The Experts below are selected from a list of 2946 Experts worldwide ranked by ideXlab platform

Julie M. Schoenung - One of the best experts on this subject based on the ideXlab platform.

  • Atom-Probe Tomographic Study of Precipitation in an Ultrafine-grained Al-Zn-Mg- Cu Alloy (Al 7075)
    2016
    Co-Authors: Julie M. Schoenung, Haiming Wen, Dieter Isheim, David N Seidman, E J Lavernia, David Seidman, Enrique J
    Abstract:

    Precipitation-hardened alloys can be further strengthened by reducing the grain size down to the ultrafine regime (<1 μm) and thereby incorporating significant grain boundary (GB) strengthening [1, 2]. The ultrafine-grained (UFG) structure is expected to induce an influence on the precipitation behavior, because of the significantly reduced length scale. Nevertheless, there have been very limited studies on the effect of length scale on precipitation [3]. The present study was undertaken to obtain quantitative information on the differences in precipitation behavior between UFG structure and the traditional coarse-grained (CG) counterpart, and to provide fundamental insights into the underlying mechanisms. Al 7075 alloy, with major alloying elements of Zn, Mg and Cu, was selected for study because of its technological importance and the existing extensive studies on precipitation phenomena in CG Al 7075. An UFG Al 7075 alloy was fabricated via powder cryomilling, degassing, hot isostatic pressing and extrusion, followed by solution treatment and artificial aging (T6 Temper); a CG counterpart was prepared from unmilled CG powders using the same degassing, consolidation and heat treatment rout

  • Cu Alloy (Al 7075)
    2016
    Co-Authors: David N Seidman, Julie M. Schoenung, Haiming Wen, Dieter Isheim, E J Lavernia, David Seidman, See Profile, Enrique J
    Abstract:

    Precipitation-hardened alloys can be further strengthened by reducing the grain size down to the ultrafine regime (<1 μm) and thereby incorporating significant grain boundary (GB) strengthening [1, 2]. The ultrafine-grained (UFG) structure is expected to induce an influence on the precipitation behavior, because of the significantly reduced length scale. Nevertheless, there have been very limited studies on the effect of length scale on precipitation [3]. The present study was undertaken to obtain quantitative information on the differences in precipitation behavior between UFG structure and the traditional coarse-grained (CG) counterpart, and to provide fundamental insights into the underlying mechanisms. Al 7075 alloy, with major alloying elements of Zn, Mg and Cu, was selected for study because of its technological importance and the existing extensive studies on precipitation phenomena in CG Al 7075. An UFG Al 7075 alloy was fabricated via powder cryomilling, degassing, hot isostatic pressing and extrusion, followed by solution treatment and artificial aging (T6 Temper); a CG counterpart was prepared from unmilled CG powders using the same degassing, consolidation and heat treatment route [3]. The precipitation behavior in the UFG alloy was studied by atom-probe tomography (APT) an

  • coupling of dislocations and precipitates impact on the mechanical behavior of ultrafine grained al zn mg alloys
    Acta Materialia, 2016
    Co-Authors: Hanry Yang, E J Lavernia, Troy D Topping, Ali Yousefiani, Julie M. Schoenung
    Abstract:

    Abstract Intragranular coupling of dislocations and precipitates is accomplished in an ultrafine grained aluminum 7000 series alloy through a unique thermo-mechanical processing route that involves high strain rate extrusion at ambient Temperature as the last step. The as-extruded materials also exhibited a unique bimodal microstructure consisting of: (1) elongated lamellar grains with dimensions of ∼1 μm consisting of sub-grains via low angle grain boundaries, and (2) ultrafine grains approximately ∼100 nm in size with high angle grain boundaries. Our investigation shows that coupling of dislocations and precipitates within the ultrafine grains has a beneficial impact on the mechanical behavior, and results in an extremely high strength, i.e., ultimate tensile strength ∼878 MPa, with uniform elongation of 4.1% strain at fracture. Interestingly, the T6 Temper leads to a decrease in strength for the ultrafine grained material with intragranular dislocations while it enhances ductility, which is opposite the behavior observed in the ultrafine grained material that does not contain a high density of intragranular dislocations. This phenomenon is attributed to the loss in dislocation strengthening and grain boundary strengthening, which could not be compensated for by the strength increase due to precipitation. The underlying mechanisms are discussed on the basis of in-situ heating in a transmission electron microscope, theoretical analysis of diffusion controlled precipitation and microstructure characterization, including transmission Kikuchi diffraction.

  • mechanical behavior and strengthening mechanisms in ultrafine grain precipitation strengthened aluminum alloy
    Acta Materialia, 2014
    Co-Authors: Haiming Wen, Troy D Topping, Dieter Isheim, David N Seidman, E J Lavernia, Julie M. Schoenung
    Abstract:

    To provide insight into the relationships between precipitation phenomena, grain size and mechanical behavior in a complex precipitation-strengthened alloy system, Al 7075 alloy, a commonly used aluminum alloy, was selected as a model system in the present study. Ultrafine-grained (UFG) bulk materials were fabricated through cryomilling, degassing, hot isostatic pressing and extrusion, followed by a subsequent heat treatment. The mechanical behavior and microstructure of the materials were analyzed and compared directly to the coarse-grained (CG) counterpart. Three-dimensional atom-probe tomography was utilized to investigate the intermetallic precipitates and oxide dispersoids formed in the as-extruded UFG material. UFG 7075 exhibits higher strength than the CG 7075 alloy for each equivalent condition. After a T6 Temper, the yield strength (YS) and ultimate tensile strength (UTS) of UFG 7075 achieved 734 and 774 MPa, respectively, which are ∼120 MPa higher than those of the CG equivalent. The strength of as-extruded UFG 7075 (YS: 583 MPa, UTS: 631 MPa) is even higher than that of commercial 7075-T6. More importantly, the strengthening mechanisms in each material were established quantitatively for the first time for this complex precipitation-strengthened system, accounting for grain-boundary, dislocation, solid-solution, precipitation and oxide dispersoid strengthening contributions. Grain-boundary strengthening was the predominant mechanism in as-extruded UFG 7075, contributing a strength increment estimated to be 242 MPa, whereas Orowan precipitation strengthening was predominant in the as-extruded CG 7075 (∼102 MPa) and in the T6-Tempered materials, and was estimated to contribute 472 and 414 MPa for CG-T6 and UFG-T6, respectively.

Haiming Wen - One of the best experts on this subject based on the ideXlab platform.

  • Atom-Probe Tomographic Study of Precipitation in an Ultrafine-grained Al-Zn-Mg- Cu Alloy (Al 7075)
    2016
    Co-Authors: Julie M. Schoenung, Haiming Wen, Dieter Isheim, David N Seidman, E J Lavernia, David Seidman, Enrique J
    Abstract:

    Precipitation-hardened alloys can be further strengthened by reducing the grain size down to the ultrafine regime (<1 μm) and thereby incorporating significant grain boundary (GB) strengthening [1, 2]. The ultrafine-grained (UFG) structure is expected to induce an influence on the precipitation behavior, because of the significantly reduced length scale. Nevertheless, there have been very limited studies on the effect of length scale on precipitation [3]. The present study was undertaken to obtain quantitative information on the differences in precipitation behavior between UFG structure and the traditional coarse-grained (CG) counterpart, and to provide fundamental insights into the underlying mechanisms. Al 7075 alloy, with major alloying elements of Zn, Mg and Cu, was selected for study because of its technological importance and the existing extensive studies on precipitation phenomena in CG Al 7075. An UFG Al 7075 alloy was fabricated via powder cryomilling, degassing, hot isostatic pressing and extrusion, followed by solution treatment and artificial aging (T6 Temper); a CG counterpart was prepared from unmilled CG powders using the same degassing, consolidation and heat treatment rout

  • Cu Alloy (Al 7075)
    2016
    Co-Authors: David N Seidman, Julie M. Schoenung, Haiming Wen, Dieter Isheim, E J Lavernia, David Seidman, See Profile, Enrique J
    Abstract:

    Precipitation-hardened alloys can be further strengthened by reducing the grain size down to the ultrafine regime (<1 μm) and thereby incorporating significant grain boundary (GB) strengthening [1, 2]. The ultrafine-grained (UFG) structure is expected to induce an influence on the precipitation behavior, because of the significantly reduced length scale. Nevertheless, there have been very limited studies on the effect of length scale on precipitation [3]. The present study was undertaken to obtain quantitative information on the differences in precipitation behavior between UFG structure and the traditional coarse-grained (CG) counterpart, and to provide fundamental insights into the underlying mechanisms. Al 7075 alloy, with major alloying elements of Zn, Mg and Cu, was selected for study because of its technological importance and the existing extensive studies on precipitation phenomena in CG Al 7075. An UFG Al 7075 alloy was fabricated via powder cryomilling, degassing, hot isostatic pressing and extrusion, followed by solution treatment and artificial aging (T6 Temper); a CG counterpart was prepared from unmilled CG powders using the same degassing, consolidation and heat treatment route [3]. The precipitation behavior in the UFG alloy was studied by atom-probe tomography (APT) an

  • mechanical behavior and strengthening mechanisms in ultrafine grain precipitation strengthened aluminum alloy
    Acta Materialia, 2014
    Co-Authors: Haiming Wen, Troy D Topping, Dieter Isheim, David N Seidman, E J Lavernia, Julie M. Schoenung
    Abstract:

    To provide insight into the relationships between precipitation phenomena, grain size and mechanical behavior in a complex precipitation-strengthened alloy system, Al 7075 alloy, a commonly used aluminum alloy, was selected as a model system in the present study. Ultrafine-grained (UFG) bulk materials were fabricated through cryomilling, degassing, hot isostatic pressing and extrusion, followed by a subsequent heat treatment. The mechanical behavior and microstructure of the materials were analyzed and compared directly to the coarse-grained (CG) counterpart. Three-dimensional atom-probe tomography was utilized to investigate the intermetallic precipitates and oxide dispersoids formed in the as-extruded UFG material. UFG 7075 exhibits higher strength than the CG 7075 alloy for each equivalent condition. After a T6 Temper, the yield strength (YS) and ultimate tensile strength (UTS) of UFG 7075 achieved 734 and 774 MPa, respectively, which are ∼120 MPa higher than those of the CG equivalent. The strength of as-extruded UFG 7075 (YS: 583 MPa, UTS: 631 MPa) is even higher than that of commercial 7075-T6. More importantly, the strengthening mechanisms in each material were established quantitatively for the first time for this complex precipitation-strengthened system, accounting for grain-boundary, dislocation, solid-solution, precipitation and oxide dispersoid strengthening contributions. Grain-boundary strengthening was the predominant mechanism in as-extruded UFG 7075, contributing a strength increment estimated to be 242 MPa, whereas Orowan precipitation strengthening was predominant in the as-extruded CG 7075 (∼102 MPa) and in the T6-Tempered materials, and was estimated to contribute 472 and 414 MPa for CG-T6 and UFG-T6, respectively.

E J Lavernia - One of the best experts on this subject based on the ideXlab platform.

  • Atom-Probe Tomographic Study of Precipitation in an Ultrafine-grained Al-Zn-Mg- Cu Alloy (Al 7075)
    2016
    Co-Authors: Julie M. Schoenung, Haiming Wen, Dieter Isheim, David N Seidman, E J Lavernia, David Seidman, Enrique J
    Abstract:

    Precipitation-hardened alloys can be further strengthened by reducing the grain size down to the ultrafine regime (<1 μm) and thereby incorporating significant grain boundary (GB) strengthening [1, 2]. The ultrafine-grained (UFG) structure is expected to induce an influence on the precipitation behavior, because of the significantly reduced length scale. Nevertheless, there have been very limited studies on the effect of length scale on precipitation [3]. The present study was undertaken to obtain quantitative information on the differences in precipitation behavior between UFG structure and the traditional coarse-grained (CG) counterpart, and to provide fundamental insights into the underlying mechanisms. Al 7075 alloy, with major alloying elements of Zn, Mg and Cu, was selected for study because of its technological importance and the existing extensive studies on precipitation phenomena in CG Al 7075. An UFG Al 7075 alloy was fabricated via powder cryomilling, degassing, hot isostatic pressing and extrusion, followed by solution treatment and artificial aging (T6 Temper); a CG counterpart was prepared from unmilled CG powders using the same degassing, consolidation and heat treatment rout

  • Cu Alloy (Al 7075)
    2016
    Co-Authors: David N Seidman, Julie M. Schoenung, Haiming Wen, Dieter Isheim, E J Lavernia, David Seidman, See Profile, Enrique J
    Abstract:

    Precipitation-hardened alloys can be further strengthened by reducing the grain size down to the ultrafine regime (<1 μm) and thereby incorporating significant grain boundary (GB) strengthening [1, 2]. The ultrafine-grained (UFG) structure is expected to induce an influence on the precipitation behavior, because of the significantly reduced length scale. Nevertheless, there have been very limited studies on the effect of length scale on precipitation [3]. The present study was undertaken to obtain quantitative information on the differences in precipitation behavior between UFG structure and the traditional coarse-grained (CG) counterpart, and to provide fundamental insights into the underlying mechanisms. Al 7075 alloy, with major alloying elements of Zn, Mg and Cu, was selected for study because of its technological importance and the existing extensive studies on precipitation phenomena in CG Al 7075. An UFG Al 7075 alloy was fabricated via powder cryomilling, degassing, hot isostatic pressing and extrusion, followed by solution treatment and artificial aging (T6 Temper); a CG counterpart was prepared from unmilled CG powders using the same degassing, consolidation and heat treatment route [3]. The precipitation behavior in the UFG alloy was studied by atom-probe tomography (APT) an

  • coupling of dislocations and precipitates impact on the mechanical behavior of ultrafine grained al zn mg alloys
    Acta Materialia, 2016
    Co-Authors: Hanry Yang, E J Lavernia, Troy D Topping, Ali Yousefiani, Julie M. Schoenung
    Abstract:

    Abstract Intragranular coupling of dislocations and precipitates is accomplished in an ultrafine grained aluminum 7000 series alloy through a unique thermo-mechanical processing route that involves high strain rate extrusion at ambient Temperature as the last step. The as-extruded materials also exhibited a unique bimodal microstructure consisting of: (1) elongated lamellar grains with dimensions of ∼1 μm consisting of sub-grains via low angle grain boundaries, and (2) ultrafine grains approximately ∼100 nm in size with high angle grain boundaries. Our investigation shows that coupling of dislocations and precipitates within the ultrafine grains has a beneficial impact on the mechanical behavior, and results in an extremely high strength, i.e., ultimate tensile strength ∼878 MPa, with uniform elongation of 4.1% strain at fracture. Interestingly, the T6 Temper leads to a decrease in strength for the ultrafine grained material with intragranular dislocations while it enhances ductility, which is opposite the behavior observed in the ultrafine grained material that does not contain a high density of intragranular dislocations. This phenomenon is attributed to the loss in dislocation strengthening and grain boundary strengthening, which could not be compensated for by the strength increase due to precipitation. The underlying mechanisms are discussed on the basis of in-situ heating in a transmission electron microscope, theoretical analysis of diffusion controlled precipitation and microstructure characterization, including transmission Kikuchi diffraction.

  • mechanical behavior and strengthening mechanisms in ultrafine grain precipitation strengthened aluminum alloy
    Acta Materialia, 2014
    Co-Authors: Haiming Wen, Troy D Topping, Dieter Isheim, David N Seidman, E J Lavernia, Julie M. Schoenung
    Abstract:

    To provide insight into the relationships between precipitation phenomena, grain size and mechanical behavior in a complex precipitation-strengthened alloy system, Al 7075 alloy, a commonly used aluminum alloy, was selected as a model system in the present study. Ultrafine-grained (UFG) bulk materials were fabricated through cryomilling, degassing, hot isostatic pressing and extrusion, followed by a subsequent heat treatment. The mechanical behavior and microstructure of the materials were analyzed and compared directly to the coarse-grained (CG) counterpart. Three-dimensional atom-probe tomography was utilized to investigate the intermetallic precipitates and oxide dispersoids formed in the as-extruded UFG material. UFG 7075 exhibits higher strength than the CG 7075 alloy for each equivalent condition. After a T6 Temper, the yield strength (YS) and ultimate tensile strength (UTS) of UFG 7075 achieved 734 and 774 MPa, respectively, which are ∼120 MPa higher than those of the CG equivalent. The strength of as-extruded UFG 7075 (YS: 583 MPa, UTS: 631 MPa) is even higher than that of commercial 7075-T6. More importantly, the strengthening mechanisms in each material were established quantitatively for the first time for this complex precipitation-strengthened system, accounting for grain-boundary, dislocation, solid-solution, precipitation and oxide dispersoid strengthening contributions. Grain-boundary strengthening was the predominant mechanism in as-extruded UFG 7075, contributing a strength increment estimated to be 242 MPa, whereas Orowan precipitation strengthening was predominant in the as-extruded CG 7075 (∼102 MPa) and in the T6-Tempered materials, and was estimated to contribute 472 and 414 MPa for CG-T6 and UFG-T6, respectively.

Ziqiao Zheng - One of the best experts on this subject based on the ideXlab platform.

  • improving the intergranular corrosion resistance of al mg si cu alloys without strength loss by a two step aging treatment
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2014
    Co-Authors: Zhixiu Wang, Hai Li, Fenfen Miao, Bijun Fang, Renguo Song, Ziqiao Zheng
    Abstract:

    Abstract In order to improve the intergranular corrosion (IGC) resistance of Al–Mg–Si–Cu alloys without strength loss compared to that of the T6 Temper, a new two-step aging treatment has been developed in the present study. The two-step aging treatment includes pre-aging at a relatively higher Temperature for a shorter time and then re-aging at a lower Temperature for a relatively longer time. The microstructural observation shows that after the optimized two-step aging of 180 °C/2 h+160 °C/120 h, the microstructural characteristics of the alloy combines the matrix of high number density β″ precipitates and grain boundaries of discretely distributed GBPs. The type of microstructures is responsible for the improvement of IGC resistance of the alloy without strength loss.

Troy D Topping - One of the best experts on this subject based on the ideXlab platform.

  • coupling of dislocations and precipitates impact on the mechanical behavior of ultrafine grained al zn mg alloys
    Acta Materialia, 2016
    Co-Authors: Hanry Yang, E J Lavernia, Troy D Topping, Ali Yousefiani, Julie M. Schoenung
    Abstract:

    Abstract Intragranular coupling of dislocations and precipitates is accomplished in an ultrafine grained aluminum 7000 series alloy through a unique thermo-mechanical processing route that involves high strain rate extrusion at ambient Temperature as the last step. The as-extruded materials also exhibited a unique bimodal microstructure consisting of: (1) elongated lamellar grains with dimensions of ∼1 μm consisting of sub-grains via low angle grain boundaries, and (2) ultrafine grains approximately ∼100 nm in size with high angle grain boundaries. Our investigation shows that coupling of dislocations and precipitates within the ultrafine grains has a beneficial impact on the mechanical behavior, and results in an extremely high strength, i.e., ultimate tensile strength ∼878 MPa, with uniform elongation of 4.1% strain at fracture. Interestingly, the T6 Temper leads to a decrease in strength for the ultrafine grained material with intragranular dislocations while it enhances ductility, which is opposite the behavior observed in the ultrafine grained material that does not contain a high density of intragranular dislocations. This phenomenon is attributed to the loss in dislocation strengthening and grain boundary strengthening, which could not be compensated for by the strength increase due to precipitation. The underlying mechanisms are discussed on the basis of in-situ heating in a transmission electron microscope, theoretical analysis of diffusion controlled precipitation and microstructure characterization, including transmission Kikuchi diffraction.

  • mechanical behavior and strengthening mechanisms in ultrafine grain precipitation strengthened aluminum alloy
    Acta Materialia, 2014
    Co-Authors: Haiming Wen, Troy D Topping, Dieter Isheim, David N Seidman, E J Lavernia, Julie M. Schoenung
    Abstract:

    To provide insight into the relationships between precipitation phenomena, grain size and mechanical behavior in a complex precipitation-strengthened alloy system, Al 7075 alloy, a commonly used aluminum alloy, was selected as a model system in the present study. Ultrafine-grained (UFG) bulk materials were fabricated through cryomilling, degassing, hot isostatic pressing and extrusion, followed by a subsequent heat treatment. The mechanical behavior and microstructure of the materials were analyzed and compared directly to the coarse-grained (CG) counterpart. Three-dimensional atom-probe tomography was utilized to investigate the intermetallic precipitates and oxide dispersoids formed in the as-extruded UFG material. UFG 7075 exhibits higher strength than the CG 7075 alloy for each equivalent condition. After a T6 Temper, the yield strength (YS) and ultimate tensile strength (UTS) of UFG 7075 achieved 734 and 774 MPa, respectively, which are ∼120 MPa higher than those of the CG equivalent. The strength of as-extruded UFG 7075 (YS: 583 MPa, UTS: 631 MPa) is even higher than that of commercial 7075-T6. More importantly, the strengthening mechanisms in each material were established quantitatively for the first time for this complex precipitation-strengthened system, accounting for grain-boundary, dislocation, solid-solution, precipitation and oxide dispersoid strengthening contributions. Grain-boundary strengthening was the predominant mechanism in as-extruded UFG 7075, contributing a strength increment estimated to be 242 MPa, whereas Orowan precipitation strengthening was predominant in the as-extruded CG 7075 (∼102 MPa) and in the T6-Tempered materials, and was estimated to contribute 472 and 414 MPa for CG-T6 and UFG-T6, respectively.