Abstract
In the present work, Mg-4Al-xNd (x = 0, 1, 4 wt.%) alloys were prepared by a stir casting method, and the effect of the addition of Neodymium (Nd) as-cast and of heat-treated microstructures was studied. The addition of 1 wt.% Nd preferentially formed the Al2Nd phase and completely suppressed the formation of the intermetallic Mg17Al12 (γ) phase, which was initially present in the base alloy (Mg-4Al alloys). On increasing the Nd percentage from 1 to 4 wt.% in the base alloy, two intermetallic phases, Al2Nd and Al11Nd3, were observed in the microstructure, as higher levels of Nd led to a peritectic reaction between Al and the Al2Nd phase, and part of the Al2Nd transformed into the Al11Nd3 phase. The hardness of the as-cast alloy increased with the Nd content. Thus, the hardness increased from 57.1 ± 4.1 Hv of Mg-4Al to 66.5 ± 2.6 Hv of Mg-4Al-4Nd. It was also found that solutionizing and isothermal aging of alloys containing Nd at 180 °C for 96 h led to the size reduction of Al- and Nd-containing intermetallics without altering their morphologies. Further, it was found that Nd does not have any effect on the aging kinetics of the alloys because all of the alloys with and without Nd attained peak hardness at 24 h of aging time.
Highlights
Magnesium alloys possess an attractive combination of properties such as outstanding specific strength and stiffness, high damping capacity, excellent dimensional stability, and recyclability [1]
In order to circumvent the deleterious effect of the γ phase, several alloying elements such as Ca, Sr and rare earth elements that are preferentially reactive to Al over Mg have been added to Mg-Al alloys [7,8,9]
The addition of 1 wt.% Nd to alloy resulted in the complete suppression of the γ phase, peaks of α-Mg andofAlα-Mg
Summary
Magnesium alloys possess an attractive combination of properties such as outstanding specific strength and stiffness, high damping capacity, excellent dimensional stability, and recyclability [1]. The most widely used magnesium alloys are based on the Mg-Al system, where Al is added to improve strength and castability. The use of Mg-Al alloys is restricted to non-critical parts due to their poor hardness and creep properties at temperatures beyond 120 ◦ C [3,4,5]. This is attributed to the discontinuous grain boundary precipitation of a low melting point γ phase from the supersaturated solid solution of α-Mg along with the coarsening of γ in the interdendritic eutectic region at elevated temperatures [6]. In order to circumvent the deleterious effect of the γ phase, several alloying elements such as Ca, Sr and rare earth elements that are preferentially reactive to Al over Mg have been added to Mg-Al alloys [7,8,9]
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