Microstructure and compressive properties of chill-cast Mg–Al–Ca alloys

Abstract

Mg 82 Al 8 Ca 10 was determined to be a pseudo-binary eutectic composition [liquid solidifying into ␣-Mg and (Mg,Al) 2 Ca in the Mg-Al-Ca ternary system with a eutectic melting temperature of 789 K]. A series of Mg x (Al 0.44 Ca 0.56 ) 100−x alloys, where 75 ഛ x ഛ 95, were cast into ⌽4 mm rods using copper mold casting. The eutectic alloy exhibits the highest fracture strength, f ‫ס‬ 609 MPa. For 75 ഛ x ഛ 79, the alloys have hypereutectic microstructures with Mg 2 Ca as the primary phase, and f is reduced together with diminishing plasticity. For hypoeutectic alloys with 86 ഛ x ഛ 95, the volume fraction of the primary ␣-Mg dendrites dispersed in the eutectic matrix increases with increasing x, resulting in a gradual decrease of the yield and fracture strengths but improved plastic strain to as large as 9%. The refined microstructures created in bulk samples via chill casting can lead to a good combination of strength and plasticity, with specific strength superior to commercial Mg alloys.

Mg-Al-Ca In-Situ Composites with a Refined Eutectic Structure and Their Compressive Properties

“…An appropriate adjustment of the alloy composition can lead to a unique composite microstructure containing ductile dendrites and hard particles dispersed in the strong eutectic matrix. This is different from the microstructures developed in previous studies, [11][12][13][14] where a single reinforcement phase was dispersed in the strong matrix. Such composites provide an increased strength without adversely affecting the plasticity.…”

“…The ductile dendrites separate and restrict the propagation of the highly localized shear bands in small interdendritic regions and contribute significantly to the plasticity and work hardening behavior. Adopting this cost-effective route for the Mg alloys, in-situ composites composed of ductile Mg dendrites [13] or 14-H type long-period stacking Mg phase [14] embedded in the ultrafine eutectic matrix have been developed to improve the combination of strength and ductility.…”

Effect of additional Zn on plasticity of large-scale Mg-based nanostructure-dendrite composites

“…In contrast, the SEM fractography presented in Fig. 4(b) indicates a high homogeneous dimple morphology density typical of ductile fracture [23,26,27]. Moreover, the SEM micrograph obtained at a higher magnification indicates that the size of the dimples on the fracture surface are more or less identical to those of the dendrites (i.e.…”

“…With the goal of improving high-strength alloy plasticity, nanostructure-dendrite composites have been developed using Ti- [13][14][15][16][17], Zr- [18,19], Fe- [20][21][22], and Mg- [23][24][25] based alloys. The Mg-Al-Ca nanostructure-dendrite composites have every high strength (~300 MPa) and significantly enhanced plasticity (≈6 %) [23]. Mg-Cu-Zn-Y nanostructure-dendrite composite also exhibits strengths of 330 MPa with plasticity of 12 %, which is comparable to Mg-based BMGs and BMG composites [25].…”

Evolution of Constitution, Structure, and Morphology in FeCo-Based Multicomponent Alloys

“…[4] Recently, dendriteeutectic (D-E) composites were developed in Ti-, Fe-, Cu-, Mg-, and Al-based chill-cast multicomponent hypoeutectic alloys as a competitive replacement of BMGs. [5][6][7][8][9][10][11][12] Compared to the BMGs with close chemical compositions, this kind of D-E composite shows similar strength and remarkable plasticity as well as a more controllable production process. Normally, the microstructure of the hypoeutectic alloys is characteristic of soft dendrite (a terminal solid solution phase of basis element) embedded into hard eutectics (a networklike framework phase).…”