Effects of precipitates on grain size and mechanical properties of AZ31-x%Nd magnesium alloy

doi:10.1016/S1002-0721(14)60093-4

Journal of Rare Earths

Volume 32, Issue 5, May 2014, Pages 451-457

https://doi.org/10.1016/S1002-0721(14)60093-4 Get rights and content

Abstract

The effects of precipitates on grain size and mechanical properties of as-cast AZ31-x%Nd magnesium alloy were investigated, and the affecting mechanism was also discussed. The results indicated that Al₂Nd phase, Al₁₁Nd₃ phase and a few Al-Mn-Nd-Fe phase were formed when adding 0.38 wt.%–1.46 wt.% Nd into AZ31 melt, coarse Al₂Nd transformed into Al₁₁Nd₃ gradually with the increasing of Nd content. Due to structure and size transformation and content increasing of Al-Nd phase, the grain size of AZ31-x%Nd alloy increased firstly, and then decreased with the increment of Nd content. After reaching a minimum value, once again it rose up, provided that Nd content was further increased. The tensile property reached its optimal value when the adding amount of Nd content was 1.05 wt.%, however, adding excessive amount of Nd deteriorated both ultimate strength and elongation of AZ31 alloy.

TEM image (a) and SAED pattern (b) of Al₁₁Nd₃ phase

References (33)

E Aghion et al.
Magnesium alloys development towards the 21st century
Mater. Sci. Forum
(2000)
BL Mordike et al.
Magnesium properties-applications- potential
Mater. Sci. Eng. A
(2001)
IJ Polmear
Magnesium alloys and applications
Mater. Sci. Technol.
(1994)
H Friedrich et al.
Research for a “new age of magnesium” in the automotive industry
J. Mater. Process. Technol.
(2001)
AK Dahle et al.
Development of the as-cast microstructure in magnesium-aluminium alloys
J. Light Met.
(2001)
GY Zhang et al.
Mechanism of effects of rare earths on microstructure and properties at elevated temperature of AZ91 magnesium alloy
J. Rare Earths
(2007)
YZ Lu et al.
Effects of rare earths on the microstructure, properties and fracture behavior of Mg-Al alloys
Mater. Sci. Eng. A
(2000)
XR Zhu et al.
Microstructure and creep behaviour of Mg-12Gd-3Y-1Zn- 0.4Zr alloy
J. Rare Earths
(2013)
Y Yang et al.
Influence of neodymium on high cycle fatigue behavior of die cast AZ91D magnesium alloy
J. Rare Earths
(2010)
JF Fan et al.
Effect of Ca and Y additions on oxidation behavior of magnesium alloys at high temperatures
J. Rare Earths
(2012)

GY Zhang et al.

Ignition-proof mechanism of magnesium alloy added with rare earth La from first-principle study

J. Rare Earths

(2012)

MX Wang et al.

Effect of yttrium and cerium addition on microstructure and mechanical properties of AM50 magnesium alloy

J. Rare Earths

(2007)

K Yu et al.

Mechanism of grain refinement by adding cerium in Mg and Mg alloys

Rare Metal Mater. Eng. (in Chin.)

(2005)

ZD Zhao et al.

Microstructures and mechanical properties of AZ91D alloys with Y addition

Mater. Sci. Eng. A

(2009)

D Qiu et al.

A new approach to designing a grain refiner for Mg casting alloys and its use in Mg–Y-based alloys

Acta Mater.

(2009)

JH Zhang et al.

Effect of Nd on the microstructure, mechanical properties and corrosion behavior of die-cast Mg-4Al-based alloy

J. Alloys Compd.

(2008)

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Recent studies have focused on how to improve its strength and ductility, and it is well documented that the strength of magnesium alloys are directly related to grain size [6]. A reduction in grain size can enhance the ductility of magnesium alloys without sacrificing their strength [7,8], so various potential grain refiners were employed on casting Mg-Al based alloys such as carbon inoculation [9–12], adding alloying elements [13–17] and adding particles etc. The most commonly accepted theory for carbon inoculation on the grain refinement is that Al4C3 act as heterogeneous nuclei for the α-Mg phase during solidification [11].
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Similar to the matrix part in Fig. 7(a), there are precipitates about 100 nm uniformly dispersed in the matrix of the PyC-Cf/AZ31 composite (Fig. 10). It is generally accepted that the fine and uniform precipitates are benefit to the mechanical property of Mg-Al alloys due to the dispersion strengthening [48,56–58]. According to the rule of mixture, the enhancing of the matrix would contribute to the strengthening of composite.
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: Foundation item: Project supported by Liaoning BaiQianWan Talents Program (2011921065)

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Effects of precipitates on grain size and mechanical properties of AZ31-x%Nd magnesium alloy

Abstract

Magnesium alloys development towards the 21st century

Mater. Sci. Forum

Magnesium properties-applications- potential

Mater. Sci. Eng. A

Magnesium alloys and applications

Mater. Sci. Technol.

Research for a “new age of magnesium” in the automotive industry

J. Mater. Process. Technol.

Development of the as-cast microstructure in magnesium-aluminium alloys

J. Light Met.

Mechanism of effects of rare earths on microstructure and properties at elevated temperature of AZ91 magnesium alloy

J. Rare Earths

Effects of rare earths on the microstructure, properties and fracture behavior of Mg-Al alloys

Mater. Sci. Eng. A

Microstructure and creep behaviour of Mg-12Gd-3Y-1Zn- 0.4Zr alloy

J. Rare Earths

Influence of neodymium on high cycle fatigue behavior of die cast AZ91D magnesium alloy

J. Rare Earths

Effect of Ca and Y additions on oxidation behavior of magnesium alloys at high temperatures

J. Rare Earths

Ignition-proof mechanism of magnesium alloy added with rare earth La from first-principle study

J. Rare Earths

Effect of yttrium and cerium addition on microstructure and mechanical properties of AM50 magnesium alloy

J. Rare Earths

Mechanism of grain refinement by adding cerium in Mg and Mg alloys

Rare Metal Mater. Eng. (in Chin.)

Microstructures and mechanical properties of AZ91D alloys with Y addition

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Acta Mater.

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J. Alloys Compd.