Abstract
Fluidity tests of pure aluminum 1070 and Al-Si alloys with Si contents of up to 25% were conducted using a die cast machine equipped with a spiral die. The effects of the channel gap, die temperature, and injection speed on the fluidity were investigated. When the channel gap was small (0.5 mm), the flow length of the 1070 was minimized, and the fluidity increased monotonically at a gradual rate with increasing Si content. In contrast, larger gaps yielded convex fluidity–Si content curves. Additionally, heating the die had less of an influence on the fluidity of the 1070 than on that of the Al-Si alloy. These results are discussed in the context of the peeling of the solidification layer from the die based on the thicknesses of foils and strips cast by melt spinning and roll casting, respectively. At lower Si contents, heat shrinkage was greater and the latent heat was lower. When the heat shrinkage was greater, the solidification layer began to peel earlier, and the heat transfer between the solidification layer and the die became smaller. As a result, the fluidity of the 1070 was greatest when the channel gap was 0.8 mm.
Highlights
Aluminum alloys with excellent fluidity are considered suitable for a range of applications, including thin-walled products such as lightweight heat sinks with thin fins
The increase in the fluidity with the plunger speed was greater at lower Si contents for Si contents below 6%
When the Si content was greater than 6%, the increase in the fluidity with the plunger speed was the same regardless of the Si content
Summary
Aluminum alloys with excellent fluidity are considered suitable for a range of applications, including thin-walled products such as lightweight heat sinks with thin fins. The effect of the Si content on the fluidity of Al-Si alloys, including pure Al, has been discussed from the perspective of solidification patterns, such as columnar and equiaxed dendrites. The excellent fluidity of pure aluminum initially decreases with the addition of a small amount of alloying elements because of the expanded crystallization range and the change in solidification pattern from planar to mushy. The fluidity increases with further increases in the alloying content until a maximum is reached at the eutectic composition, where the solidification pattern is planar [1,2,3,4,5]. The fluidity of Al-Si alloys has been discussed with particular attention paid to the solidification mechanism
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