Strengthening mechanisms of MgSi alloys

Abstract:Metallic materials have a significant number of applications, among which Al alloys have drawn people's attention due to their low density and high strength. High-strength Al-based alloys, such as 7XXX Al alloys, contain many alloying elements and with high concentration, whose microstructures present casting voids, segregation, dendrites, etc. In this work, a spray deposition method was employed to fabricate an Al-8.31Zn-2.07Mg-2.46Cu-0.12Zr (wt %) alloy with fine structure. The hot deformation behavior of the studied alloy was investigated using a Gleeble 1500 thermal simulator and electron microscopes. The microstructure evolution, variation in the properties, and precipitation behavior were systematically investigated to explore a short process producing an alloy with high property values. The results revealed that the MgZn 2 particles were detected from inside the grain and grain boundary, while some Al 3 Zr particles were inside the grain. An Arrhenius equation was employed to describe the relationship between the flow stress and the strain rate, and the established constitutive equation was that: Figure 7 gives the hardness variations of the hot compressed samples aged at 120 • C fo durations. For the samples after being hot-compressed at strain rates of 1 s −1 and 0.001 s −1 , present the same trend. The initial hardness of compressed samples increased with the hot de temperature. The hardness of the hot-compressed samples increased with the aging time, a kept constant as they were aging at certain temperatures for 15 h.Metals 2017, 7, 299 deformation temperature. The hardness of the hot-compressed samples increased with the and almost kept constant as they were aging at certain temperatures for 15 h. Discussion Constitutive EquationThe constitutive relationships were used to describe the hot deformation behavior. Som are employed to reveal the hot deformation behavior, in which one of the most extended v the hot working constitutive equation is as follows [24]:where ε is the strain rate; A is a material constant which is independent of temperature true stress; Q is the activation energy; R is the gas constant (8.31); and T is the absolute tem (K). At low stress lever (ασ < 0.8):At high stress lever (ασ > 1.2):(σ) σ n F  , β and n are the material constants, α = β/n. Substituting Equations (2) and (3) (4) and (5), respectively, gives:The values of n and β are from the slopes of the lines in ln ε and σ, lnε and ln σ , Discussion Constitutive EquationThe constitutive relationships were used to describe the hot deformation behavior. Som are employed to reveal the hot deformation behavior, in which one of the most extended v the hot working constitutive equation is as follows [24]:where .ε is the strain rate; A is a material constant which is independent of temperature; σ is stress; Q is the activation energy; R is the gas constant (8.31); and T is the absolute tempera At low stress lever (ασ < 0.8):At high stress lever (ασ > 1.2): F(σ) = σ n , β and n are the material constants, α = β/n. Substit...

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“…An increase in yield stress caused by dislocation bypassing η -MgZn 2 particles in the Orowan process is given by [32][33][34]:…”

Section: Discussionmentioning

confidence: 99%

Hot Deformation Behavior of a Spray-Deposited Al-8.31Zn-2.07Mg-2.46Cu-0.12Zr Alloy

Sheng

Lei

Xiao

et al. 2017

Metals

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“…At elevated temperatures, when stress concentration at a second particle is relaxed by diffusion, cavity formation is not enhanced by a second phase. Occurrence of stress concentration at the second phase can be estimated using the critical diffusion length parameter: 15,22,23) when the particle diameter is less than the critical diffusion length, the stress concentration due to the particle can be relaxed by diffusion and no cavities are formed. Because the second phases in the Mg-Ca alloy are located at grain boundaries, the critical diffusion length, Ã GB , can be given by 22,23) …”

Section: Discussionmentioning

confidence: 99%

Tensile Properties of Forged Mg-Al-Zn-Ca Alloy

et al. 2008

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Continuously-casted Mg-9Al-1Zn-1Ca (in mass%) alloy (Mg-Ca alloy) and Mg-9Al-1Zn alloys (Ca-free Mg alloy) were forged at 573 K and their mechanical properties were investigated by tension tests at ambient temperature and 573 K. The forged Mg-Ca alloy showed higher 0.2% proof stress than the forged Ca-free Mg alloy. The high strength for the Mg-Ca alloy was attributed not only to grain refinement by hot forging, but also to the strengthening mechanisms arising from the difference in thermal expansion and geometrical incompatibility between Mg matrix and second phase. The Ca addition decreased the elongation to failure; however, the decrease was reduced for the forged specimens, compared to the unforged specimen. This results from segmentation of the second phases by the hot forging. Also, the forged Mg-Ca alloy showed a large elongation of 284% at 573 K.

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“…During tensile testing, the pin effect of the Mg2Si particles in the grain boundaries keeps them from sliding. The interfaces of the Mg2Sip/matrix belong to an incoherent interface, due to the differences of the crystal structures and the lattice constants [29]. Therefore, local stress concentration should be preferentially generated at the sharp edges and corners of the Mg2Si particles.…”

Section: Strengthening Mechanisms Of the Mg2si Grainsmentioning

confidence: 99%

A Comparative Characterization of the Microstructures and Tensile Properties of As-Cast and Thixoforged in situ AM60B-10 vol% Mg2Sip Composite and Thixoforged AM60B

Zhang

Chen

Cheng

et al. 2015

Metals

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Abstract:The microstructure and tensile properties of the thixoforged in situ Mg2Sip/AM60B composite were characterized in comparison with the as-cast composite and thixoforged AM60B. The results indicate that the morphology of α-Mg phases, the distribution and amount of β phases and the distribution and morphology of Mg2Si particles in thixoforged composite are completely different from those in as-cast composite. The Mg2Si particles block heat transfer and prevent the α-Mg particles from rotation or migration during reheating. Both the thixoforged composite and thixoforged AM60B alloy exhibit virtually no porosity in the microstructure. The thixoforged composite has the highest comprehensive tensile properties (ultimate tensile strength (UTS)) of 209 MPa and an elongation of 10.2%. The strengthening mechanism of the Mg2Si particle is the additive or synergetic effect of combining the load transfer mechanism, the Orowan looping mechanism and the dislocation strengthening mechanism. Among them, the load transfer mechanism is the main mechanism, and the latter two are minor. The particle splitting and interfacial debonding are the main damage patterns of the composite.

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Strengthening mechanisms of MgSi alloys

Cited by 365 publications

References 27 publications

Hot Deformation Behavior of a Spray-Deposited Al-8.31Zn-2.07Mg-2.46Cu-0.12Zr Alloy

Hot Deformation Behavior of a Spray-Deposited Al-8.31Zn-2.07Mg-2.46Cu-0.12Zr Alloy

Tensile Properties of Forged Mg-Al-Zn-Ca Alloy

A Comparative Characterization of the Microstructures and Tensile Properties of As-Cast and Thixoforged in situ AM60B-10 vol% Mg2Sip Composite and Thixoforged AM60B

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