Effect of the heat treatment prior to extrusion on the direct hot-extrusion of aluminium powder compacts

Zubizarreta, C.; Giménez, Sixto; Martín, José Manuel Perlado; Iturriza, I.

doi:10.1016/j.jallcom.2007.12.035

Cited by 13 publications

(16 citation statements)

References 34 publications

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“…In addition, atomised powders of aluminium and its alloys have a fine and homogeneous microstructure, extrusion (PE) and powder forging (PF) are the most promising PM processing methods which have been developed for the production of fully dense, high-performance materials from powders [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…In addition to strain hardening, densification during deformation can enhance the flow stress of the material, which is known as densification hardening [23]. In the case of powderbased porous materials, such as powder compacts, due to friction between particles, redundant work is required to weld powder particles together, break welds between particles, and re-weld them together [10]. Thus, information on the deformation behaviour of bulk aluminium alloys is not usable for the deformation of porous alloys with similar chemical compositions.…”

Section: Introductionmentioning

confidence: 99%

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Hot deformation behaviour and flow stress prediction of 7075 aluminium alloy powder compacts during compression at elevated temperatures

Taleghani

Ruiz-Navas

Salehi

et al. 2012

Materials Science and Engineering: A

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Abstract:In the present study, the hot deformation behaviour of 7075 aluminium alloy powder compacts was studied by performing hot compression tests on a Gleeble 3800 machine. The main objectives were to evaluate the effect of the relative green density on the hot deformation behaviour and to model and predict the hot deformation flow stress of powder compacts using constitutive equations. For this pur-pose, powder compacts with relative green densities ranging from 83 to 95%, which were prepared by uniaxial cold pressing a commercial pre-mixed powder, were hot compressed at temperatures ranging from 350 • Cto450 • C and at true strain rates ranging from 0.01 s −1 to 10 s −1 . The true stress-true strain curves of the powder compacts exhibited a peak stress at a critical strain after which the flow stress remained nearly constant. As the deformation temperature increased or the strain rate and green density decreased, a decrease in the peak stress level was observed. The relationship between deformation tem-perature, strain rate, and the peak flow stress of powder compacts was described by the Zener-Hollomon parameter in an exponential equation containing relative green density compensated material constants and the deformation activation energy. The peak flow stresses calculated from the proposed formula were in good agreement with the experimental results, which confirms the applicability of the employed method for the prediction of the hot deformation flow stress of porous materials with different relative green densities.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hot deformation behaviour and flow stress prediction of 7075 aluminium alloy powder compacts during compression at elevated temperatures

Taleghani

Ruiz-Navas

Salehi

et al. 2012

Materials Science and Engineering: A

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“…In a previous work by Zubizarreta et al [18], Alumix 13 premix which is basically a mixture of elemental Al and Cu powders has been consolidated by hot extrusion. Although different heat treatments prior to extrusion have been performed, all of the bulk alloys processed by these researchers show banded microstructures and contain porosity and pure Cu particles, thus resulting in low hardness values for the extrusion products.…”

Section: Introductionmentioning

confidence: 99%

Microstructural and mechanical characterisation of 7075 aluminium alloy consolidated from a premixed powder by cold compaction and hot extrusion

2014

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Abstract:The present work concerns the processing of 7075 Al alloy by cold compaction and hot extrusion of a pre-mixed powder. To this end, a premixed Al-Zn-Mg-Cu powder, Alumix 431D, was uniaxially cold pressed at 600 MPa into cylindrical compacts 25 mm in diameter and 15 mm thick. Subsequently, selected green compacts were subjected to either a delubrication or presintering heat treatment. Extrusion of the pow-der compacts was performed at 425 °C using an extrusion ratio of 25:1.No porosity was present in the microstructures of the extruded alloys. Heat treatment prior to extrusion had a great effect on the degree of alloy development in powder compacts and, as a direct consequence, remarkably affected the extru-sion process and the as-extruded microstructures and mechanical properties of the processed materials. Hot extrusion caused banded structures for the alloys consolidated from the green and delubricated pow-der compacts. The alloy extruded from the presintered powder compact showed a fine, recrystallized microstructure which resulted in a superior combination of mechanical properties for the consolidated material.

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“…Compared with other PM routes such as sintering and hot pressing (HP), the shear stresses involved in PE and PF make them ideal processes for the production of bulk Mg products from powder mixtures. These shear stresses can break the oxide layer covering the surfaces of Mg-based powder particles, which results in a well-bonded microstructure and superior afterconsolidation mechanical properties [12]. Furthermore, it is a well-known fact that the mechanical properties of Mg alloys can be effectively improved by refining their grain structures through recrystallization, which generally occurs during hot deformation of these materials.…”

Section: Introductionmentioning

confidence: 99%

“…In addition to strain hardening, densification during deformation can enhance the flow stress of the material, which is known as densification hardening [21]. In the case of powder-based porous materials, such as powder compacts, due to friction between particles, redundant work is required to weld powder particles together, break welds between particles, and re-weld them together [12]. Thus, information on the deformation behavior of bulk Mg alloys may not be completely usable for the deformation of porous alloys with similar chemical compositions.…”

Section: Introductionmentioning

confidence: 99%

Hot deformation behavior and workability characteristics of AZ91 magnesium alloy powder compacts—A study using processing map

Taleghani

Torralba

2013

Materials Science and Engineering: A

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This study examined the hot deformation behavior and workability characteristics of AZ91 Mg alloy powder compacts by performing hot compression tests with a Gleeble 3800 machine. To this end, powder compacts with a relative green density of 93% were hot-compressed at temperatures ranging from 150 1Cto5001C and at true strain rates ranging from 0.001 s −1 to 10 s −1 . The true stress-true strain curves peaked at low strains, after which the flow stress increased slightly or remained constant. The work hardening rate decreased with increasing deformation temperature or strain rate. Processing maps were developed for all of the hot compression tests at strains of 0.1, 0.5, and 0.8, which represented a safe deformation domain at deformation temperatures and strain rates in the ranges of 150-300 1C and 0.001-0.01 s −1 . Kinetic analysis of the flow stress data for the safe deformation domain yielded an activation energy of 75 kJ/mol which is lower than those previously reported for the hot compression of bulk AZ91 Mg alloy. According to the developed processing maps and the microstructures of the hot-compressed specimens, the optimum hot working window for AZ91 Mg alloy powder compacts was determined to lie between 275-325 1C and 0.001-0.01 s −1 .

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Effect of the heat treatment prior to extrusion on the direct hot-extrusion of aluminium powder compacts

Cited by 13 publications

References 34 publications

Hot deformation behaviour and flow stress prediction of 7075 aluminium alloy powder compacts during compression at elevated temperatures

Hot deformation behaviour and flow stress prediction of 7075 aluminium alloy powder compacts during compression at elevated temperatures

Microstructural and mechanical characterisation of 7075 aluminium alloy consolidated from a premixed powder by cold compaction and hot extrusion

Hot deformation behavior and workability characteristics of AZ91 magnesium alloy powder compacts—A study using processing map

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