Magnesium-contained high-silicon aluminum alloys structural materials and manufacture method thereof

Abstract

The magnesium-contained high-silicon aluminum alloys for use as structural materials, including profiles, bars, sheets, and forgings, are manufactured by a process including the steps of: casting an alloy ingot by direct chill casting, preheating the ingot to disperse eutectic Si phase particles, and thermal-plastic processing and heat-treating to obtain the product with a final shape and a modified microstructure. The aluminum alloys contain 0.2˜2.0 wt % of Mg and 8˜18 wt % of Si, and have homogeneous and fine microstructure, wherein the aluminum matrix is equiaxed with an average grain size less than 6 μm, and the silicon and second phase particles are dispersed with an average size less than 5 μm. Without adding any modifiers, they are low-costly produced by incorporating the direct chill casting with thermal-plastic processing and heat treatment, which give rise to good plasticity and relatively high strength.

Description

BACKGROUND OF THE PRESENT INVENTION[0001]1. Field of Invention[0002]The present invention relates to aluminum alloys and their method of preparation, and more particularly to magnesium-contained high-silicon aluminum alloys for use as structural materials, and the manufacture method thereof.[0003]2. Description of Related Arts[0004]Aluminum-silicon alloys (Al—Si alloys), especially those with high silicon content, are widely used in car and aviation industries, due to their low density, high wear resistance, high anti-corrosiveness, and low thermal expansion coefficient. With the common solidification method for preparation of Al—Si alloys, there usually appear large silicon particles and eutectic plates, resulting in a dramatically increased brittleness of the alloys. Thus, it is difficult to improve the solidified microstructure and to obtain various shaped high-performance structural materials through subsequent plastic deformation, which poses a bottleneck for more general appli...

AI Technical Summary

Benefits of technology

[0006]An object of the present invention is to provide high-silicon aluminum alloys (Al—Si alloys) that contain magnesium (Mg) and have good plasticity and high strength for use as structural materials, and the manufacture method thereof. Without adding any modifiers, the Al—Si alloys are manufactured at low cost with the direct chill casting followed by the thermoplastic process and heat treatment.

[0021]The present invention overcomes the cognition prejudice traditionally imposed on Al—Si alloys. Without adding any modifiers, an unexpected effect has been reached on the magnesium-contained high-silicon aluminum alloys prepared by incorporating conventional direct chill casting method with thermal-plastic process and heat treatment. They are typically of fine-dispersed silicon particles and second phase at equiaxed Al matrix, associated with a relatively high strength and good plasticity for potential use as structural materials

[0024]As the most common aluminum extrusion alloys, the 6063 alloys have been widely used in architectures, vehicles, and decorations etc., which have great need in the existing market. Once the 6063 alloys are partially replaced by the magnesium-contained high-silicon aluminum alloys of the present invention, it will bring great economic benefits. In addition, the use of an increased amount of Si in the alloys can dramatically conserve the aluminum resource.

Problems solved by technology

With the common solidification method for preparation of Al—Si alloys, there usually appear large silicon particles and eutectic plates, resulting in a dramatically increased brittleness of the alloys.

Thus, it is difficult to improve the solidified microstructure and to obtain various shaped high-performance structural materials through subsequent plastic deformation, which poses a bottleneck for more general applications of these alloys.

However, the rapid solidification method can only allow preparation of tiny ingots with a diameter less than 10 mm.

As for the powder metallurgy method, it enables to obtain a relatively large-sized part, but suffers from a complicated process with high fabrication cost.

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