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P B Prangnell - One of the best experts on this subject based on the ideXlab platform.

  • the effect of mn and zr Dispersoid forming additions on recrystallization resistance in al cu li aa2198 sheet
    Acta Materialia, 2014
    Co-Authors: Dimitrios Tsivoulas, P B Prangnell
    Abstract:

    Abstract The influence of sole and joint Zr and Mn additions on the recrystallization behaviour of an AA2198-base alloy has been compared during extended annealing at 535 °C, following hot rolling to sheet. With a constant Zr level recrystallization resistance was seen to diminish with the addition of Mn and became progressively worse with a decrease in Zr content, as more Mn was added. It has been found that this behaviour arises because the additional pinning pressure of Al 20 Cu 2 Mn 3 Dispersoids does not adequately compensate for the expansion in width of the Al 3 Zr-free bands that occurs on the addition of Mn to the base alloy, even with the same Zr level. The lower potency of Mn, relative to Zr, in inhibiting recrystallization has been attributed to the poorer coherency and higher aspect ratio of the Al 20 Cu 2 Mn 3 Dispersoids, which reduces their Zener pinning pressure by a factor of four relative to that of the Al 3 Zr phase. In addition, the presence of the coarser Al 20 Cu 2 Mn 3 Dispersoids was found to increase the stored energy after hot rolling. The recrystallization mechanism was dependent on the Dispersoid type. The addition of Zr led to the dominance of broad front strain-induced boundary migration (SIBM), whereas the addition of Mn-containing Dispersoids favoured particle-stimulated nucleation (PSN). Texture measurements have verified this observation, with SIBM favouring the growth of recrystallized grains of orientations typical of the deformation texture and PSN promoting the growth of randomly orientated grains during recrystallization.

  • interactions between zirconium and manganese Dispersoid forming elements on their combined addition in al cu li alloys
    Acta Materialia, 2012
    Co-Authors: Dimitrios Tsivoulas, J D Robson, Christophe Sigli, P B Prangnell
    Abstract:

    Abstract The present work aims to clarify the interactions that can occur between Zr and Mn in their role as Dispersoid-forming elements in Al–Cu–Li alloys when they are jointly added to rolled products. A combination of Zr and Mn are used because their opposite microsegregation patterns can potentially increase the uniformity of the Dispersoid pinning pressure, and help prevent recrystallization. It is shown, in the AA2198 base alloy studied, that their combined addition in fact reduced recrystallization resistance. The source of this apparent contradiction has been investigated in detail by examining the behaviour of the Dispersoids they form, Al3Zr and Al20Cu2Mn3, from the as-cast ingot to the final rolled product. The Al3Zr Dispersoids were found to be subtly affected by the presence of Mn, which reduced their number density. The main mechanism responsible is the incorporation of low levels of Zr in Mn-rich particles, which slightly reduces the Zr supersaturation in the matrix. Estimates of the level of matrix Zr loss, and modelling of Dispersoid precipitation, have been used to demonstrate the high level of sensitivity of this effect on the Al3Zr Dispersoid-free band widths present and resultant recrystallization resistance when the alloy is rolled to sheets.

  • effects of combined zr and mn additions on Dispersoid formation and recrystallisation behaviour of aa2198 sheet
    Advanced Materials Research, 2010
    Co-Authors: Dimitrios Tsivoulas, P B Prangnell, Christophe Sigli, Bernard Bes
    Abstract:

    The present paper focuses on the influence of combined additions of Zr and Mn on the recrystallisation resistance of aluminium alloy 2198 sheet. Dual additions of these Dispersoid forming elements have previously been reported to be beneficial for reducing recrystallisation during solution treatment, as they exhibit opposing microsegregation partitioning on solidification. Contrary to expectation, it was found that the addition of Mn, to a standard Zr-containing 2198 sheet material, reduced recrystallisation resistance. The reasons for this behaviour are explored by analysis of the morphology, size, chemistry, and distribution of the Dispersoid families formed, as a function of the Mn and Zr level, traced back to the homogenisation stage.

  • effect of processing route and second phase particles on grain refinement during equal channel angular extrusion
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005
    Co-Authors: Marco Berta, P J Apps, P B Prangnell
    Abstract:

    Abstract The effect of coarse and fine second-phase particles on the formation of ultra-fine grained (UFG) structures have been compared during severe deformation by equal-channel angular extrusion using routes A (no rotation) and B C (+90° rotation). The presence of coarse particles has been found to increase the rate of grain refinement with route A and the homogeneity of the submicron grain structure formed, but appears less effective using route B C . In contrast, the presence of fine Dispersoids inhibits the development of new high-angle grain boundaries and the formation of an UFG structure with both routes. Retardation is far more pronounced with rotation of the sample and the dispersiod-containing alloy processed by route B C contained mainly subgrains. The mechanisms operating in each case are discussed.

  • the effect of Dispersoids on the grain refinement mechanisms during deformation of aluminium alloys to ultra high strains
    Acta Materialia, 2005
    Co-Authors: P J Apps, Marco Berta, P B Prangnell
    Abstract:

    Abstract The effect of fine Dispersoids on the mechanisms and rate of grain refinement has been investigated during the severe deformation of a model aluminium alloy. A binary Al–0.2Sc alloy, containing coherent Al3Sc Dispersoids, of ∼20 nm in diameter and ∼100 nm spacing, has been deformed by equal channel angular extrusion to an effective strain of ten. The resulting deformation structures were quantitatively analysed using high-resolution electron backscattered diffraction orientation mapping, and the results have been compared to those obtained from a single-phase Al–0.13Mg alloy, deformed under identical conditions. The presence of fine, non-shearable, Dispersoids has been found to homogenise slip, retard the formation of a cellular substructure and inhibit the formation of microshear bands during deformation. These factors combine to reduce the rate of high-angle grain boundary generation at low to medium strains and, hence, retard the formation of a submicron grain structure to higher strains during severe deformation.

J D Robson - One of the best experts on this subject based on the ideXlab platform.

  • Dispersoid composition in zirconium containing al zn mg cu aa7010 aluminium alloy
    Social Science Research Network, 2019
    Co-Authors: Alexander Cassell, J D Robson, C P Race, Alexander S Eggeman, T Hashimoto, M Besel
    Abstract:

    Zirconium (Zr) is used in modern aluminum alloys to form Dispersoids that control grain structure. The interaction of these Dispersoids with the alloying elements used to strengthen aluminum remains poorly understood. We have used high resolution imaging and composition analysis via electron microscopy to study the Zr-rich Dispersoids in AA7010, a commercial Al-Zn-Mg-Cu alloy, addressing this knowledge gap. We show that the Dispersoids are not of the ideal Al3Zr stoichiometry, and contain Zn up to approximately 15 at%. Copper also concentrates in the Dispersoids up to approximately 6 at%. Atomistic simulation was used to predict the partitioning, demonstrating favourable substitution of Zn and Cu onto the Al sublattice in the Dispersoid phase, consistent with the measurements. We have also observed larger, facetted Dispersoids, which are not of a phase observed in the binary Al-Zr system. Instead, we have found a previously unreported Dispersoid structure (tI10 Ni4Mo structure type), which we propose is stabilized by the presence of Zn. We have calculated the total loss in Zn and Cu due to partitioning into the Dispersoids. We show this is too small to directly have a detrimental effect on age hardening, but may have a secondary effect in promoting heterogeneous nucleation for undesirable quench induced precipitation.

  • heterogeneous zr solute segregation and al3zr Dispersoid distributions in al cu li alloys
    Acta Materialia, 2015
    Co-Authors: Dimitrios Tsivoulas, J D Robson
    Abstract:

    Abstract During the homogenisation treatment of Al alloys the Al3Zr phase is known to form heterogeneously in interdendritic areas where the Zr supersaturation is low. Several types of clusters were observed in the present Al–Cu–Li alloy. Although some clusters resemble the shape of the θ′-Al2Cu lath-shaped particles, it is explained here that there is no direct nucleation on these particles and neither is Zr contained in them at amounts detectable via TEM-EDX. These planar arrays of Zr Dispersoids were established to form via repeated precipitation on dislocations. Nucleation on dislocations was the dominant mechanism for individual Al3Zr Dispersoids also in the dendrite centre. This was explained on the grounds of the large atomic size misfit between Zr and the Al matrix which leads to segregation of the former atoms to dislocations and was verified experimentally by EDX. It is noteworthy that although Zr did not interact with the θ′ phase, it did so with the equilibrium θ phase and produced two different types of particles, one containing only Zr, and another having both Zr and Mn. It was also seen to be contained within Al20Cu2Mn3 Dispersoids in agreement with previous findings.

  • interactions between zirconium and manganese Dispersoid forming elements on their combined addition in al cu li alloys
    Acta Materialia, 2012
    Co-Authors: Dimitrios Tsivoulas, J D Robson, Christophe Sigli, P B Prangnell
    Abstract:

    Abstract The present work aims to clarify the interactions that can occur between Zr and Mn in their role as Dispersoid-forming elements in Al–Cu–Li alloys when they are jointly added to rolled products. A combination of Zr and Mn are used because their opposite microsegregation patterns can potentially increase the uniformity of the Dispersoid pinning pressure, and help prevent recrystallization. It is shown, in the AA2198 base alloy studied, that their combined addition in fact reduced recrystallization resistance. The source of this apparent contradiction has been investigated in detail by examining the behaviour of the Dispersoids they form, Al3Zr and Al20Cu2Mn3, from the as-cast ingot to the final rolled product. The Al3Zr Dispersoids were found to be subtly affected by the presence of Mn, which reduced their number density. The main mechanism responsible is the incorporation of low levels of Zr in Mn-rich particles, which slightly reduces the Zr supersaturation in the matrix. Estimates of the level of matrix Zr loss, and modelling of Dispersoid precipitation, have been used to demonstrate the high level of sensitivity of this effect on the Al3Zr Dispersoid-free band widths present and resultant recrystallization resistance when the alloy is rolled to sheets.

  • a new model for prediction of Dispersoid precipitation in aluminium alloys containing zirconium and scandium
    Acta Materialia, 2004
    Co-Authors: J D Robson
    Abstract:

    A model has been developed to predict precipitation of ternary Al3(Sc, Zr) Dispersoids in aluminium alloys containing zirconium and scandium. The model is based on the classical numerical method of Kampmann and Wagner, extended to predict precipitation of a ternary phase. The model has been applied to the precipitation of Dispersoids in scandium containing AA7050. The Dispersoid precipitation kinetics and number density are predicted to be sensitive to the scandium concentration, whilst the Dispersoid radius is not. The Dispersoids are predicted to enrich in zirconium during precipitation. Coarsening has been investigated in detail and it has been predicted that a steady-state size distribution is only reached once coarsening is well advanced. The addition of scandium is predicted to eliminate the Dispersoid free zones observed in scandium free 7050, greatly increasing recrystallization resistance.

  • modelling al3zr Dispersoid precipitation in multicomponent aluminium alloys
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2003
    Co-Authors: J D Robson, P B Prangnell
    Abstract:

    Abstract An integrated modelling approach has been used to predict the precipitation of metastable L1 2 Al 3 Zr Dispersoids in multicomponent aluminium alloys, during homogenization heat treatment. The Scheil–Gulliver method has been used to predict the segregation of the alloying elements after casting. A coupled model was then developed to predict the simultaneous precipitation of Al 3 Zr Dispersoids and diffusional redistribution of the alloying elements during subsequent homogenization. The effect of the concentration of copper, magnesium and zinc solute on Dispersoid precipitation has been predicted for 7xxx aluminium alloys. These elements are predicted to accelerate Al 3 Zr precipitation kinetics, with changes in magnesium concentration showing the strongest effect. The effect of the solute concentration on the width of the Dispersoid free zone towards the edge of the dendrites has also been calculated. Increasing solute concentration is predicted to reduce this width, and the possible consequences of this on the fraction of recrystallization have been investigated.

Grant X Chen - One of the best experts on this subject based on the ideXlab platform.

  • improvement in the mechanical properties and creep resistance of al mn mg 3004 alloy with sc and zr addition
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018
    Co-Authors: Zhen Li, Z Zhang, Grant X Chen
    Abstract:

    Abstract Sc and Zr were added to Al-Mn-Mg 3004 alloy to form two populations of strengthening particles (50–70 nm-sized α-Al(Mn,Fe)Si Dispersoids and 6–8 nm-sized Al3(Sc,Zr) precipitates), and their strengthening effects on the mechanical properties and creep resistance at ambient and elevated temperatures were studied. The results showed that the microhardness and yield strength at ambient temperature greatly increased upon the addition of Sc and Zr. The creep resistance at 300 °C significantly improved due to the precipitation of fine Al3(Sc,Zr) particles and reduction of the particle-free zone. However, the yield strength at 300 °C remained constant even though the Sc and Zr content increased. The combined effects of α-Al(Mn,Fe)Si Dispersoids and Al3(Sc,Zr) precipitates on the yield strengths at 25 °C and 300 °C were quantitatively analyzed based on the Orowan bypass and dislocation climb mechanisms. The analytically predicted yield strengths are in good agreement with the experimental data.

  • microstructure elevated temperature mechanical properties and creep resistance of Dispersoid strengthened al mn mg 3xxx alloys with varying mg and si contents
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017
    Co-Authors: Zhen Li, Z Zhang, Grant X Chen
    Abstract:

    Abstract In the present work, the effects of magnesium and silicon addition on microstructure, elevated-temperature yield strength and creep resistance of Al-Mn-Mg 3xxx alloys were investigated. The microstructure evolution under as-cast and heat-treated conditions was quantitatively evaluated by optical and electron microscopy. Results revealed that both magnesium and silicon had an important influence on the distribution and volume fraction of precipitated Dispersoids in 3xxx alloys. Without Mg or Si addition, Dispersoids could hardly form during the precipitation heat treatment; hence, the alloys free of Mg or Si possessed low yield strength and creep resistance at elevated temperature. A significant improvement in elevated-temperature yield strength and creep resistance was obtained over a wide range of Mg (0.5–1.5 wt%) and Si (0.25–1 wt%) content studied due to the precipitation of a large number of Dispersoids. The best combination of yield strength and creep resistance at 300 ℃ was obtained by the alloy containing 1.0 wt% Mg and 0.25 wt% Si with the maximum volume fraction of Dispersoids and the minimum volume fraction of Dispersoid free zone. The effects of Dispersoid strengthening, solid solution strengthening and grain size on yield strength and creep resistance were discussed based on experimental results.

  • effects of two step homogenization on precipitation behavior of al3zr Dispersoids and recrystallization resistance in 7150 aluminum alloy
    Materials Characterization, 2015
    Co-Authors: Gang Zhao, Zhanying Guo, Grant X Chen
    Abstract:

    Abstract The effect of two-step homogenization treatments on the precipitation behavior of Al 3 Zr Dispersoids was investigated by transmission electron microscopy (TEM) in 7150 alloys. Two-step treatments with the first step in the temperature range of 300–400 °C followed by the second step at 470 °C were applied during homogenization. Compared with the conventional one-step homogenization, both a finer particle size and a higher number density of Al 3 Zr Dispersoids were obtained with two-step homogenization treatments. The most effective Dispersoid distribution was attained using the first step held at 300 °C. In addition, the two-step homogenization minimized the precipitate free zones and greatly increased the number density of Dispersoids near dendrite grain boundaries. The effect of two-step homogenization on recrystallization resistance of 7150 alloys with different Zr contents was quantitatively analyzed using the electron backscattered diffraction (EBSD) technique. It was found that the improved Dispersoid distribution through the two-step treatment can effectively inhibit the recrystallization process during the post-deformation annealing for 7150 alloys containing 0.04–0.09 wt.% Zr, resulting in a remarkable reduction of the volume fraction and grain size of recrystallization grains.

  • interaction between molybdenum and manganese to form effective Dispersoids in an al si cu mg alloy and their influence on creep resistance
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015
    Co-Authors: A R Farkoosh, Grant X Chen, Mihriban Pekguleryuz
    Abstract:

    Abstract The present work investigates the effect of adding Mo and Mn to an Al–Si–Cu–Mg alloy on the formation of thermally stable Dispersoids. Mo and Mn in combination formed a large volume fraction of uniformly distributed Dispersoids within the Al matrix, because of the opposite partitioning behavior ( k M o > 1 v s . k M n 1 ) during the non-equilibrium solidification. Mo (without Mn) formed coherent α-Al(Fe,Mo)Si Dispersoids with a BCC lattice, which were mostly located within intradendritic regions. Subsequent addition of Mn increased the amount of the Dispersoids by substituting the Fe atoms. The combined addition also led to a more uniform Dispersoid distribution by eliminating the interdendritic Dispersoid-free zones (DFZs). Consequently, creep resistance in the temperature range of 300–350 °C improved significantly. At 300 °C and 30 MPa, the minimum creep rate decreased, and creep time-to-fracture and strain-to-fracture each increased with increasing Mn up to 0.5 wt%. Further addition of Mn resulted in increased presence of the eutectic intermetallics in the interdendritic regions, which deteriorated the ductility of the alloy leading to a shorter creep-life time.

  • Dispersoid strengthening of a high temperature al si cu mg alloy via mo addition
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015
    Co-Authors: A R Farkoosh, Grant X Chen, Mihriban Pekguleryuz
    Abstract:

    Abstract The influence of Mo addition on the microstructure and mechanical properties of an Al–7Si–0.5Cu–0.3Mg alloy (wt%) was investigated. The Mo-containing alloy exhibited significant improvement in creep resistance over the base alloy. At 300 °C and 30 MPa, the minimum creep rate decreased by 95% while creep time-to-fracture was increased by 2 orders of magnitude, from 50 min to 1500 min. The tensile yield strength at 300 °C was also increased by 25%. These effects were attributed to the formation of novel Al–(Fe,Mo)–Si Dispersoids during solution treatment in the grain interiors (intradendritic regions). Unlike the age-hardening precipitates, which coarsened resulting in loss of strength, these Dispersoids were thermally stable and retained their strengthening effect at 300 °C. TEM investigations showed that the dislocation motions were effectively hindered by these fine Dispersoids, leading to the reduction in the minimum creep rate. The onset of the tertiary creep stage was delayed by postponing the dislocation pile-up at the interdendritic Si particles. It was found that Mo addition suppressed the formation of the brittle plate-like β-Al5FeSi intermetallics and formed a blocky phase in the cast microstructure, which resulted in 34% increase in elongation at 300 °C.

Mihriban Pekguleryuz - One of the best experts on this subject based on the ideXlab platform.

  • interaction between molybdenum and manganese to form effective Dispersoids in an al si cu mg alloy and their influence on creep resistance
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015
    Co-Authors: A R Farkoosh, Grant X Chen, Mihriban Pekguleryuz
    Abstract:

    Abstract The present work investigates the effect of adding Mo and Mn to an Al–Si–Cu–Mg alloy on the formation of thermally stable Dispersoids. Mo and Mn in combination formed a large volume fraction of uniformly distributed Dispersoids within the Al matrix, because of the opposite partitioning behavior ( k M o > 1 v s . k M n 1 ) during the non-equilibrium solidification. Mo (without Mn) formed coherent α-Al(Fe,Mo)Si Dispersoids with a BCC lattice, which were mostly located within intradendritic regions. Subsequent addition of Mn increased the amount of the Dispersoids by substituting the Fe atoms. The combined addition also led to a more uniform Dispersoid distribution by eliminating the interdendritic Dispersoid-free zones (DFZs). Consequently, creep resistance in the temperature range of 300–350 °C improved significantly. At 300 °C and 30 MPa, the minimum creep rate decreased, and creep time-to-fracture and strain-to-fracture each increased with increasing Mn up to 0.5 wt%. Further addition of Mn resulted in increased presence of the eutectic intermetallics in the interdendritic regions, which deteriorated the ductility of the alloy leading to a shorter creep-life time.

  • Dispersoid strengthening of a high temperature al si cu mg alloy via mo addition
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015
    Co-Authors: A R Farkoosh, Grant X Chen, Mihriban Pekguleryuz
    Abstract:

    Abstract The influence of Mo addition on the microstructure and mechanical properties of an Al–7Si–0.5Cu–0.3Mg alloy (wt%) was investigated. The Mo-containing alloy exhibited significant improvement in creep resistance over the base alloy. At 300 °C and 30 MPa, the minimum creep rate decreased by 95% while creep time-to-fracture was increased by 2 orders of magnitude, from 50 min to 1500 min. The tensile yield strength at 300 °C was also increased by 25%. These effects were attributed to the formation of novel Al–(Fe,Mo)–Si Dispersoids during solution treatment in the grain interiors (intradendritic regions). Unlike the age-hardening precipitates, which coarsened resulting in loss of strength, these Dispersoids were thermally stable and retained their strengthening effect at 300 °C. TEM investigations showed that the dislocation motions were effectively hindered by these fine Dispersoids, leading to the reduction in the minimum creep rate. The onset of the tertiary creep stage was delayed by postponing the dislocation pile-up at the interdendritic Si particles. It was found that Mo addition suppressed the formation of the brittle plate-like β-Al5FeSi intermetallics and formed a blocky phase in the cast microstructure, which resulted in 34% increase in elongation at 300 °C.

Knut Marthinsen - One of the best experts on this subject based on the ideXlab platform.

  • controlling grain structure and texture in al mn from the competition between precipitation and recrystallization
    Acta Materialia, 2017
    Co-Authors: Knut Marthinsen, Ke Huang, Kai Zhang, Roland E Loge
    Abstract:

    Abstract The recrystallization behaviour of Al-Mn alloys (AA3xxx series alloys) is affected by randomly distributed Dispersoids present before annealing, by Dispersoids precipitated at grain/subgrain boundaries before the onset of recrystallization, and by Dispersoids concurrently precipitated during recrystallization. In this study, the effects of these three populations of Dispersoids on the recrystallization behaviour of a cold rolled AA3xxx alloy were analysed and compared using four temperature-time paths to different target temperatures. Changing the temperature-time path modifies the extent of recovery, the Dispersoid structures, as well as the absolute recrystallization temperature, which then influences the final grain structure and recrystallization texture. In particular, an in-depth investigation on how different populations of Dispersoids affect the main recrystallization texture components of AA3xxx alloys, i.e., P{011}〈566〉, ND-Cube {001}〈310〉, and Cube {001}〈100〉, has been carried out. The results clearly show that, as compared to isothermal annealing, annealing with more elaborate heating and annealing schedules (temperature-time paths) all lead to increased strength of the P texture component and decreased intensities of both the Cube and ND-rotated Cube texture components. The increase of P texture strength and average grain size is most significant when recrystallization occurs concurrently with precipitation. The controlling mechanisms behind this behaviour and the possibility to use them to tailor the grain structure and texture of similar alloys are further discussed.

  • The Influence of Processing Conditions on Microchemistry and the Softening Behavior of Cold Rolled Al-Mn-Fe-Si Alloys
    MDPI AG, 2016
    Co-Authors: Ning Wang, Ke Huang, Knut Marthinsen
    Abstract:

    Using different homogenization treatments, different initial microchemistry conditions in terms of solid solution levels of Mn, and number densities and sizes of constituents and Dispersoids were achieved in an Al-Mn-Fe-Si model alloy. For each homogenized condition, the microchemistry and microstructure, which further change both during deformation and subsequent annealing, were quantitatively characterized. The influence of the different microchemistries, with special focus on different particle structures (constituents and Dispersoids), on the softening behavior during annealing after cold rolling and the final grain structure has been systematically studied. Time-Temperature-Transformation diagrams with respect to precipitation and recrystallization as a basis for analysis of the degree of concurrent precipitation during back-annealing have been established. Densely distributed fine pre-existing Dispersoids and/or conditions of significant concurrent precipitation strongly slows down recrystallization kinetics and lead to a grain structure of coarse and strongly elongated grains. At the lowest annealing temperatures, recrystallization may even be completely suppressed. In conditions of low number density and coarse pre-existing Dispersoids, and limited additional concurrent precipitation, recrystallization generally results in an even, fine and equi-axed grain structure. Rough calculations of recrystallized grain size, assuming particle stimulated nucleation as the main nucleation mechanism, compare well with experimentally measured grain sizes

  • evolution in microstructure and properties during non isothermal annealing of a cold rolled al mn fe si alloy with different microchemistry states
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015
    Co-Authors: Ke Huang, Olaf Engler, Yanjun Li, Knut Marthinsen
    Abstract:

    The softening behaviour during non-isothermal annealing of a cold-rolled Al–Mn–Fe–Si model alloy was studied as a function of the state of microchemistry, in terms of the solute level of Mn, size and spatial distribution of the Mn-bearing Dispersoids, as well as their temporal evolution. Microchemistry significantly affects the recrystallization microstructure, crystallographic texture as well as the mechanical property of the investigated alloy after non-isothermal annealing. The nucleation and growth of grains with different orientations are strongly dependent on both annealing temperature and microchemistry, in that pre-existing Dispersoids have a less profound effect on retarding recrystallization than Dispersoids forming concurrently during back-annealing. Strong concurrent precipitation suppresses nucleation and retards recrystallization, which finally leads to a coarse and pan-cake shaped grain structure, accompanied by strong P {011}〈566〉 and/or M {113}〈110〉 texture components and a relatively weaker ND-rotated cube {001}〈310〉 component. A refined grain structure with medium strength P and cube {001}〈100〉 components is obtained when the pre-existing Dispersoids are coarser and fewer, and concurrent precipitation is limited. P-oriented grains are less affected by second phase particles and experience a growth advantage at low annealing temperatures (<350 °C), while M-oriented grains appear at higher temperatures. The intensity of the P texture does not necessarily increase with increasing supersaturation of Mn as observed during isothermal annealing, whereas the level of supersaturated Mn promotes the strength of the M texture. The mechanisms behind are discussed.

  • isothermal annealing of cold rolled al mn fe si alloy with different microchemistry states
    Transactions of Nonferrous Metals Society of China, 2014
    Co-Authors: Ke Huang, L I Yanjun, Knut Marthinsen
    Abstract:

    Abstract Microstructural evolution of a cold-rolled Al–Mn–Fe–Si alloy during annealing was studied. Except the as-cast variant, two other different homogenizations were considered, one gave a high density of fine dispersiods providing a considerable Zener drag influencing the softening behavior while the other gave a lower density of coarser Dispersoid structure providing a much smaller drag effect. The gradual microstructural evolutions during annealing for the three variants were captured by interrupting annealing at different time. Effects of microchemistry state on recrystallization kinetics, recrystallized grain structure and texture were characterized by EBSD. It is demonstrated that the actual softening kinetics, final microstructure and texture are a result of delicate balance between processing condition and microchemistry state. Strong concurrent precipitation takes place in the case with high concentration of Mn in solid solution, which suppresses nucleation and retards recrystallization and finally leads to grain structure of coarse elongated grains dominated by a P texture component together with a ND-rotated cube component. On the contrary, when solute content of Mn is low and pre-existing Dispersoids are relatively coarser, faster recrystallization kinetics is exhibited together with an equiaxed grain structure with mainly cube texture.

  • microstructural evolution during isothermal annealing of a cold rolled al mn fe si alloy with different microchemistry states
    Materials Science Forum, 2014
    Co-Authors: Ke Huang, Yanjun Li, Knut Marthinsen
    Abstract:

    In this paper, investigation of the softening behaviour of a supersaturated Al-Mn-Fe-Si alloy during annealing after cold rolling has been carried out. Two different homogenization conditions were considered, of which one gives a condition of a large amount of small pre-existing Dispersoids, i.e. providing a significant static Zener drag, while the other gives a condition where both concurrent precipitation and Dispersoid drag effects are limited. The homogenized samples with different microchemistry states were then cold-rolled to different strains before subsequent annealing at 300 degrees C. The softening and concurrent precipitation behaviours have been monitored by hardness and electrical conductivity measurements respectively, and the microstructural evolution has been characterized by EBSD. It is clearly demonstrated that the actual microchemistry state, i.e. amount of solutes and second-phase particle structures as determined by the homogenization procedure strongly influence the softening behaviour where a fine dispersion of pre-existing Dispersoids together with concurrent precipitation slow down the recrystallization kinetics considerably and give a very coarse and elongated grain structure.