Modification of near-eutectic Al–Si alloys with rare earth element samarium

Abstract

The modification of near-eutectic Al-Si alloy with samarium additions (0-0.9 wt.% content) has been studied. The thermal analysis results indicated that the addition of Sm in Al-12Si alloy caused a depression of eutectic temperature (ΔT E ). And it was found that Sm was capable of breaking down the primary a-A1 phases, giving rise to an increment in the number of dendrites. Simultaneous primary Si refinement and eutectic modification were achieved by Sm addition. When 0.6 wt.% Sm was added to the alloy, the silicon in Al-12Si alloy was best refined and showed a fully modified, fine fibrous eutectic structure; the primary a-Al phase appears as a slightly dual dendritic-cellular nature and a pine-tree structure. Moreover, the mechanical properties were investigated by the tensile test. A good combination of ultimate tensile strength (217 MPa) and elongation (1.3%) was obtained when the addition of Sm was up to 0.6 wt.%.

Effect of Solidification Rate and Rare Earth Metal Addition on the Microstructural Characteristics and Porosity Formation in A356 Alloy

“…Figures 9(a)-9(f) show examples of the eutectic Si morphology in A356 alloy samples treated with different amounts of RE, without (a, c, d) and with (b, e, f) Sr addition. It should be mentioned here that, according to the atomic radius ratio, La / Si is 1.604 and Ce / Si is 1.559, which theoretically confirms the abovementioned observation [23].…”

“…As eutectic temperature is easy to measure, it is generally employed to assess whether or not a melt is properly modified. However, if temperature alone is used as the criterion for proper modification, it is difficult to detect overmodified structures, because the greatest change of temperature occurs in the unmodified-to-modified transition [23]. Figure 7(a) exhibits the depression in the eutectic temperature with the addition of La in the absence of Sr.…”

Microstructure and Mechanical Properties of Al–12.6Si Eutectic Alloy Modified with Al–5Ti Master Alloy

“…Such properties are attractive to the automobile industry, particularly for engine blocks, pistons cylinder heads, chain cover, and valve lifters. [11,12] Alloying with Ti, [13] B, [14][15][16] Sr, [8,17] rare earth elements such as Sc, [18] La, [19,20] Ce, [2] Nd, [21] Sm, [22] Eu, [23,24] Er, [25] and Yb [26,27] has shown to effectively improve both microstructure and tensile properties of eutectic Al-Si alloys. [7][8][9][10] Besides fast cooling rate and vibration, the typical method of refining the eutectic Al-Si alloy microstructure is the addition of certain modifying elements.…”

“…[7][8][9][10] Besides fast cooling rate and vibration, the typical method of refining the eutectic Al-Si alloy microstructure is the addition of certain modifying elements. [11,12] Alloying with Ti, [13] B, [14][15][16] Sr, [8,17] rare earth elements such as Sc, [18] La, [19,20] Ce, [2] Nd, [21] Sm, [22] Eu, [23,24] Er, [25] and Yb [26,27] has shown to effectively improve both microstructure and tensile properties of eutectic Al-Si alloys.…”

“…[15,28] This led to the improvement of the morphology of eutectic Si, while reducing the size of eutectic Si via Sr or rare earth alloys through modification. [17,22,23,27,29,30] After complex modification by Ti, B, Sr, and rare earth elements, [19,[31][32][33][34] the morphology of eutectic Si has been improved, and the size of primary a-Al and eutectic silicon in Al-Si alloys could be refined. Dong et al [35] thought that the coupled twinning can eliminate anisotropy of eutectic silicon growth on the whole, which leads to the eutectic silicon changes from flake into fiber.…”