Relationship between Microstructure Evolution and Tensile Properties of AlSi10Mg Alloys with Varying Mg Content and Solidification Cooling Rates

Abstract

This work explored and contrasted the effect of microstructure on the tensile properties of AlSi10Mg alloys generated by transient directional solidification depending on variations in cooling rate and magnesium (Mg) content (i.e., 0.45 and 1 wt.% Mg), with a focus on understanding the dendritic growth and phases constitution. Optical and scanning electron (SEM) microscopies, CALPHAD, and thermal analysis were used to describe the microstructure, forming phases, and resulting tensile properties. The findings showed that the experimental evolution of the primary dendritic spacing is very similar when both directionally solidified (DS) Al-10 wt.% Si-0.45 wt.% Mg and Al-10 wt.% Si-1 wt.% Mg alloys samples are compared. The secondary dendritic spacing was lower for the alloy with more Mg, especially considering the range of high growth velocities. Moreover, a greater fraction of (Al + Si + Mg2Si) ternary eutectic islands surrounding the α-Al dendritic matrix was noted for the alloy with 1 wt.% Mg. As a result of primary dendritic spacings greater than 180 μm related to lower cooling rates, slightly higher tensile properties were attained for the Al-10 wt.% Si-0.45 wt.% Mg alloy. In contrast, combining dendritic refining (<150 μm) and a larger Mg2Si fraction, fast-solidified DS Al-10 wt.% Si-1 wt.% Mg samples exhibited higher tensile strength and elongation. The control of cooling rate and fineness of the dendritic array provided a new insight related to the addition of Mg in slightly higher levels than conventional ones, capable of achieving a better balance of tensile properties in AlSi10Mg alloys.

Laser Remelting of AlSi10Mg(-Ni) Alloy Surfaces: Influence of Ni Content and Cooling Rate on the Microstructure

“…When the molten alloys reached the liquidus temperatures + 5% at the thermocouple closest to the casting's bottom, water ow was activated against the external surface of the mold bottom part, promoting upward directional solidi cation. Speci c information about this experimental setup can be found in previous studies [14,15].…”

“…4. The cooling rate range varying between 14 and 0.02 o C/s may be related to changes in both microstructural morphology and length scale [14]. An α-Al matrix with a dendritic pattern (lighter areas in Figs.…”

“…Owing to that, the Laser Surface Remelting (LSR) technique can aid in the examination of preliminary data before the AM processing. Moreover, transient directional solidi cation [14,15] is another key approach for rationalizing cooling rate-microstructure dependences in Al alloys.…”

A Comparative Study on the Microstructures and Mechanical Properties of Al-10Si-0.5Mg Alloys Prepared under Different Conditions

“…Among many light alloys, the hypoeutectic Al-Si alloys are widely used as structural components. This is because Al-Si alloys exhibit low densities, low coefficients of thermal expansion, good casting properties, high strengths, high corrosion resistances, excellent wear resistances and good weldability [1][2][3]. The main alloying element, Si, increases the melt fluidity, reduces melting temperature and improves alloy properties.…”

“…For example, during traditional sand-mold casting and gravity casting processes, if the casting component itself is too large and complex, the cooling rate ( Ṫ) may vary among different locations with diverse thickness. A slower cooling rate produces coarse microstructures and lower mechanical properties, while a faster cooling rate produces finer microstructures and higher mechanical properties [3,7]. Thus, the variations in cooling rate among different locations may induce the microstructural inhomogeneity and composition segregations, which causes the non-uniformity in mechanical properties.…”