C15–Al₂Ca Precipitation in a Mg–Al–Ca Alloy

Abstract

The coarsening kinetics of a fine C15Al 2 Ca Laves phase with a plate-like morphology precipitated within the primary ¡-Mg grains were investigated for Mg5Al1.5Ca alloy aged at 523 K. The Al 2 Ca precipitate coarsened as its coherence was retained in the aging time below 300 h, and a quantitative relationship was obtained between precipitate length (l) and aging time (t) as l £ t 0.23 . However, the ¡/C15 coherent interface changed into a semi-coherent interface by introduction of misfit dislocations on the planar surface of the precipitates in the aging time above 300 h, which resulted in the promotion of Al 2 Ca coarsening. The Al 2 Ca phase was assumed to precipitate through a nucleation and growth mechanism rather than spinodal decomposition, and its coarsening was explained using the terrace-ledge-kink mechanism. The result shows that the aspect ratio of the Al 2 Ca precipitates was predominantly determined by the aging temperature, and it decreased at higher aging temperatures.

Creep of a Die-Cast Mg–5Al–2Ca Alloy: An Overview

“…2. 43) The C15 precipitates are most clearly observable at the incident beam direction of B ¼ ½11 20 and the reciprocal lattice vector of g = 0002. [44][45][46] Numerous C15 precipitates, measuring approximately 20 nm in length, are uniformly distributed along the (0001) basal plane of the primary ¡-Mg grains.…”

HRTEM Characterization of an Age-Hardened Mg–Ca Binary Alloy

“…5,6) The morphology and coarsening kinetics of the Al 2 Ca phase, which precipitates within the primary ¡-Mg phase of a MgAlCa alloy during aging treatment, have been extensively investigated. 7) Coherent Al 2 Ca precipitates exhibit a hexagonal plate-like morphology, with a planar surface parallel to the (0001) ¡ basal plane. Moreover, the sides of the hexagonal plate are parallel to the {11-20} ¡ second columnar plane of the ¡ matrix.…”

Interface Strengthening of α-Mg/C14–Mg2Ca Eutectic Alloy

“…Another approach for enhancing the high-temperature strength by utilizing intermetallic phases is to control the microstructure so that the intermetallic phase and matrix are layered via eutectic/eutectoid reactions [13][14][15][16]. A Mg-Al-Ca ternary system, which typically exhibits excellent non-flammability, is a promising alloy system for developing cost-effective heat-resistant magnesium alloys [17][18][19][20][21][22]. When Mg-Al-Ca ternary alloys are melted and cast in the Mg-rich composition region, three kinds of eutectic reactions can take place during solidification: first, L → α-Mg + A12-Mg 17 Al 12 ; second, L → α-Mg + C36-(Mg,Al) 2 Ca; and third, L → α-Mg + C14-Mg 2 Ca [23].…”