Technical parameters affecting grain refinement by high pressure torsion

Hohenwarter, Anton; Bachmaier, Andrea; Gludovatz, Bernd; Scheriau, Stephan; Pippan, Reinhard

doi:10.3139/146.110224

Cited by 173 publications

(125 citation statements)

References 23 publications

Supporting

Mentioning

109

Contrasting

Order By: Relevance

“…This is supported by the differences in microstructural observations along this direction. A sufficient high number of turns may reduce heterogeneity, by filling the alloy in-between the anvils and achieving a significant sticking condition which then increases the deformation and microstructural homogeneity [5,12,15,40,41]. The distribution of microhardness along the vertical and horizontal cross-sections showed considerable consistency for the current alloy processed at each specific processing temperature.…”

Section: Development Of Microhardnessmentioning

confidence: 94%

“…The feasibility of HPT processing at 296 K for the AZ91 magnesium alloy can be attributed to the presence of hydrostatic pressure, which prevents propagation of fracture during processing [6][7][8]. Furthermore, the geometry of the processing zone constrains the alloy within a specific volume as illustrated earlier and thus activation of twinning [8,15,16]. The XRD observations indicate the orientation of the processed microstructure towards twinning and basal deformation modes under HPT conditions that facilitate processing at room temperature [16].…”

Section: Discussionmentioning

confidence: 99%

“…The low value of temperature rise can be attributed to (1) the heat loss from relatively small samples in contact with the much larger HPT anvils and (2) due to the low strain rates of deformation in HPT processing [31]. A further factor, making the heat generated low, is the lower friction expected between the relatively lower strength magnesium alloy and the high strength (high speed tool steel) anvils [15,31]. As a result, any temperature rise due to processing is considered negligible and unlikely to produce any occurrence of recrystallization or grain growth during processing at room temperature [32].…”

Section: Grain Refinement In Az91 Alloymentioning

confidence: 99%

See 2 more Smart Citations

Evolution of microstructure in AZ91 alloy processed by high-pressure torsion

et al. 2015

View full text Add to dashboard Cite

An investigation has been conducted on AZ91 magnesium alloy processed in high-pressure torsion (HPT) at 296, 423 and 473 K for different numbers of turns. The microstructure has altered significantly after processing at all processing temperatures. Extensive grain refinement has been observed in the alloy processed at 296 K with apparent grain sizes reduced down to 35 nm. Segmentation of coarse grains by twinning has been observed in the alloy processed at 423 K and 473 K with average apparent grain sizes of 180 nm and 250 nm. Substantial homogeneity in microhardness has been observed in the alloy processed at 296 K compared to that found at 423 K and 473 K. The ultrafine-grained AZ91 alloy exhibited a significant dependence of the yield strength on grain size as shown by the microhardness measurements, and it obeys the expected Hall-Petch relationship. The alloying elements, fraction of nano-sized particles of b-phase, and the dominance of basal slip and pyramidal modes have additional effects on the strengthening of the alloy processed at 296 K.

show abstract

Section: Development Of Microhardnessmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Grain Refinement In Az91 Alloymentioning

confidence: 99%

See 1 more Smart Citation

Evolution of microstructure in AZ91 alloy processed by high-pressure torsion

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Processing by HPT is usually undertaken on disk-shaped specimens, 31 although the processing has been extended also to cylindrical [32][33][34] and sheet 35 samples. The conventional HPT disks are generally cut from a single metal or alloy, but recently it was shown that semicircular disks of Al and Cu may be successfully bonded through a solid-state reaction at ambient temperature by using HPT processing through up to 100 turns.…”

Section: Fabricating High-strength Metal-matrix Nanocomposites By Higmentioning

confidence: 99%

Producing Bulk Ultrafine-Grained Materials by Severe Plastic Deformation: Ten Years Later

Valiev

Estrin

Horita

et al. 2016

JOM

404

186

View full text Add to dashboard Cite

It is now well established that the processing of bulk solids through the application of severe plastic deformation (SPD) leads to exceptional grain refinement to the submicrometer or nanometer level. Extensive research over the last decade has demonstrated that SPD processing also produces unusual phase transformations and leads to the introduction of a range of nanostructural features, including nonequilibrium grain boundaries, deformation twins, dislocation substructures, vacancy agglomerates, and solute segregation and clustering. These many structural changes provide new opportunities for fine tuning the characteristics of SPD metals to attain major improvements in their physical, mechanical, chemical, and functional properties. This review provides a summary of some of these recent developments. Special emphasis is placed on the use of SPD processing in achieving increased electrical conductivity, superconductivity, and thermoelectricity, an improved hydrogen storage capability, materials for use in biomedical applications, and the fabrication of high-strength metal-matrix nanocomposites.

show abstract

“…Two important factors that are essential for the torsional straining of disc samples during HPT processing are hydrostatic pressure and micro-roughness of the anvil cavity surface [8]. For torsional straining a minimum pressure is needed in order to obtain sufficient frictional force so that no relative sliding between the anvil and the specimen surface occurs.…”

Section: Introductionmentioning

confidence: 99%

Investigating Anvil Alignment and Anvil Roughness on Flow Pattern Development in High-Pressure Torsion

2016

View full text Add to dashboard Cite

High-pressure torsion (HPT) is a processing technique in which samples are subjected to a high pressure and torsional straining. Anvil alignment and anvil roughness are two important factors related to the successful application of the HPT processing technique. Using a two-phase duplex stainless steel as a model material, experiments were conducted by placing the anvils in different amounts of initial misalignment. Experiments show that the flow patterns (the development of double-swirl patterns) in HPT are dependent upon the alignment of the anvils within the HPT facility. Through carefully designed experiments, it is shown that the presence of a double-swirl is a feature of HPT processing when the initial positions of the anvils have a small lateral misalignment. The effect of the double-swirl patterns on the hardness evolution was also evaluated quantitatively. By comparing the flow patterns developed on the disc upper surface using both rough and smooth anvils with a fixed anvil misalignment, it was demonstrated that there are some differences in the flow patterns which are dependent upon the anvil surface roughness.

show abstract

Technical parameters affecting grain refinement by high pressure torsion

Cited by 173 publications

References 23 publications

Evolution of microstructure in AZ91 alloy processed by high-pressure torsion

Evolution of microstructure in AZ91 alloy processed by high-pressure torsion

Producing Bulk Ultrafine-Grained Materials by Severe Plastic Deformation: Ten Years Later

Investigating Anvil Alignment and Anvil Roughness on Flow Pattern Development in High-Pressure Torsion

Contact Info

Product

Resources

About