Effect of Ca on the microstructure and tensile properties of Mg–Zn–Si alloys at ambient and elevated temperature

Influence of heat treatment and aging on microstructure and mechanical properties of Mg‐1.8Zn‐0.7Si‐0.4Ca alloy

“…The formation of Ca 2 Mg 6 Zn 3 as a principle precipitate in Mg-Zn-Ca systems has been reported by previous researchers. For example, it was reported that Mg 2 Ca and Ca 2 Mg 6 Zn 3 phases are formed during the solidification of the MgÀCa with low content of zinc (under 1 %) at 503 8C and at 399 8C, respectively [23]. By increasing the amount of zinc in MgÀCa system (more than 1 %), Mg 2 Ca phase diminishes and the eutectic phase of Mg+ Ca 2 Mg 6 Zn 3 is formed by the following equation: [19,24] L !…”

“…One of the most recent and important applications of magnesium alloys is in medical industry as biodegradable materials since they can be absorbed in human body [3]. Although certain titanium alloys or stainless steel are widely used as the permenant and non-permanent bone implants, but nowadays the magnesium based alloys are the more appropriate candidates for the non-permanent application, because; (i) they are biodegradable, hence, no need for secondary surgery for their removal, (ii) their elastic moduli (45 GPa) are closer to that of the natural bone (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25), (iii) magnesium is an essential element for the human body, and (iv) they have a low density being close to that of human bone [4,5]. However, the high corrosion rate, low mechanical properties, and low cold formability are the magnesium main setbacks [6,7].…”

Effect of Ca addition on modification of primary Mg2Si, hardness and wear behavior in Mg–Si hypereutectic alloys

“…Furthermore, some of Ca atoms could adsorb in the Mg 2 Si crystal plane as shown in Fig. 6a and d. It would reduce the surface energy of the Mg 2 Si crystals by lattice distortion due to the existence of Ca in the Mg 2 Si lattice, because the atomic radius of Ca with 2.23 Â 10 À10 m, is much larger than that of Mg or Si with 1.72 Â 10 À10 m, 1.46 Â 10 À10 m, respectively [23]. This results in the preferred growth habit and growth rate of the Mg 2 Si phase being suppressed.…”

“…4d and e. Under the equilibrium solidification conditions, CaMgSi particles can be crystallized from the molten alloy as the temperature decreases, and then the primary Mg 2 Si is solidified [23]. Therefore, the formation of the CaMgSi particles resulted in the decrease in the volume fraction of the primary Mg 2 Si, because a portion of the available Si is consumed previously.…”

“…Surface active elements such as Sr, Ca, P, Ba and Bi have been added to Sicontaining Mg alloys to modify the morphology of Mg 2 Si [21e28]. Among them, Ca could modify and refine both the primary and eutectic Mg 2 Si in Mge6Zne4Si alloy [23] as well as eutectic Mg 2 Si in Mge6Zne1Si [24] and Mge5Ale1Zne1Si alloy [25]. However, up to now, the modification effect of Ca on microstructure and wear behavior of hypereutectic MgeSi alloys has not been reported.…”