastic deformation was suppressed by increasing the SFE, thereby improving the ductility. The Mn-added alloys also exhibited good corrosion resistance, similar to the ASTM F90 CCWN alloy. Mn-added Co–Cr–W–Ni alloys are suitable for use as balloon-expandable stents.

Effect of Dispersion Solvents and Ionomers on the Rheology of Catalyst Inks and Catalyst Layer Structure for Proton Exchange Membrane Fuel Cells.

This study investigated the effects of the dielectric constant (ε) of a dispersion solvent and ionomer content on the rheology of graphitized carbon (GC)-supported Pt catalyst ink and the structure of catalyst layers (CLs). The ionomer dispersions and catalyst inks were tested using rheological techniques, zeta (ξ) potential, and dynamic light scattering measurements. Results showed that increases in the solvent ε or ionomer content increased the ξ-potential of catalyst particles in the ink, which reduced the catalyst agglomerate size. Steady-state and oscillation scans showed that the Pt/GC catalyst ink had shear-thinning properties and gel-like behavior. The ink with a solvent ε of 40 tended to be more Newtonian fluid, with low yield stress (σy). The ionomer content altered the rheology of the ink by changing the internal interaction of inks. Solvents with ε of 70 and 55 enhanced the adsorption of ionomers onto catalysts, thereby increasing the adhesion between ink particles and reducing the risk of CL cracking. As the ionomer content increased, the catalyst absorbed more ionomers in inks, increasing the fracture toughness of CLs, which reduced the crack width.

Usability of mortar for predicting shear strength development at rest of fresh self compacting concrete

Determining the relationship between the rheological parameters of the model mortar and the rheological parameters of SCC (Self-Compacting Concrete) was the aim of the work. The static yield stress and the thixotropy coefficient AT were determined, which are important due to the development of the shear strength at rest and the formwork pressure generated during SCC casting. Shear strength of SCC reflected as static yield stress gs at rest develops mainly due to a self-compaction ability of SCC. And in the longer term, gs develops due to the progressive hydration of the cement and the disappearance of the HRWR impact (loss of fluidity). The static yield stress gs depends on w/c ratio, the type of HRWR (High Range Water Reducers) and cement. SCCs with a higher w/c ratio develop static yield stress gs faster, but up to 40 min the influence of w/c ratio decreases. The stiffening of SCC due to thixotropy increases the shear strength of SCC, but at the same time, it slows down the self-compaction of concrete. Thixotropy coefficient AT depends primarily on w/c ratio, and with the same w/c, on the type of cement and HRWR. The thixotropy coefficient AT increases in the initial period of SCC being at rest. The SCC with higher w/c ratio are characterized by higher thixotropy coefficient AT but at the same time by lower static yield stress gs. The significance of the thixotropic effect for shear strength disappears in time.

Microstructures and Mechanical Properties of Equiatomic NiTi Shape Memory Alloy Undergoing Local Canning Compression and Subsequent Annealing

Local canning compression is imposed on equiatomic NiTi shape memory alloy (SMA) with complete B19′ martensite. A fraction of retained nanocrytalline grains are embedded in the dominant amorphous phase. The compressed NiTi samples are annealed for 2 h at various temperatures, including 300, 450 and 600 °C. Grain size increases with increasing crystallization temperature during heat treatment. Under annealing at 300 °C, nanocrystalline grains are dominant in NiTi SMA, where there exists local amorphous zone. Under annealing at 450 °C, almost complete nanocrystalline can be obtained. Under annealing at 600 °C, grain size increases substantially, but there still exists a small amount of nanocrystalline grains. Under annealing at 300 °C, NiTi SMA exhibits extremely high elastic limit, but its plasticity is poor. Under annealing at 450 °C, NiTi SMA exhibits very high yield stress and it simultaneously keeps high plasticity. Under annealing at 600 °C, NiTi SMA exhibits relatively low yield stress, but its yield stress is still higher than that of as-received NiTi SMA and its plasticity is also high.

Effect of Hydrothermal Dehydration on the Slurry Ability of Lignite.

The high moisture content limits the large-scale utilization of lignite. Hydrothermal dehydration (HTD) has been confirmed as an effective method to improve the quality of lignite for further utilization. In this study, the effects of the changes in the lignite interface properties caused by the HTD modified final temperature on the slurry ability were investigated in the range of 160–200 °C. The results indicated that with the gradual rise of the HTD modified final temperature, the content of the carboxyl groups and phenolic hydroxyl groups on the surface of lignite decreased by 21.95 and 36.34%, respectively. In the meantime, the atomic ratio of oxygen/carbon, the content of equilibrium moisture, and the thickness of the hydrated film were reduced from 0.293, 14.63%, and 34.26 nm to 0.252, 9.43%, and 13.33 nm, respectively. Therefore, these changes of interfacial properties improved the slurry ability of lignite, with higher fixed-viscosity solid concentration, lower yield stress, increased pseudo-plasticity, and gradually decreased static stability of the prepared lignite coal water slurry. hydrothermal dehydration; slurry ability; oxygen-containing functional groups; hydrated film

Why do continental normal fault earthquakes have smaller maximum magnitudes?

Continental normal fault earthquakes have been reported to have smaller maximum magnitudes (Mmax) than continental earthquakes with other fault geometries. This difference has significant implications for understanding seismic hazards in extensional regions. Using the Global Centroid Moment Tensor (GCMT) catalog, we examine how Mmax varies with fault geometry in continental regions, whether these trends are robust, and potential physical reasons for the smaller magnitudes of continental normal fault earthquakes.We find that the largest continental normal fault earthquakes are in the low Mw 7 range whereas other fault geometries can reach ~Mw 8. The continental normal fault earthquake magnitude-frequency distribution has a lower corner magnitude (a parameterization of Mmax) than other fault geometries. The observed smaller continental normal fault Mmax is not an artifact of classification criteria or catalog length. Probability calculations indicate that the GCMT catalog is long enough to capture differences in Mmax due to fault geometry. Additionally, our analysis indicates that neither fault length nor width is limiting the size of continental normal fault earthquakes. Fault complexity can limit rupture extent, but it is likely not the primary reason for the smaller continental normal fault Mmax.Rather, lithosphere yield stress (strength) appears to be the main factor controlling Mmax. In extension, lithosphere is weaker, failing at lower yield stresses than in compression. Although this yield stress difference is consistent with smaller continental normal fault earthquakes, it appears inconsistent with the occurrence of large oceanic normal fault earthquakes. However, the largest oceanic normal fault earthquakes occur near subduction zones where the lithosphere is bending. Laboratory studies indicate that bending lithosphere likely has a higher yield stress than lithosphere in pure extension, which may allow for larger oceanic normal fault earthquakes. Therefore, yield stress—rather than fault geometry alone—appears to be the key factor limiting an earthquake's maximum magnitude.

Bioresorbable stent to manage congenital heart defects in children

Intravascular stents for pediatric patients that degrade without inhibiting vessel growth remain a clinical challenge. Here, poly(L-lactide) fibers (DH-BDS) at two thicknesses, 250 µm and 300 µm, were assembled into large, pediatric-sized stents (Ø10 - Ø20 mm). Fibers were characterized mechanically and thermally, then stent mechanical properties were compared to metal controls, while mass loss and degradation kinetics modeling estimated total stent degradation time. Thicker fibers displayed lower stiffness (1969 ± 44 vs 2126 ± 37 MPa) and yield stress (117 ± 12 vs 137 ± 5 MPa) than thinner counterparts, but exhibited similar fail strength (478 ± 28 vs 476 ± 16 MPa) at higher strains (47 ± 2 vs 44 ± 2%). Stents all exhibited crystallinity between 51.3 – 54.4% and fiber glass transition temperatures of 88.6 ± 0.5°C and 84.6 ± 0.5°C were well above physiological ranges. Radial strength (0.31 ± 0.01 - 0.34 ± 0.02 N/mm) in thinner stents was similar to metal stents (0.24 – 0.41 N/mm) up to Ø14 mm with no foreshortening and thicker coils granted comparable radial strength (0.32 ± 0.02 - 0.34 ± 0.02 N/mm) in stents larger than Ø14 mm. Both 10 mm (1.17 ± 0.02 % and 0.86 ± 0.1 %) and 12 mm (1.1 ± 0.03% and 0.89 ± 0.1%) stents exhibited minimal weight loss over one year. Degradation kinetics models predicted full stent degradation within 2.8 - 4.5 years depending on thickness. DH-BDS exhibiting hoop strength similar to metal stents and demonstrating minimal degradation and strength loss over the first year before completely disappearing within 3 to 4.5 years show promise as a pediatric interventional alternative to current strategies.

Rheology and application of buoyant foam concrete for digital fabrication

In the fresh state, conventional lightweight foam concrete (LWFC) has low yield stress which challenges shape retention and buildability in digital construction. Several literatures attempt to address the rheological performance of 3D printable lightweight foam concrete (3DP-LWFC) in essence. This research presents a comprehensive rheological characterisation with controlled shear rate tests and flow curve tests over different foam volume fractions and densities of 700, 1000 and 1400 kg/m3. LWFC is appropriately adapted for extrusion-based 3D printing in the experimental program by incorporating a small amount of nanopowder (replacing 2% of cement mass) for increased yield shear stress, and calcium sulfoaluminate cement replacing 10% of cement mass for improved thixotropy in the fresh state. Accordingly, this raises the yield stress to 347–812 Pa for 700–1400 kg/m3 LWFC compared to static yield stress below 100 Pa of conventional LWFC, improves thixotropic performance in terms of the rate of reflocculation (Rthix 0.21–3.15 Pa/s) and rate of structuration (Athix 0.06–1.02 Pa/s), viscosity (2.5–3.4 Pa⋅s), and elastic shear modulus evolution. Foam volume is found to significantly influence the rheological properties. To analyse the constructability, shape retention and buildability are investigated, resulting in up to 15 deposited filament layers to be reached in a buildability test. Lastly, a practical example is presented whereby a façade element is printed with 3DP-LWFC at a wet density less than 1000 kg/m3, yielding a lightweight element with buoyant characteristics that further expands the application potential of 3D concrete printing.

Insights on tube rotary draw bending with superimposed localized thermal field

The manufacturing of hollow section profiles using high strength metallic alloys may suffer of relevant drawbacks such as springback, reduced formability as well as wrinkling, which often limit the process capabilities. Localized heating of cross section sectors may allow a significant reduction of these issues thanks to the neutral layer shift and lowered yield stress. The paper describes an analytical approach to provide a fast prediction of the stress and strain distributions in the cross-section and their effects on the springback as consequence of the process thermal and mechanical parameters. Experimental and numerical validations confirm the analytical model reliability.

Influence of temperature on the rheological behaviour of eco-mortar with binary and ternary cementitious blends of natural pozzolana and marble powder

With the advent of new concrete such as low-impact environmental concrete, and the new implementation techniques of cementitious materials such as 3D printing and pumping, it becomes crucial to control the rheological behaviour of these materials taking into account the different climatic conditions. The main objective of this study is to investigate the influence of mineral additions and temperature on the rheological parameters (yield stress, plastic viscosity) and the fresh properties (slump, flow time) of low-impact environmental concrete using concrete-equivalent mortar (CEM) concept. For this purpose, fifteen mixtures of CEM were prepared by substituting the cement with natural pozzolana (PZ) and marble powder (MP) in binary and ternary blend systems. The rheological and fresh properties of CEM mixtures were investigated at different temperatures ranging from 10 °C to 50 °C. The results obtained revealed that, the use of binary and ternary blended cements based on PZ and MP increased the fresh properties and decreased the rheological parameters of CEM tested in a standard environment of temperature 20 °C. In addition, the increase in temperature affected negatively the fresh properties and rheological parameters of all binary mixtures. However, at low temperature (10 °C), the viscosity and yield stress of ternary mixtures have been enhanced.

Hydraulic expansion of lined pipe for offshore pipeline applications

Carbon steel pipe lined with a thin layer of a corrosion resistant alloy is an economical product used in offshore pipelines that carry corrosive hydrocarbons. The liner and carrier pipe are mechanically expanded together so that on unloading they end up in interference contact. The contact pressure that develops is essential for keeping the composite pipeline intact under bending and axial loads experienced during offshore installation and operation. The manufacture of lined pipe by hydraulic expansion is analyzed with a custom model, which is used to establish the effect of various geometric, material, and manufacturing parameters on the contact pressure. The analysis incorporates incremental plasticity that accounts for material hardening and the biaxial states of stress that develop. It is demonstrated that plastification of the carrier pipe is beneficial, and that a relatively low yield stress liner with low hardening, coupled with a high yield stress high hardening carrier pipe increases the contact pressure. The analysis presented and the results should prove to be useful in the design of the manufacturing process of lined pipe aimed for offshore applications.

Effect of PCEs with different structures on hydration and properties of cementitious materials with low water-to-binder ratio

Polycarboxylate ethers (PCEs) with different structures and densities of anchor groups in the backbone were synthesized and characterized. The surface tension of their solutions, their adsorption on cementitious particles and zeta potential of cement-silica fume pastes with PCEs were measured. Their effects on hydration and properties of cement-silica fume paste with low water-to-binder ratio were examined. Results indicated that the adsorption kinetics of theses PCEs on cementitious particles are fitted the pseudo-second-order model. The introduction of long silane chain on PCE decreased its electrostatic adsorption, while PCE was adsorbed onto the surface of particles via both chemical and electrostatic adsorption, when silicon hydroxyl is directly connected to its backbone. In the presence of PCE with higher adsorbed amount, pastes exhibited lower yield stress and higher flowability, and higher strength at 7 d and 28 d. The low plastic viscosity, autogenous and drying shrinkage were related to the low surface tension of PCE solution.

Functional Method of Designing Self-Compacting Concrete.

The article presents a new functional method of designing self-compacting concrete (SCC). The assumptions of the functional method of designing self-compacting concrete were based on the double coating assumption (i.e., it was assumed that the grains of coarse aggregate were coated with a layer of cement mortar, whereas the grains of sand with cement paste). The proposed method is composed of four stages, each of which is responsible for the selection of a different component of the concrete mix. The proposed designing procedure takes into consideration such a selection of the mineral skeleton in terms of the volumetric saturation of the mineral skeleton, which prevents the blocking of aggregate grains, and the designed liquid phase demonstrated high structural viscosity and low yield stress. The performed experimental studies, the simulation of the elaborated mathematical model fully allowed for the verification of the theoretical assumptions that are the basis for the development of the method of designing self-compacting concrete.

Improvement of Strength and Ductility by Combining Static Recrystallization and Unique Heat Treatment in Co-20Cr-15W-10Ni Alloy for Stent Application

The Co-20Cr-15W-10Ni (CCWN, mass%) alloy has excellent corrosion resistance and strength-ductility balance and is applied in almost all balloon-expandable stent platforms. To further reduce the invasiveness of stent placement, it is necessary to reduce the diameter of the stent. That is, both high strength and high ductility should be achieved while maintaining a low yield stress. In our previous studies, it was discovered that low-temperature heat-treatment (LTHT) at 873 K improves the elongation of the CCWN alloy. In this study, we focused on the grain refinement by swaging and static recrystallization to improve the strength of the alloy. The as-swaged alloy was recrystallized at 1373–1473 K for 100–300 s, followed by LTHT. A fine grain structure with an average grain size of 3–17 μm was obtained by static recrystallization. The η-phase (M12X-M6X type precipitates, M: metallic elements, X: C and/or N) formed during the recrystallization at 1373–1448 K. The alloys recrystallized at 1448 and 1473 K had a homogeneous structure with a small variation in the grain size. On the other hand, the alloys recrystallized at 1373 and 1423 K had an inhomogeneous structure in which fine and coarse grains were mixed. Both the strength and ductility of the CCWN alloy were improved by combining high-temperature short-time recrystallization and LTHT.

Study on the seismic behaviour of steel shear plates

To design a steel shear wall, dynamics of stress concentration on the columns and beam under lateral loads is essential. Therefore, it has been suggested that the thickness of plates should be reduced as much as possible. In cases where a plate with low thickness is not available, this is compensated by using either low-yield-stress plate or by preparing some holes in the structure. Two objectives are pursued in this study, namely, the formulation of a new time integration method for evaluating structural seismic behaviour, and to discover the influences of the yield strength of the steel plate and openings on the wall. The results obtained indicate that the proposed scheme can accurately assess the seismic performance of structures. In addition, in the shear wall with low yield stress, where the steel plate has 5% and 10% openings, there are no significant differences between the outputs of widespread and concentrated openings. The behaviours of these two kinds of shear walls are approximately the same.

Lightweight and low thermal conducted face-centered-cubic cementitious lattice materials (FCLMs)

Lightweight and thermal insulative cementitious materials with large porous structures for improving energy efficiency have rapid development currently. However, the design of cementitious materials for energy-efficient building system in terms of low thermal conductivity, excellent mechanical properties and lightweight remains a crucial challenge in construction & building fields. Recently, the polymer-based lattice-inspired structures fabricated by 3D printing technology (3DPT) show a rapid development that achieves a balance of thermal and mechanical properties due to their ordered and large-scale cellular architecture. In this work, a novel category of lattice-inspired cementitious lattice materials was first proposed for applying in the energy-efficient building systems by integrating the 3DPT and traditional casting technology. Taking face-centered cubic (FCC) lattice as an example, the advantages of the proposed fabrication technology and FCLMs are follows: (i) ultralight weight; (ii) enhanced ductility of brittle cementitious materials; (iii) low thermal conductivity. Through the structural and material design, the proposed fabrication technology could effectively overcome the current issues of 3DPT, such as the weakness of interlayer performance and low accuracy (Extrusion-based 3DPT) as well as limited feasible materials (Powder-bed-based 3DPT), in the civil engineering. Statement of SignificanceHow to design cementitious materials for energy-efficient building system in terms of thermal conductivity, mechanical properties and lightweight requirement remains a crucial challenge in construction & building fields. Inspired by the low thermal conductivity and lightweight structure of metamaterials in the previous researches (Song et al., Materials & Design, 2019. 173: 107773-86; Nicholas et al. Nano letter, 2018. 18: 4755-61), here a novel category of lattice-inspired cementitious materials with ordered porous structures has been proposed for energy-efficient building materials with lightweight, low thermal conductivity and good mechanical properties characteristics.Additionally, recently there is increased interest to use 3D concrete printing technology (3DCPT) to automatically manufacture complicated and customized structure. However, currently, 3DCPT encounters many sticky issues, involving that (i) weak interlayer performance induced by cold joints between layers; (ii) deformation under self-weight due to the low yield stress of fresh mix; (iii) probable shrinkage under the low water/cement ratios typically used in printed mortars; (iv) geometrical instability owing to creating suspended structures. It is not a trivial to directly print cementitious porous materials, and therefore this work also achieved a breakthrough in developing cementitious porous materials combining advanced SLA 3D printing and traditional casting technology for the first time. It is worth mention that compared to Extrusion-based 3DCPT and Powder-bed-based 3DCPT, the advantages of the manufacture technology include that (i) automatically printing 3D complex structure; (ii) Optional cementitious materials; (iii) Good interlayer performances of prepared materials.We expect that the proposed design idea and novel manufacture strategy could serve as the guideline to develop material-structural-functional integrated energy-efficient building materials combining 3D printing technology, advanced structure design and high-performance cementitious materials.

Ab Initio Calculations and CALPHAD Assisted Design of L1 <sub>2</sub>-Hardened CoNi-Based Superalloys Exhibiting Low Mass Density, Large Misfit and High Yield Stress

Frequently, CoNi-based superalloys contain a high fraction of W and/or Mo, which stabilize the precipitate phase cause a high density. In this work, new L12-hardened, low-density CoNi-based superalloys were designed combining ab initio and CALPHAD calculations. The alloys exhibit a very high misfit, good phase stability and excellent mechanical strength. From the ab initio calculations it was possible to draw conclusions how different Ni contents and Ti/Al ratios could stabilize the L12 structure of the γ′ phase. Both, Ni and Ti additions lead to alloys that exhibit a higher formation energy of the new type of (Co,Ni)3(Al,Ti) L12 phase compared with the Co3(Al,W) phase. By CALPHAD calculations screening for promising alloy compositions, it was also found that Ni and Cr can increase the solvus temperature and volume fraction of the γ′ phase. Several alloys were studied experimentally and their microstructures, elemental distributions, lattice parameters and the lattice misfit between the γ and γ′ phases at room temperature were evaluated using scanning electron microscopy, transmission electron microscopy, atom probe tomography and high energy X-ray diffraction. It was found that a two-step heat treatment can improve the strength of the new alloys as reflected by hardness test. The new alloys have low mass density and high yield stress compared with conventional Co-based superalloys, Co-Al-W based superalloys and Co-Ti based superalloys, as well as Ni-based superalloys, i.e. Udimet 720Li. The new alloy compositions also overcome the problem of a low lattice misfit associated with high Ni and Cr contents in L1 2 -phase hardened Co-based superalloys and show cuboidal shaped precipitates similar as Co-Al-W and Co-Al-Mo based superalloys.

Bio-inspired surface modification of iron oxide nanoparticles for active stabilization in hydrogels.

Biological materials employ a variety of dynamic interactions in sophisticated composite structures to function adaptively on different time and length scales. Inspired by such designs we develop a novel surface modification approach to promote dynamic interactions between nanoparticles and polymer chains in physical and double network hydrogels. Physical hydrogels are formed via reversible complexation of borate ions with poly(vinyl alcohol) (PVA) and chemical crosslinks are introduced by electron beam irradiation. Dopamine is used for surface modification of magnetic iron oxide nanoparticles (MNPs) in two different ways: the direct treatment results in anchoring via catechol groups, whereas the indirect method leaves the catechol group on the free surface of MNPs. Although the former particles show very good colloidal stability, they lower the network connectivity, which results in lower plateau modulus, faster terminal relaxation, and lower yield stress, presumably due to imposing an extra distance between PVA chains. In contrast to this passive design, the latter particles actively reinforce the network by forming clusters of physical bonds between catechol groups of the individual particles and the monodiol complexes of the borate ions and PVA chains. Moreover, the additional complexes formed upon the introduction of nanoparticles with active surfaces provide further energy dissipation potential and therefore enhance the toughness. This approach can help develop novel hydrogels with superior toughness and multiple stimuli-responsiveness.

Study on material structure evolution of steam turbine rotor under thermal cycling fatigue load

In order to improve the structural strength of the turbine rotor, the dynamic circuit and driving mechanical model of the turbine rotor are established under the thermal cycle fatigue load. The numerical simulation principle of the stress yield evolution process of the rotor structure is analysed. The closed vector method and Lagrange equation are used to establish the mechanical analysis and yield stress model, and the mechanical principle of the thermal cycle fatigue load of the rotor is analysed. On this basis, the yield stress evaluation model is established to realise the material structure evolution analysis. The results show that the method can provide higher accuracy and lower yield stress estimation results, with an average error of 15.74% lower than that of the traditional method, which shows that the method can improve the anti-interference ability of turbine rotor drive and the stress intensity of rotor material structure, with good convergence.

Correlation between shear punch and tensile measurements for an AZ31 Mg alloy processed by equal-channel angular pressing

An AZ31 magnesium alloy was extruded and then processed by equal-channel angular pressing (ECAP) at 200 °C for 1, 2 and 4 passes. The grain structure was refined from 20.2 to 1.6 ?m after 4 passes. The shear punch testing (SPT) technique and uniaxial tensile tests were employed to evaluate the mechanical properties of the extruded and ECAP samples. The 4 pass ECAP alloy showed lower yield stress and higher ductility compared to the as-extruded condition, indicating that texture softening overcame the strengthening effects of grain refinement. The same trends in strength and ductility were also observed in shear punch testing. Three different linear correlations between the shear data and tensile data were established for ductility, yield stress, and ultimate strength. It is shown that SPT is a useful method for evaluating the mechanical properties of small quantities of fine-grained materials processed by ECAP