The Effect of Aluminium Content on the Mechanical Properties and Microstructure of Die Cast Binary Magnesium-Aluminium Alloys

Dargusch, Matthew S.; Pettersen, Ketil; Nogita, Kazuhiro; Nave, Mark; Dunlop, G. L.

doi:10.2320/matertrans.47.977

Cited by 54 publications

(20 citation statements)

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“…The proportion of coarse grains at the core appeared to be related to the alloy's solidification range, and reached a maximum also for the alloy with 5.51 mass% Al. The degree of bimodality of the grain populations at the core and surface, portioned according to statistical techniques, was maximum for the alloy with 5.51 mass% Al.Despite the large amount of effort devoted to relate the tensile properties to the solidification structure of high pressure diecast (hpdc) magnesium (Mg) alloys, [1][2][3][4][5][6][7][8][9][10][11][12][13][14] little systematic work has been reported on how the grain microstructure is affected by the solute content. This is important for two reasons.…”

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“…The other refers to the non-uniformity of the grain structure which characterises hpdc. The small grain sizes near the surface of the castings are usually considered to dominate the strength [3,4,[6][7][8][14][15][16][17] through a strong Hall-Petch effect. However, as discussed thoroughly by Kurzydlowski and Bucki, [18] a mixture of grain sizes on the specimen cross-section may actually lead to an overall softening, and generally affect the flow behaviour.…”

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Solute Content and the Grain Microstructure of High Pressure Diecast Magnesium–Aluminium Alloys

2009

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Seven binary alloys, with Al contents from 0.47 to 11.6 mass%, have been studied using electron back scattered diffraction. Grain size measurements were made at two opposing surface locations and at the core of the castings cross-sections. The alloy with 0.47 mass% Al showed a uniform microstructure of relatively large grains over the entire cross section, whereas higher Al content alloys showed an increasingly bimodal, non-uniform grain structure, with mostly fine grains near the surfaces and mixed fine and coarse grains at the core. The average grain size at the surfaces decreased for solute contents of up to 5.51 mass% Al. No further grain refining was observed for higher solute contents. The average size, d, of the surface grains was found to fit the relationship, d ¼ a þ b = Q , where Q is the growth restriction factor imposed by the solute and a and b are constants. The proportion of coarse grains at the core appeared to be related to the alloy's solidification range, and reached a maximum also for the alloy with 5.51 mass% Al. The degree of bimodality of the grain populations at the core and surface, portioned according to statistical techniques, was maximum for the alloy with 5.51 mass% Al.Despite the large amount of effort devoted to relate the tensile properties to the solidification structure of high pressure diecast (hpdc) magnesium (Mg) alloys, [1][2][3][4][5][6][7][8][9][10][11][12][13][14] little systematic work has been reported on how the grain microstructure is affected by the solute content. This is important for two reasons. One is whether grain nucleation and growth in hpdc is controlled by the solute concentration as in quiescent castings. The other refers to the non-uniformity of the grain structure which characterises hpdc. The small grain sizes near the surface of the castings are usually considered to dominate the strength [3,4,[6][7][8][14][15][16][17] through a strong Hall-Petch effect. However, as discussed thoroughly by Kurzydlowski and Bucki, [18] a mixture of grain sizes on the specimen cross-section may actually lead to an overall softening, and generally affect the flow behaviour. Therefore, an accurate description of the distribution of grain sizes over the casting's cross-section for different solute contents is necessary in order to both quantify the Hall-Petch contribution to the overall strengthening, and understand the way MgÀAl alloys yield plastically.The region near the surface of the casting cross-section normally contains a predominantly fine grain structure, while the centre, or 'core', includes a large fraction of coarse grains. [4,15,19] This bimodal grain structure is thought to be formed through two main processes: [10,20,21] the small grains near the surface result from the fast solidification rate inherent to the hpdc process, and are thus related to the so-called 'skin effect'; [4,6,7,15,16,19] the large grains, sitting mainly at the core, are normally ascribed to the formation of crystals through partial solidification in the shot sleeve, which are injected in...

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Solute Content and the Grain Microstructure of High Pressure Diecast Magnesium–Aluminium Alloys

2009

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“…[46][47][48] In alloys containing a ductile primary phase, the strain hardening is related to the volume fraction and modulus of the dispersed particles for strains lower than 1 pct. [47] The role of intermetallic phases in strengthening has been verified in die-cast Mg-Al [49,50] and Mg-RE [36] binary alloys, in which the yield strength showed a monotonic increase with increasing content of the alloying element. Furthermore, a good correlation between the yield strength and the amount of intermetallic phase was observed in binary Mg-RE alloys.…”

Section: A Microstructure/tensile Properties Relationshipmentioning

confidence: 99%

Evaluation of Magnesium Die-Casting Alloys for Elevated Temperature Applications: Microstructure, Tensile Properties, and Creep Resistance

Zhu

Easton

Abbott³

et al. 2015

Metall Mater Trans A

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128

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Several families of magnesium die-casting alloys have been developed to operate at the elevated temperatures experienced in automotive powertrain applications. Most alloys are based on the Mg-Al system with alloying additions such as silicon, strontium, calcium, and rare earth elements (RE), although alloys with RE as the primary alloying constituent are also considered. This work presents an evaluation of the tensile properties and creep resistance of the most common magnesium die-casting alloys, in conjunction with the analysis of microstructure. The alloys investigated include AS31 (Mg-3Al-1Si), AJ52 (Mg-5Al-2Sr), MRI153A (Mg-9Al-1Ca-0.1Sr), MRI153M (Mg-8Al-1Ca-0.3Sr), MRI230D (Mg-6.5Al-2Ca-1Sn-0.3Sr), AXJ530 (Mg5Al-3Ca-0.2Sr), AE42 (Mg-4Al-2RE), AE44 (Mg-4Al-4RE), and AM-HP2+ (Mg-3.5RE-0.4Zn). It is shown that, among the various alloys evaluated, MRI230D, AXJ530, and AM-HP2+ have higher yield strength than the Al alloy A380, but the ductility is relatively low at room temperature for these alloys. In contrast, AS31 and the AE series alloys have very good room temperature ductility, but their yield strength is lower than that of A380. In terms of creep resistance, MRI230D, AXJ530, AE44, and AM-HP2+ are all comparable to the Al alloy counterpart at 423 K and 448 K (150°C and 175°C). Microstructural factors that are most important to the strength and creep resistance of the Mg die-casting alloys are discussed.

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“…Carbon based additions have shown significant refinement but it causes environmental pollution while boron addition is maintained longer and is considered more feasible [8]. The effect of aluminium content on microstructure of Mg-Al alloys has been studied by Dargusch et al [9] and the effect of boron addition on grain refinement of AZ91 alloy has been studied by Suresh et al [5]. In this research, we do a comparative study of addition of boron based master alloy Al-5B and equivalent solute addition in form of Al to the grain refinement of AZ91D alloy.…”

Section: Introductionmentioning

confidence: 99%

Effect of Al Addition on Microstructure of AZ91D

Joshi¹,

Babu²

2014

Magnesium Technology 2014

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Casting is a net shape or near net shape forming process so workhardening will not be applicable for improving properties of magnesium cast alloys. Grain refinement, solid-solution strengthening, precipitation hardening and specially designed heat treatment are the techniques used to enhance the properties of these alloys. This research focusses on grain refinement of magnesium alloy AZ91D, which is a widely used commercial cast alloy. Recently, Al-B based master alloys have shown potential in grain refining AZ91D. A comparative study of the grain refinement of AZ91D by addition of 0.02wt%B, 0.04wt%B, 0.1wt%B, 0.5wt%B and 1.0wt%B of Al-5B master alloy and equivalent amount of solute element aluminium is described in this paper. Hardness profile of AZ91D alloyed with boron and aluminium is compared.

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The Effect of Aluminium Content on the Mechanical Properties and Microstructure of Die Cast Binary Magnesium-Aluminium Alloys

Cited by 54 publications

References 6 publications

Solute Content and the Grain Microstructure of High Pressure Diecast Magnesium–Aluminium Alloys

Solute Content and the Grain Microstructure of High Pressure Diecast Magnesium–Aluminium Alloys

Evaluation of Magnesium Die-Casting Alloys for Elevated Temperature Applications: Microstructure, Tensile Properties, and Creep Resistance

Effect of Al Addition on Microstructure of AZ91D

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