Strengthening mechanisms in aluminum containing coherent Al3Sc precipitates and incoherent Al2O3 dispersoids

Karnesky, Richard A.; Meng, Liang; Dunand, David C.

doi:10.1016/j.actamat.2006.10.004

Cited by 82 publications

(53 citation statements)

References 44 publications

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“…The much lower diffusivity of Zr compared to Sc in aluminum helps to stabilize the Al 3 (Sc, Zr) precipitates up to at least 350°C. [11][12][13][14] Therefore, by adding Zr and Sc in combination, a dense and homogeneous distribution of thermally stable Al 3 (Sc, Zr) precipitates is obtained during annealing. [11] Zinc has good solid solubility and can form precipitates under appropriate conditions, allowing both solid solution strengthening and precipitation strengthening.…”

Section: Introductionmentioning

confidence: 98%

Effect of Sc and Zn Additions on Microstructure and Hot Formability of Al-Mg Sheet Alloys

Zhu

Dahle

Ghosh

2009

Metall Mater Trans A

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Trace elements of Sc or Zn were added to Al-Mg sheet alloys. Microstructural examination showed that the Sc addition greatly refined the grain size, especially in the Zn-containing alloy where large amounts of subgrains and fine grains were formed. Meanwhile, a number of large primary intermetallic particles formed in the Sc-adding alloys. In order to evaluate the hightemperature formability, warm tensile tests were carried out at temperatures ranging from 275°C to 350°C and at strain rates of 0.015 to 1.5 s À1 . The test results showed that, in the alloys with the single addition of Zn or Sc, Zn slightly increased the flow stress but decreased the ductility and Sc worsened both the flow stress and the ductility. However, in the alloy with the combined addition of Zn and Sc, the flow stress was significantly increased at almost all testing conditions and the ductility was also increased at a higher temperature of 350°C and lower strain rate of 0.015 s À1 . The results of superplastic tensile tests and biaxial stretch tests demonstrated that the alloy with both Zn and Sc additions exhibited good high-temperature formability. The effect of Zn and Sc additions on the microstructure and the hot formability is discussed.

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Section: Introductionmentioning

confidence: 98%

Effect of Sc and Zn Additions on Microstructure and Hot Formability of Al-Mg Sheet Alloys

Zhu

Dahle

Ghosh

2009

Metall Mater Trans A

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“…This situation occurs when the dislocations are pinned at the departure side of the coarse precipitates, while concurrently subjected to the elastic back-stress from 8 neighboring fine precipitates. The overall threshold stress is the sum of the true detachment stress from the precipitates and the back-stress [22]. As it is noticed in the above discussion, the combination of work strengthening and precipitation strengthening provides excellent strength to the alloy after pre-stretching and subsequent aging treatment.…”

Section: Effect Of Pre-stretching On the Mechanical Propertiesmentioning

confidence: 98%

Enhanced Age Strengthening of Mg-Nd-Zn-Zr Alloy via Pre-Stretching

Guo

Zhao

Wang

et al. 2016

Metals

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Pre-stretching was carried out to modify the microstructure of Mg-Nd-Zn-Zr alloy to enhance its age strengthening. The results indicated that more heterogeneous nucleation sites can be provided by the high density of dislocations caused by the plastic pre-stretching deformation, as well as speeding up the growth rate of precipitates. Comparison of microstructure in non-pre-stretched specimens after artificial aging showed that pre-stretched specimens exhibited a higher number density of precipitates. The fine and coarse plate-shaped precipitates were found in the matrix. Due to an increase in the number density of precipitates, the dislocation slipping during the deformation process is effectively hindered, and the matrix is strengthened. The yield strength stabilizes at 4% pre-stretching condition, and then the evolution is stable within the error bars. The 8% pre-stretched specimens can achieve an ultimate tensile strength of 297 MPa. However, further pre-stretching strains after 8% cannot supply any increase in strength. Tensile fracture surfaces of specimens subjected to pre-stretching strain mainly exhibit a trans-granular cleavage fracture. This work indicated that a small amount of pre-stretching strain can further increase strength of alloy and also effectively enhance the formation of precipitates, which can expand the application fields of this alloy.

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“…The ambient-temperature strength can be generally explained and predicted by classical precipitate shearing and Orowan bypassing mechanisms. [10,17,21,30,32,34] It is known that for a precipitate, which has a size smaller than the critical radius and has coherent structure with matrix, the strength is controlled by precipitate shearing, whereas for large precipitate sizes, the Orowan dislocation bypass mechanism controls the strength. At elevated temperature, there is sufficient thermal energy to allow dislocation circumventing the precipitates by climbing.…”

Section: A Strengthening Mechanismsmentioning

confidence: 99%

Mechanical Properties and Strengthening Mechanisms of Al-15 Pct B4C Composites with Sc and Zr at Elevated Temperatures

Qin

Zhang

Chen

2016

Metall Mater Trans A

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The mechanical properties at ambient and elevated temperatures of two Al-15 vol pct B 4 C composites, S40 with 0.4 wt pct Sc and SZ40 with 0.4 wt pct Sc and 0.24 wt pct Zr, are investigated during long-term thermal annealing. The presence of large B 4 C particles in the microscale has a moderate but stable strengthening effect on Al-B 4 C composites at ambient and elevated temperatures, while the precipitation of nanoscale Al 3 Sc and Al 3 (Sc, Zr) in the composite matrix provides a predominate contribution to the composite strength, which is varied by tested temperatures. The Al 3 Sc precipitates in S40 remain coarsening resistant at 523 K (250°C), whereas the Al 3 (Sc, Zr) precipitates in SZ40 are thermally stable at 573 K (300°C) over 2000 hours of annealing. At higher annealing temperatures (573 K (300°C) for S40 and 623 K (350°C) for SZ40), both Al 3 Sc and Al 3 (Sc, Zr) precipitates become coarsening with prolonged annealing time. The yield strength of S40 and SZ40 at ambient temperature decreases with the increasing precipitate size, which can be explained by the classical precipitate shearing and Orowan bypass mechanisms. At elevated temperatures [523 K to 623 K (250°C to 350°C)], considerably lower yield stresses are observed compared to those at ambient temperature, which invokes a dislocation climb mechanism. The predicted yield strengths at elevated temperatures by the combination of dislocation climb and Orowan models are in good agreement with the experimental data.

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Strengthening mechanisms in aluminum containing coherent Al3Sc precipitates and incoherent Al2O3 dispersoids

Cited by 82 publications

References 44 publications

Effect of Sc and Zn Additions on Microstructure and Hot Formability of Al-Mg Sheet Alloys

Effect of Sc and Zn Additions on Microstructure and Hot Formability of Al-Mg Sheet Alloys

Enhanced Age Strengthening of Mg-Nd-Zn-Zr Alloy via Pre-Stretching

Mechanical Properties and Strengthening Mechanisms of Al-15 Pct B4C Composites with Sc and Zr at Elevated Temperatures

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