CN102758108B - Al-Si-Mg-Sm rare earth cast aluminum alloy and preparation method thereof - Google Patents

Abstract

The invention discloses an Al-Si-Mg-Sm rare earth cast aluminum alloy and a preparation method thereof. The weight percentage of Si in the Al-Si-Mg-Sm alloy is 6.5-7.0%, and the weight percentage of Mg is 0.35% ~0.45%, the weight percentage of Sm is 0.1~0.9%, and the balance is Al. The preparation method is as follows: firstly, Al-Si-Mg alloy is added into a graphite crucible, heated in a resistance furnace until melting, and then Al-Sm master alloy is added. In the temperature range of 710~750°C, heat the above alloy melt for 20~30 minutes, then apply stirring, the stirring time is 3~5 minutes, the stirring speed is 40~50 rpm, and then keep warm for 20~30 minutes. Finally, the above alloy melt was cast and sampled when the melt temperature dropped to 700~710°C after degassing and refining. The technical effects of the invention are: the addition of rare earth Sm can effectively improve the shape and distribution of eutectic silicon, refine the spheroidized grains, increase the strengthening phase, thereby greatly improving the strength and elongation of the alloy. The rare earth cast aluminum alloy in the present invention has simple preparation method, low cost, easy control of addition amount, and no three wastes pollution.

Description

A kind of Al-Si-Mg-Sm rare earth casting aluminum alloy and its preparation method

technical field

The invention relates to an aluminum alloy preparation method, in particular to an Al-Si-Mg-Sm rare earth cast aluminum alloy and a preparation method thereof.

Background technique

As a typical lightweight material in metal materials, aluminum alloy has excellent characteristics such as high strength, low density, high fracture toughness, and high stress corrosion resistance, and is widely used in the fields of machinery, chemical industry, automobile, construction, aviation, and aerospace . For aluminum alloy ingots, refining grains can make the internal structure uniform, reduce segregation, improve plasticity and tensile strength, and prevent defects such as cracks and shrinkage cavities.

ZL101 alloy mechanical strength (GB/T1173-1995): cast state σ _b =155MPa, δ=2%; T6 state: σ _b =225MPa, δ=1%

Obviously, the mechanical properties of ZL101 aluminum alloy are low, and there are deficiencies, which cannot meet the requirements of high bearing capacity. At the same time, limited to the characteristics of material composition and technical process, there are also deficiencies, such as various impurities and coarse needle-like eutectics in the structure. Silicon and iron-containing compounds, coarse aluminum matrix and other problems affect the improvement of the mechanical properties of cast products, so it is necessary to alloy ZL101 aluminum alloy with rare earth.

Rare earth elements have unique electronic layer structure and physical and chemical properties, unique 4f electronic structure, large atomic magnetic moment, and strong spin coupling characteristics, and their influence on aluminum alloys is also quite unique. The modification of rare earth elements has the characteristics of long-term effect and remelting stability, which is better than other modification agents, and has better deoxidation and desulfurization capabilities.

Research on rare earth aluminum alloys is increasing at home and abroad, but the effect of rare earth Sm as an alloying element on the structure and properties of Al-Si-Mg cast aluminum alloys has not been reported, so it has great research value.

Contents of the invention

The object of the present invention is to provide an Al-Si-Mg-Sm rare earth cast aluminum alloy and its preparation method. Sm is added to the Al-Si-Mg alloy in an appropriate amount, which can effectively improve the morphology and distribution of eutectic silicon , to improve the mechanical properties of the alloy.

The Al-Si-Mg-Sm rare earth cast aluminum alloy provided by the present invention is characterized in that: 0.1-0.9% by weight of Sm is added to the Al-Si-Mg alloy, and the Al- The weight percentage of Si in the Si-Mg alloy is 6.3-6.5%, the weight percentage of Mg is 0.7-0.8%, and the balance is Al.

The present invention is realized in this way, and the preparation method is: adding Al-Si-Mg alloy into a graphite crucible, heating it in a resistance furnace until melting, and then adding an Al-Sm master alloy, wherein the rare earth element Sm accounts for 10% of the total weight of the alloy. 0.1~0.9%. In the temperature range of 710~750°C, heat the above alloy melt for 20~30 minutes, then apply stirring, the stirring time is 3~5 minutes, the stirring speed is 40~50 rpm, and then keep warm for 20~30 minutes. Finally, the above alloy melt was cast and sampled when the melt temperature dropped to 700-710°C after degassing and refining.

The technical effect of the present invention is: the addition of rare earth Sm in the aluminum alloy will not increase the production cost, and the addition of rare earth Sm can obviously promote the refinement and spheroidization of the primary phase α-Al, so that the bulk and acicular eutectic silicon becomes It is fine and fibrous, and makes the distribution on the grain boundary change from agglomeration to uniform dispersion, thereby greatly improving the strength and elongation of the alloy. The rare earth cast aluminum alloy in the invention has simple preparation method, low cost, easy control of addition amount, and no three wastes pollution.

Description of drawings

Fig. 1 is the microfibrous structure of Al-6.4Si-0.75Mg alloy;

Figure 2 is the microfibrous structure of Al-6.4Si-0.75Mg-0.9Sm alloy.

Detailed ways

The present invention will be further illustrated by following implementation examples.

Implementation Example 1: First, add Al-6.4Si-0.75Mg (mass fraction) alloy into a graphite crucible, melt the alloy in a resistance furnace at a melting temperature of 750°C, and keep it warm for 20 minutes after the metal is completely melted, and then pass it into High-purity nitrogen (99.999% pure) degassing and refining. After standing still, cast it into a metal mold to obtain an Al-Si-Mg alloy ingot, and the casting temperature is 710°C.

Implementation Example 2: First, add Al-6.3Si-0.7Mg (mass fraction) alloy into a graphite crucible, heat it in a resistance furnace until it melts, then add Al-15%Sm master alloy, in which the rare earth element Sm accounts for the total weight of the alloy 0.3%. At 750° C., the above alloy melt was kept warm for 20 minutes and then stirred. The stirring time was 3 minutes and the stirring speed was 40 rpm, and then kept warm for 20 minutes. Finally, the above alloy melt was cast and sampled when the melt temperature dropped to 700°C after degassing and refining.

Implementation Example 3: First, add Al-6.5Si-0.8Mg (mass fraction) alloy into a graphite crucible, heat it in a resistance furnace until it melts, then add Al-15%Sm master alloy, in which the rare earth element Sm accounts for the total weight of the alloy 0.6%. At 730° C., the above alloy melt was kept warm for 25 minutes and then stirred. The stirring time was 5 minutes at a stirring speed of 50 rpm, and then kept warm for 25 minutes. Finally, the above alloy melt was cast and sampled when the melt temperature dropped to 710°C after degassing and refining.

Implementation Example 4: First, add Al-6.4Si-0.75Mg (mass fraction) alloy into a graphite crucible, heat it in a resistance furnace until it melts, then add Al-15%Sm master alloy, in which the rare earth element Sm accounts for the total weight of the alloy 0.9%. At 740° C., the above alloy melt was kept warm for 30 minutes and then stirred. The stirring time was 5 minutes and the stirring speed was 50 rpm, and then kept warm for 30 minutes. Finally, the above alloy melt was cast and sampled when the melt temperature dropped to 700°C after degassing and refining.

The ingots obtained in the above four implementation examples are processed into tensile samples according to the GB/T228-2002 metal material room temperature tensile test method, and the mechanical properties of different implementation examples are tested on the tensile testing machine, as shown in Table 1 Show.

It can be seen from Table 1 that as the Sm content increases, the mechanical properties of the as-cast alloy increase significantly. When the Sm content increases to 0.9%, the tensile strength of the alloy reaches 232.91 MPa, compared with that without adding Sm, the alloy matrix It has increased by 34%, and the elongation reaches 4.6%, which is 142.1% higher than that of the alloy matrix without Sm.

The ingots obtained in Example 1 and Example 4 are sampled, and the microstructure of the alloy is observed under an optical microscope after grinding, polishing, and corrosion, as shown in Figure 1 (Example 1) and Example 2 (Example 4) shown. It can be seen from the figure that the addition of rare earth Sm can significantly promote the refinement and spheroidization of the primary phase α-Al, making the eutectic silicon change from block and needle shape to fine fiber shape, and making eutectic silicon in the crystal The boundary aggregation becomes evenly dispersed, thereby greatly improving the strength of the alloy. Moreover, the process is simple, safe and reliable, easy to operate, and free from three waste pollution.

Table 1. Mechanical properties of Al-Si-Mg alloys before and after adding Sm under as-cast conditions

Claims (2)

1. A kind of Al-Si-Mg-Sm rare earth casting aluminum alloy, it is characterized in that: in Al-Si-Mg alloy, added the Sm that rare earth casting aluminum alloy weight percentage is 0.1～0.9%, described Al-Si - The weight percentage of Si in the Mg alloy is 6.3-6.5%, the weight percentage of Mg is 0.7-0.8%, and the balance is Al. 2. a kind of preparation method of a kind of Al-Si-Mg-Sm rare earth casting aluminum alloy described in claim 1 is characterized in that: Al-Si-Mg alloy is joined in the graphite crucible, is heated in resistance furnace to After melting, add Al-Sm master alloy, in which the rare earth element Sm accounts for 0.1~0.9% of the total weight of the alloy. In the temperature range of 710~750°C, keep the above alloy melt for 20~30 minutes and then apply stirring. The stirring time is 3~5 minutes, the stirring speed is 40~50 rpm, and then keep warm for 20~30 minutes. Finally, the above alloy melt is cast and sampled when the melt temperature drops to 700~710°C after degassing and refining.