High-pressure Sliding Research Articles

In Situ Electrical Resistance Measurement of Pure Titanium During Severe Plastic Deformation by High‐Pressure Sliding

In this study, in situ measurements of electrical resistance in pure Ti during severe plastic deformation (SPD) under high pressures are presented. The process of high‐pressure sliding (HPS) is adopted for the SPD so that straining is feasible under various pressures covering α to ω allotropic phase transformation in pure Ti. Anvil surfaces are coated by a plasma‐sprayed alumina layer to maintain electrical insulation between the sample and the anvils during HPS operation. The electrical resistance increases continuously with straining by the HPS processing but the increase in the electrical resistance is more pronounced as the applied pressure increases, particularly when the ω phase formation occurs. The phase transformation is evidenced by X‐Ray diffraction analysis as well as in situ static heating experiment. The continuous increase in the electrical resistance suggests that there is neither critical strain nor avalanche for the phase transformation to the ω phase.

Comparison of Mechanical Properties in Ultrafine Grained Commercial-Purity Aluminum (A1050) Processed by Accumulative Roll Bonding (ARB) and High-Pressure Sliding (HPS)

Comparison of Mechanical Properties in Ultrafine Grained Commercial-Purity Aluminum (A1050) Processed by Accumulative Roll Bonding (ARB) and High-Pressure Sliding (HPS)

Incremental Feeding High-Pressure Sliding (IF-HPS) Process for Upscaling Highly Strained Areas in Metallic Materials with Enhanced Mechanical Properties

Incremental Feeding High-Pressure Sliding (IF-HPS) Process for Upscaling Highly Strained Areas in Metallic Materials with Enhanced Mechanical Properties

Comparison of Mechanical Properties in Ultrafine Grained Commercial-Purity Aluminum (A1050) Processed by Accumulative Roll Bonding (ARB) and High-Pressure Sliding (HPS)

This study presents that A1050 commercial-purity aluminum increases the tensile strength and ductility using the processes of accumulative roll bonding (ARB) and high-pressure sliding (HPS). Both processes yield a similar tensile strength exceeding 240 MPa after processing by ARB for 10 cycles and by HPS for the sliding distance of 15 mm, respectively. The stress-strain behavior is evaluated through microstructure observations and measurements of strain hardening rates. Significant grain refinement with well-defined grain boundaries is responsible for the strength increase. The grain refinement also leads to an increase in strain hardening rate and thus an increase in the ductility.

Enhancement of Activation and Hydrogen Storage Kinetics of TiFe(Mn) Using High-Pressure Sliding (HPS) Process

A titanium-iron intermetallic with minor addition of manganese (TiFe0.7Mn0.3) was processed by severe plastic deformation through high-pressure sliding (HPS). A rectangular strip sample was embedded in stainless steel and strained under a pressure of 4 GPa at room temperature. The hydrogen storage kinetics and activation of the HPS-processed sample were significantly enhanced in comparison with the as-received ingot without the HPS processing.

Incremental Feeding High-Pressure Sliding (IF-HPS) Process for Upscaling Highly Strained Areas in Metallic Materials with Enhanced Mechanical Properties

This paper presents an overview of the recent development of incremental feeding high-pressure sliding (IF-HPS) process for grain refinement of metallic sheets with enlarged areas. The IF-HPS process is a method of severe plastic deformation (SPD) under high pressure without increasing the machine capacity. The IF-HPS process combines an incremental feeding technique with the high-pressure sliding (HPS) process so that a severely deformed area can be extended. Development of the IF-HPS process includes the use of flat-type anvils instead of groove-type anvils, which makes it easier to enlarge the SPD-processed areas. The development is also described in terms of the sliding mode and the feeding pattern, where the former is determined by the sliding distance and the numbers of the reciprocation of the sliding and the latter by the feeding distance and the feeding direction. The application of the IF-HPS process is made to metallic materials such as a Ni-based superalloy (Inconel 718), a Ti-6Al-7Nb alloy (F1295) and commercially available Al alloys (A1050, A3105, A5052 and A5182). It is shown that the grain refinement is successfully achieved so that superplastic elongation more than 400% is attained in the Ni- and Ti-based alloys, and the room-temperature tensile strength is well enhanced in the Al alloys. It is then demonstrated that the IF-HPS process is promising to extend the SPD-processed area without increasing the machine capacity. Furthermore, a new approach is suggested for material design, such as the hybrid materials composed of conventional and fine-grained materials and functionally graded materials.

高圧スライド法を用いたTi同素変態のその場放射光X線解析

In this study, severe plastic deformation through high-pressure sliding (HPS) was applied for in situ high-energy X-ray diffraction analysis at SPring-8 in JASRI (Japan Synchrotron Radiation Research Institute). Allotropic transformation of pure Ti was examined in terms of temperatures, pressures and imposed strain using a miniaturized HPS facility. The true pressure applied on the sample was estimated from the peak shift. Peak broadening due to local variation of pressure was reduced using white X-ray. The phase transformation from α phase to ω phase occurred at a pressure of ∼4.5 GPa. Straining by the HPS processing was effective to promote the transformation to the ω phase and to maintain the ω phase even at ambient pressure. The reverse transformation from ω phase to α phase occurred at a temperature of ∼110℃ under ambient pressure, while under higher pressure as ∼4 GPa, the ω phase remained stable even at ∼170℃ covered in this study. It was suggested that the reverse transformation from the ω phase to the α phase is controlled by thermal energy.

Mechanical Properties and Microstructures of Highly Fe-Containing Al–Mg–Si Alloys Processed by Severe Plastic Deformation under High Pressure

In this study, A6022-based Al–Mg–Si alloys with three additional Fe contents are processed by high-pressure torsion (HPT) and high-pressure sliding (HPS). Both processes yield a similar tensile strength exceeding 400 MPa. Fe intermetallics were finely and homogeneously fragmented to an average size of ∼2 µm by the HPT process. The high tensile strength is attributed to such a fine and homogeneous fragmentation of Fe intermetallics. It is also demonstrated that the finely fragmented Fe intermetallics play an important role to maintain finer grain size even after solution treatment.

Compared microstructure and properties of an AlZnMgCu alloy processed by high pressure sliding and high-pressure torsion

Achieving high yield strength via submicrometer grain size and nanoscaled precipitation has been reached in 7### aluminum alloys thanks to severe plastic deformation (SPD) by High Pressure Torsion (HPT) process. Unfortunately, this technique has inherently strong limitations since only small parts can be processed and the plastic strain is not homogeneous. These limitations prevent large scale production of Ultra Fine Grain (UFG) materials for potential applications. A recent severe plastic deformation process, High Pressure Sliding (HPS) developed by Fujioka and Horita, allows to homogeneously deform large scale sheets by shear at higher speed. In this work, the competition between precipitation, grain growth and recrystallization during heat treatments after SPD was studied in depth for an AlZnMgCu alloys deformed by HPS with two deformation levels (γ ≈ 15 and γ ≈ 20) in order to investigate if the high mechanical properties obtained by HPT can be reached by HPS. Microstructures analyses after deformation and ageing were carried out by transmission electron microscopy and in situ small angle X ray scattering and then related to the mechanical behavior evaluated by tensile tests. Experimental data show very similar microstructures after HPS and HPT, with a good thermal stability thanks to the competition between precipitation, recrystallization and recovery. The obtained microstructural features lead to exceptional yield strength (>800 MPa) as compared to the classical aluminum alloys. This study is therefore very promising towards the aim of obtaining very high yield strength aluminum alloys suitable for applications.

Creep Resistance of S304H Austenitic Steel Processed by High-Pressure Sliding.

Sheets of coarse-grained S304H austenitic steel were processed by high-pressure sliding (HPS) at room temperature and a ultrafine-grained microstructure with a mean grain size of about 0.14 µm was prepared. The microstructure changes and creep behavior of coarse-grained and HPS-processed steel were investigated at 500–700 °C under the application of different loads. It was found that the processing of S304H steel led to a significant improvement in creep strength at 500 °C. However, a further increase in creep temperature to 600 °C and 700 °C led to the deterioration of creep behavior of HPS-processed steel. The microstructure results suggest that the creep behavior of HPS-processed steel is associated with the thermal stability of the SPD-processed microstructure. The recrystallization, grain growth, the coarsening of precipitates led to a reduction in creep strength of the HPS-processed state. It was also observed that in the HPS-processed microstructure the fast formation of σ-phase occurs. The σ-phase was already formed during slight grain coarsening at 600 °C and its formation was enhanced after recrystallization at 700 °C.

Compared Microstructure and Properties of an Alznmgcu Alloy Processed by High Pressure Sliding and High-Pressure Torsion

Compared Microstructure and Properties of an Alznmgcu Alloy Processed by High Pressure Sliding and High-Pressure Torsion

Influence of High Pressure Sliding and Rotary Swaging on Creep Behavior of P92 Steel at 500 °C

High-pressure sliding (HPS) and rotary swaging (RS) at room temperature were used to form severely deformed microstructures in martensitic creep-resistant P92 steel. The deformed microstructures contained markedly different ratios of low- and high-angle grain boundaries (LAGBs/HAGBs). The application of the RS method, with an imposed equivalent strain of 1.4, led to the formation of a heterogeneous microstructure with a high number of LAGBs, while the HPS method, with an imposed equivalent strain of 7.8, led to the formation of a relatively homogeneous ultrafine-grained microstructure with a significant predominance of HAGBs. Microstructure analyses after creep testing showed that the microstructure of RS- and HPS-processed P92 steel is quite stable, but a slight coarsening of subgrains and grains during creep testing can be observed. Constant load tensile creep tests at 500 °C and initial stresses ranging from 300 to 900 MPa revealed that the specimens processed by HPS exhibited higher creep strength (slower minimum creep rate) and ductility compared to the coarse-grained and RS-processed P92 steel. However, the HPS-processed P92 steel also exhibited lower values of stress exponent n than the other investigated states of P92 steel. For this reason, the differences in minimum creep rates determined for different states decrease with decreasing values of applied stress, and at applied stresses lower than 500 MPa, the creep resistance of the RS-processed state is higher than the creep resistance of the HPS-processed state.

Homogeneous Strain Introduction Using Reciprocation Technique in High-Pressure Sliding

Homogeneous Strain Introduction Using Reciprocation Technique in High-Pressure Sliding

Mechanical properties and electrical conductivity of ultrafine-grained aluminum consolidated by high-pressure sliding

High-pressure sliding (HPS) was successfully applied for consolidation of aluminum powders at room temperature. A full densification was attained by the HPS processing under 2 GPa through 3 mm sliding (equivalent strain of 2.3). The consolidated samples showed ultrafine-grained structures with average grain sizes of ~0.85 μm and ~1.0 μm for the powder sizes of 45 μm and 75 μm, respectively. When the consolidated samples were annealed at a temperature in the range of 473–673 K, grain growth was significantly reduced by the presence of oxide particles originated from the surface layers on the powders. The hardness and tensile strength increased with increasing imposed strain and decreased with annealing but they remained higher in the consolidated samples than that in the bulk sample. The electrical conductivity increased with straining and saturated to a value of 50%IACS in a manner similar to the density. The strengthening mechanisms were evaluated in terms of particles dispersions as well as grain refinement. This study demonstrates that the HPS processing provides a useful approach to consolidate metallic powders into bulk form for application of electrical wires with higher tensile strength and enhanced thermal stability.

Severe Plastic Deformation under High Pressure: Upsizing Sample Dimensions

It is well known that severe plastic deformation (SPD) produces ultrafine-grained structures in bulk metallic materials. The SPD process becomes more versatile when it is performed under high pressure as high-pressure torsion (HPT) and high-pressure sliding (HPS). Not only the grain size is more refined but also the process is applicable to hard-to-deform materials such as intermetallics, semiconductors and ceramics, leading to enhancement of functional properties as well as structural properties. The major drawback is that the sample size is small so that the applicability is limited to a laboratory scale and it is an important subject to increase the sample dimensions. This paper presents an overview describing efforts devoted thus far to deal with this upscaling issue.

Achieving Grain Refinement of Upsized Al–3Mg–0.2Sc (mass%) Round Rods Using Multi-Pass High-Pressure Sliding (MP-HPS)

Achieving Grain Refinement of Upsized Al–3Mg–0.2Sc (mass%) Round Rods Using Multi-Pass High-Pressure Sliding (MP-HPS)

Mechanical Properties and Electrical Conductivity of Ultrafine-Grained Aluminum Consolidated by High-Pressure Sliding

Mechanical Properties and Electrical Conductivity of Ultrafine-Grained Aluminum Consolidated by High-Pressure Sliding

Incremental Feeding High-Pressure Sliding for Grain Refinement of Large-Scale Sheets: Application to Inconel 718

This study updates a process of high-pressure sliding (HPS) recently developed as a severe plastic deformation process under high pressure for grain refinement of sheet samples. The updated version, which we call the incremental feeding HPS (IF-HPS), consists of sliding for SPD and feeding for upsizing the SPD-processed area so that, without increasing the capacity of processing facility, it is possible to cover a much larger area with an SPD-processed ultrafine-grained structure with a grain size of ~ 120 nm. For the IF-HPS processing, anvils with flat surfaces but without grooves are used in an unconstrained condition, and the feeding distance is set equal to the deformed width. A Ni-based superalloy (Inconel 718) is processed by the IF-HPS under 4 GPa at room temperature, and it is possible to obtain an SPD-processed sheet with dimensions of approximately 100 × 100 × 1 mm3. Strain distribution and evolution were examined by hardness measurement and simulation using a finite element method. Tensile tests were conducted using tensile specimens extracted from the IF-HPS-processed sheet. Advent of high strain rate superplasticity with the total elongation of more than 400 pct was confirmed by pulling the tensile specimens with an initial strain rate of 2.0 × 10−2 s−1 at a temperature as low as 1073 K. The formability of the IF-HPS-processed sheet was confirmed by successful cup forming. It was also confirmed that the restoration after the superplastic deformation was feasible by subjecting to conventional heat treatment used for Inconel 718.

巨大ひずみ領域の大面積化を目指した逐送高圧スライド加工法の開発

巨大ひずみ領域の大面積化を目指した逐送高圧スライド加工法の開発

Extra Strengthening and Superplasticity of Ultrafine-Grained A2024 Alloy Produced by High-Pressure Sliding

Extra Strengthening and Superplasticity of Ultrafine-Grained A2024 Alloy Produced by High-Pressure Sliding