Microstructural evolution and the mechanical properties of an aluminum alloy processed by high-pressure torsion

Sabbaghianrad, Shima; Kawasaki, Megumi; Langdon, Terence G.

doi:10.1007/s10853-012-6524-x

Cited by 81 publications

(60 citation statements)

References 43 publications

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“…Second, with increasing numbers of turns there is a significant increase in hardness in the central region of the disk but at the outer edge the hardness values remain essentially constant thereby confirming the development of a saturation condition. The tendency for lower hardness values to occur initially in the centers of the disks is consistent with earlier reports for several different materials including Al [32] and Cu [33] alloys and the gradual transition to a saturation hardness is also consistent with earlier observations [34,35]. In the present experiments, the data in Fig.…”

Section: Hardness and Microstructural Evolution During Hpt Processingsupporting

confidence: 93%

Using an Al–Cu binary alloy to compare processing by multi-axial compression and high-pressure torsion

Zhang

et al. 2013

Materials Science and Engineering: A

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a b s t r a c tAn Al-4% Cu alloy was selected as a model material in order to compare two different procedures for imposing severe plastic deformation: multi-axial compression (MAC) and high-pressure torsion (HPT). In MAC a compressive strain is applied to prismatic samples in a sequential order along three orthogonal directions and the process is repeated to large numbers of passes in order to attain high strains. In HPT a thin disk is held between anvils and subjected to a high applied pressure and concurrent torsional straining. The results show that HPT is the optimum procedure for producing a homogeneous ultrafinegrained material. Specifically, HPT is preferable because it produces materials having a larger degree of homogeneity and the equilibrium grain sizes are smaller and the Vickers microhardness values are higher than when processing by MAC.

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Section: Hardness and Microstructural Evolution During Hpt Processingsupporting

confidence: 93%

Using an Al–Cu binary alloy to compare processing by multi-axial compression and high-pressure torsion

Zhang

et al. 2013

Materials Science and Engineering: A

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“…1a. Effect of grain size on superplastic strain rate in Al alloys; [7] datum points for ECAP [11][12][13][14][15][16][17][18][19][20] are in black and for HPT [21][22][23][24][25][26][27][28][29] in red; the encircling ovals are in blue for ECAP and pink for HPT and the solid line corresponds to eq. (2) in the text.…”

Section: Figure Captionsmentioning

confidence: 99%

“…[7,10] The experimental results shown in Fig. 1[a] are taken from various reports for Al alloys, [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] and in Fig. 1 [b] there are similar sets of data for a range of Mg alloys [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] where the upper solid lines in Figs 1[a] and [b] show the predicted normalized strain rates derived using eq.…”

Section: Introductionmentioning

confidence: 99%

The Strength–Grain Size Relationship in Ultrafine-Grained Metals

Balasubramanian

Langdon

2016

Metall Mater Trans A

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Metals processed by severe plastic deformation [SPD] techniques, such as equal-channel angular pressing [ECAP] and high-pressure torsion [HPT], generally have submicrometer grain sizes. Consequently, they exhibit high strength as expected on the basis of the HallPetch [H-P] relationship. Examples of this behavior are discussed using data on Ti, Al-Mg 1 and Ni. These materials typically have grain size above ~50 nm where softening is not expected. An increase in strength is usually accompanied by a decrease in ductility. High strength and ductility can be achieved simultaneously by imposing high strains to give both ultrafine grain sizes and a high fraction of high-angle grain boundaries. An example is presented for a cast Al-7% Si alloy processed by HPT. In some cases, SPD may produce a fine grain size but also lead to a weakening due to microstructural changes as in ECAP of an Al-7034 alloy and HPT of Zn-22% Al. In SPD-processed materials, grain boundary segregation and nanostructural features are present which may lead to higher strengths than those predicted by the H-P relationship in some alloys having nano grain sizes.

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“…The development of a high initial hardness at very low strains and the subsequent decrease in hardness to a lower plateau value is designated softening with rapid recovery [17] and later it was fully documented in experiments on high purity Al where the HPT processing was performed through fractional numbers of revolutions between 1/8 and 1 turn [19,20] or hardness values were recorded on different sectional planes throughout the disks [21]. The occurrence of softening with rapid recovery appears to be almost unique to high purity aluminum because aluminum of lower purity (99.7%) [22] and numerous Al-based alloys [23][24][25][26][27][28][29][30][31][32][33] exhibit conventional hardening without recovery. Nevertheless, there are two recent reports of softening with rapid recovery in the h.c.p.…”

Section: Introductionmentioning

confidence: 95%

Microstructure and microhardness of OFHC copper processed by high-pressure torsion

Almazrouee

Al‐Fadhalah

Alhajeri

et al. 2015

Materials Science and Engineering: A

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An ultra-high purity oxygen free high conductivity (OFHC) Cu was investigated to determine the evolution of microstructure and microhardness during processing by highpressure torsion (HPT). Disks were processed at ambient temperature, the microstructures were observed at the center, mid-radius and near-edge positions and the Vickers microhardness was recorded along radial directions. At low strains, Σ3 twin boundaries are formed due to dynamic recrystallization before microstructural refinement and ultimately a stabilized ultrafine grain structure is formed in the near-edge position with an average grain size of ~280 nm after 10 turns. Measurements show the microhardness initially increases to ~150 Hv at an equivalent strain of ~2, then falls to about ~80 Hv during dynamic recrystallization up to a strain of ~8 and thereafter increases again to a saturated value of ~150 Hv at strains above ~22. The delay in microstructure and microhardness homogeneity by dynamic recrystallization is attributed to the high purity of Cu that enhances dislocation mobility and causes dynamic softening during the early stages of straining.

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Microstructural evolution and the mechanical properties of an aluminum alloy processed by high-pressure torsion

Cited by 81 publications

References 43 publications

Using an Al–Cu binary alloy to compare processing by multi-axial compression and high-pressure torsion

Using an Al–Cu binary alloy to compare processing by multi-axial compression and high-pressure torsion

The Strength–Grain Size Relationship in Ultrafine-Grained Metals

Microstructure and microhardness of OFHC copper processed by high-pressure torsion

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