Grain refinement of AZ91D magnesium alloy by SiC

Microstructural evolution and phase transformations during partial remelting of AZ91D magnesium alloy refined by SiC

“…The details about grain refinement and preparation of cast alloy rods can be found in reference [12]. The rods (Ф 16 mm) refined by 0.2 wt.% SiC particles and having fine equiaxed grains with size of 71 m were cut into small specimens (Ф 16 mm × 10 mm).…”

“…Among these approaches, carbon inoculation has significant refining effect and good adaptability for the aluminum bearing alloys with different compositions and impurity contents, and thus is a promising way for commercial use if the introduction of carbon can be well resolved [10,11]. The authors investigated the grain refinement of AZ91D alloy by SiC particles and a technique with good maneuverability and reliability has been developed [12]. The grain size can be decreased from 311 m of the not refined alloy to 71 m of the refined alloy by 0.2 wt.% SiC particles.…”

Effect of Initial Grain Size on Microstructure and Mechanical Properties of Extruded Mg-9Al-0.6Zn Alloy

“…The~0.17 wt pct SiC added to the molten AZ91 in the present study therefore produced a fine structure. Although the primary a-Mg phase in Mg-Al alloys cannot heterogeneously nucleate on the surface of SiC particles, [20,21] the heterogeneous nucleation of a-Mg can occur during solidification on the surface of Al 4 C 3 [19,22] or Al 2 MgC 2 [23] formed by a reaction between SiC particles and Al in the molten alloy, resulting in a decrease in the grain size. Furthermore, any Si decomposed from the SiC particles can react with Mg to eventually form a Mg 2 Si phase with ''Chinese-script'' morphology, [22] though the volume fraction of these phases significantly decreases with decreasing SiC addition.…”

“…Although the primary a-Mg phase in Mg-Al alloys cannot heterogeneously nucleate on the surface of SiC particles, [20,21] the heterogeneous nucleation of a-Mg can occur during solidification on the surface of Al 4 C 3 [19,22] or Al 2 MgC 2 [23] formed by a reaction between SiC particles and Al in the molten alloy, resulting in a decrease in the grain size. Furthermore, any Si decomposed from the SiC particles can react with Mg to eventually form a Mg 2 Si phase with ''Chinese-script'' morphology, [22] though the volume fraction of these phases significantly decreases with decreasing SiC addition. Consequently, although Mg-3Al-10SiC [23] and AZ91-5SiC [22] (wt pct) alloys typically contain a relatively large amount of Mg 2 Si and/or remaining SiC particles, second phases such as Al 4 C 3 , Al 2 MgC 2 , or Mg 2 Si are in such low concentration in Mg-3Al-0.3SiC [23] and AZ91-0.2SiC [22] (wt pct) alloys as to be below the critical threshold value required for XRD analysis.…”

“…Furthermore, any Si decomposed from the SiC particles can react with Mg to eventually form a Mg 2 Si phase with ''Chinese-script'' morphology, [22] though the volume fraction of these phases significantly decreases with decreasing SiC addition. Consequently, although Mg-3Al-10SiC [23] and AZ91-5SiC [22] (wt pct) alloys typically contain a relatively large amount of Mg 2 Si and/or remaining SiC particles, second phases such as Al 4 C 3 , Al 2 MgC 2 , or Mg 2 Si are in such low concentration in Mg-3Al-0.3SiC [23] and AZ91-0.2SiC [22] (wt pct) alloys as to be below the critical threshold value required for XRD analysis. Likewise, in the present study, no second phases other than a small quantity of Al 8 Mn 5 could be observed due to the very small amount of SiC added (~0.17 wt pct).…”