Microstructure and mechanical properties of magnesium containing high volume fractions of yttria dispersoids

Han, Bing; Dunand, David C.

doi:10.1016/s0921-5093(99)00074-x

Cited by 201 publications

(102 citation statements)

References 22 publications

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“…A solution to this processing problem is to apply to magnesium the high-temperature melt infiltration technique used to fabricate creep-resistant DSC-Al. We recently described in a previous publication [9] such a DSC-Mg material containing 30 vol.% of submicron yttria dispersoids, which was found to exhibit very high compressive strength and stiffness at room-temperature.…”

Section: Introductionmentioning

confidence: 99%

Creep of magnesium strengthened with high volume fractions of yttria dispersoids

Han

Dunand

2001

Materials Science and Engineering: A

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Creep experiments were performed on dispersion-strengthened-cast magnesium (DSC-Mg), consisting of unalloyed magnesium with 1 mm grain size containing 30 vol.% of 0.33 mm yttria particles. Strain rates were measured for temperatures between 573 and 723 K at compressive stresses between 7 and 125 MPa. DSC-Mg exhibits outstanding creep strength as compared with other magnesium materials, but is less creep resistant than comparable DSC-Al and other dispersion-strengthened aluminum materials. Two separate creep regimes were observed in DSC-Mg, at low stresses (|B30 MPa), both the apparent stress exponent (n app :2) and the apparent activation energy (Q app :48 kJ mol − 1 ) are low, while at high stresses (|\34 MPa), these parameters are much higher (n app =9-15 and Q app =230-325 kJ mol − 1 ) and increase, respectively, with increasing temperature and stress. The low-stress regime can be explained by an existing model of grain-boundary sliding inhibited by dispersoids at grain-boundaries. The unexpectedly low activation energy (about half the activation energy of grain boundary diffusion in pure magnesium) is interpreted as interfacial diffusion at the Mg/Y 2 O 3 interface. The high-stress regime can be described by dislocation creep with dispersion-strengthening from the interaction of the submicron particles with matrix dislocations. The origin of the threshold stress is discussed in the light of existing dislocation climb, detachment and pile-up models.

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Section: Introductionmentioning

confidence: 99%

Creep of magnesium strengthened with high volume fractions of yttria dispersoids

Han

Dunand

2001

Materials Science and Engineering: A

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“…Similarly, a change in mechanisms with addition of yttrium was observed under dynamic high strain rate experiments [19]. phenomena such as formation of stable yttrium oxides at grain boundaries [43,44,78], increased forest dislocation based hardening [11,20,21,42], or large grain boundary yttria and precipitate denuded zones near the grain boundaries causing material softening.…”

Section: Discussionmentioning

confidence: 81%

“…Evidence for the occurrence of enhanced grain-boundary shearing with addition of yttrium suggests that the diffusion creep must be accompanied by grain-boundary sliding. Moreover, yttrium has a softening effect on the sliding of boundaries which suggests that the experimentally observed high temperature beneficial effects of yttrium addition could be attributed to some other mechanisms or phenomena such as formation of stable yttrium oxides at grain boundaries [43,44,78], increased forest dislocation based hardening [11,20,21,42], or large grain boundary yttria and precipitate denuded zones near the grain boundaries causing material softening. Furthermore, it has been experimentally shown that in aged Mg-Y alloys, due to a supersaturated solid-solution state within the grains, dynamic precipitation (two pseudoequilibrium phases) can occur during creep [18,26,27].…”

Section: E Effect Of Yttrium On the Grain Boundary Slidingmentioning

confidence: 99%

Atomic-scale investigation of creep behavior in nanocrystalline Mg and Mg–Y alloys

2015

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Magnesium (Mg) and its alloys offer great potential for reducing vehicular mass and energy consumption due to their inherently low densities. Historically, widespread applicability has been limited by low strength properties compared to other structural Al-, Ti-and Fe-based alloys. However, recent studies have demonstrated high-specific-strength in a number of nanocrystalline Mg-alloys. Even so, applications of these alloys would be restricted to low-temperature automotive components due to microstructural instability under high temperature creep loading. Hence, this work aims to gain a better understanding of creep and associated deformation behavior of columnar nanocrystalline Mg and Mg-yttrium (Y) (up to 3at.%Y(10wt.%Y)) with a grain size of 5 nm and 10 nm. Using molecular dynamics (MD) simulations, nanocrystalline magnesium with and without local concentrations of yttrium is subjected to constant-stress loading ranging from 0 to 500 MPa at different initial temperatures ranging from 473 to 723 K. In pure Mg, the analyses of the diffusion coefficient and energy barrier reveal that at lower temperatures (i.e., T < ~423K) the contribution of grain boundary diffusion to the overall creep deformation is stronger that the contribution of lattice diffusion. However, at higher temperatures (T > ~423K) lattice diffusion dominates the overall creep behavior. Interestingly, for the first time, we have shown that the(101 ̅ 1), (101 ̅ 2),(101 ̅ 3) and (101 ̅ 6) boundary sliding energy is reduced with the addition of yttrium. This softening effect in the presence of yttrium suggests that the experimentally observed high temperature beneficial effects of yttrium addition is likely to be attributed to some combination of other reported creep strengthening mechanisms or phenomena such as formation of stable yttrium oxides at grain boundaries or increased forest dislocation-based hardening.

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“…The reasonably uniform distribution of AlN and intermetallic nanoparticles as shown in Figure 2(c) can be attributed to (a) minimal gravity-associated segregation due to judicious selection of stirring parameters [21], (b) good wetting of AlN nanoparticles by the alloy matrix [11,[22][23][24], (c) argon gas disintegration of metallic stream [25], and (d) dynamic deposition of composite slurry on substrate followed by hot extrusion. In the nanocomposite, selected area electron diffraction (SAED) in TEM revealed the (a) partial reaction of AlN with the Mg alloy matrix to form Mg 3 N 2 (see Figure 2(c)) and (b) the occurrence of Mg-Zn nanorods (not observed in the monolithic alloy, see Figure 2(d)).…”

Section: Microstructural Characteristics Microstructural Characterizmentioning

confidence: 99%

The Overall Effects of AlN Nanoparticle Addition to Hybrid Magnesium Alloy AZ91/ZK60A

Paramsothy

Chan²,

Kwok³

et al. 2012

Journal of Nanotechnology

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A hybrid magnesium alloy nanocomposite containing AlN nanoparticle reinforcement was fabricated using solidification processing followed by hot extrusion. The nanocomposite exhibited similar grain size to the monolithic hybrid alloy, reasonable AlN and intermetallic nanoparticle distribution, nondominant (0 0 0 2) texture in the longitudinal direction, and 17% higher hardness than the monolithic hybrid alloy. Compared to the monolithic hybrid alloy, the nanocomposite exhibited higher tensile yield strength (0.2% TYS) and ultimate tensile strength (UTS) without significant compromise in failure strain and energy absorbed until fracture (EA) (+5%, +5%, −14% and −10%, resp.). Compared to the monolithic hybrid alloy, the nanocomposite exhibited unchanged compressive yield strength (0.2% CYS) and higher ultimate compressive strength (UCS), failure strain, and EA (+1%, +6%, +24%, and +6%, resp.). The overall effects of AlN nanoparticle addition on the tensile and compressive properties of the hybrid magnesium alloy is investigated in this paper.

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Microstructure and mechanical properties of magnesium containing high volume fractions of yttria dispersoids

Cited by 201 publications

References 22 publications

Creep of magnesium strengthened with high volume fractions of yttria dispersoids

Creep of magnesium strengthened with high volume fractions of yttria dispersoids

Atomic-scale investigation of creep behavior in nanocrystalline Mg and Mg–Y alloys

The Overall Effects of AlN Nanoparticle Addition to Hybrid Magnesium Alloy AZ91/ZK60A

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