CN107236875B - A kind of phosphorus titanium dual metamorphism method of cocrystallized Al-Si alloy - Google Patents

Abstract

The invention relates to the field of nonferrous metal preparation, in particular to a method for double modification of phosphorus and titanium for eutectic aluminum-silicon alloy. In the present invention, the eutectic aluminum-silicon alloy is heated, melted, degassed and refined, and the eutectic aluminum-silicon alloy is modified by using Al-3P master alloy and Al-5Ti master alloy successively to obtain the deteriorated eutectic aluminum-silicon alloy. The microstructure and macroscopic mechanical properties have been improved. The processing method of the present invention is simple, low in cost, applicable to large-scale industrial production, and has broad application prospects.

Description

Phosphorus-titanium double modification method of eutectic aluminum-silicon alloy

technical field

The invention relates to the field of nonferrous metal preparation, in particular to a method for double modification of phosphorus and titanium for eutectic aluminum-silicon alloys.

Background technique

Eutectic aluminum-silicon alloy has good casting properties, especially high specific strength, small thermal expansion coefficient, good wear resistance and corrosion resistance, and is widely used in the automotive industry, especially cylinder blocks, cylinder heads, pistons and valve lifters. In the eutectic aluminum-silicon alloy manufactured by the traditional process, the eutectic silicon is distributed in the α-Al matrix in the form of coarse needles, which severely splits the matrix and significantly reduces the mechanical properties and machinability of the alloy. Technological workers and industries often use modification treatment to improve the shape and size of eutectic silicon to meet the performance requirements of eutectic aluminum-silicon alloy.

Scholars at home and abroad have conducted a lot of research on various modifiers and found that the elements that modify eutectic silicon include Na, Sr, Sb, Te, Ti, B and rare earth elements La, Ce, Y, etc. The modification mechanism of Na is similar to that of Sr, and both rely on adsorption on the growth steps of eutectic silicon to hinder its growth into sheets to achieve the effect of refining the eutectic structure. The modification of Sb makes the eutectic silicon structure branch in the form of flakes to achieve the effect of refinement. The addition of Te does not change the growth mode of eutectic silicon fundamentally, but makes eutectic silicon thinner and longer, hinders the lateral growth of eutectic silicon and accelerates vertical growth. Al ₃ Ti is small in size and dispersedly distributed. It crystallizes earlier than Al solid solution, has the same lattice type and similar lattice constant as Al, and can be used as the crystallization core of Al solid solution to refine the grains of Al solid solution. Although AlB ₂ cannot be used as the core of α-Al, it provides a nucleation substrate for the precipitation of Si. There is a precipitated Si phase in the liquid phase. As the temperature decreases, α-Al may nucleate on crystalline Si. , to achieve the purpose of refinement. Rare earth contains many elements, and the metamorphic mechanism is relatively complicated. The theory of interfering atomic groups believes that the addition of rare earth weakens the bonding between Si-Si and Si-Al atomic groups and strengthens the bonding of Al-Al atomic groups, leading to the nucleation of α-Al first and the supercooling of the Si phase. When eutectic crystallization, α -Al, as the leading phase, precipitates and grows first, thus limiting the growth of eutectic silicon. There is a view that the main effect of rare earth metamorphism is due to the enrichment of rare earth elements La, Ce, etc. at the solidification interface, which leads to the supercooling of the composition of the crystal front, so that the growth of silicon crystals is easy to branch, and primary silicon and eutectic silicon can be formed. refinement. There is also a view that Ce can capture oxygen in alloy liquid or Al ₂ O ₃ to form dispersed CeO ₂ . CeO ₂ is similar to Si in crystal structure and lattice constant, and can be used as the core of silicon heterogeneous nucleation. P is generally used as a primary crystal Si refiner. Al reacts with P to form AlP compound, which is dispersed in the alloy melt. Its crystal structure is the same as that of Si, which belongs to the face-centered cubic lattice, and the lattice constant is similar. The modification mechanism: AlP serves as the heterogeneous nucleation core of primary Si, thereby refining the primary Si. Adding Al-P master alloy to the eutectic aluminum-silicon alloy can introduce a large amount of primary crystal Si, thereby shifting the eutectic point to the left and refining the eutectic Si.

Existing researches use the addition of modifiers to refine the α-Al phase or eutectic Si phase in hypoeutectic or eutectic Al-Si alloys, and improve the mechanical properties of the alloy by improving its microstructure. There is no mention of introducing primary α-Al phase and primary Si phase into the eutectic Al-Si alloy to regulate its microstructure so as to improve the mechanical properties of the eutectic Al-Si alloy.

Contents of the invention

The technical problem to be solved by the present invention is: in order to solve the problem of low strength and ductility of the current eutectic aluminum-silicon alloy, the present invention provides a double modification method of phosphorus and titanium for the eutectic aluminum-silicon alloy.

The technical solution adopted by the present invention to solve the technical problem is: a double modification method of phosphorus and titanium for eutectic aluminum-silicon alloy, and its specific operation steps include:

(1) Melting Al-12.6wt.% Si eutectic aluminum-silicon alloy in a crucible with an electric furnace, heating the eutectic aluminum-silicon alloy melt to 700-780°C;

(2) adding hexachloroethane for degassing and refining;

(3) Press the Al-3P master alloy into the melt quickly, stir it evenly and then keep it warm; wherein, the mass fraction of phosphorus in the Al-3P master alloy is 3%, and Al-3P transforms the eutectic aluminum-silicon structure into primary crystal silicon tissue.

(4) Move the melt to an electric furnace at 650-750°C;

(5) Press the Al-5Ti master alloy into the melt, stir it evenly and keep it warm; wherein, the mass fraction of titanium in the Al-5Ti master alloy is 5%, and the Al-5Ti transforms the eutectic aluminum-silicon structure into primary α- Al organization.

(6) pouring the melt into a preheated metal mold to obtain a double-modified eutectic aluminum-silicon alloy of phosphorus and titanium.

Preferably, the electric furnace described in step (1) and step (4) is a well-type electric furnace; the crucible described in step (1) is a graphite crucible.

Preferably, the Al-3P master alloy added in step (3) is 0.1% to 1.0% of the mass of the eutectic aluminum-silicon alloy, and the Al-5Ti master alloy added in step (5) is eutectic aluminum-silicon 0.1-0.4% of the alloy mass.

As preferably, the holding time in step (3) is 5-10min; the holding time in step (5) is 3-7min.

Preferably, the metal mold preheating temperature in step (6) is 150°C.

Further, as a preference, the addition amount of the Al-3P master alloy described in the step (3) is 0.4% of the mass of the eutectic aluminum-silicon alloy, and the addition amount of the Al-5Ti master alloy described in the step (5) is the eutectic aluminum-silicon alloy. 0.2% of the alloy mass. Under such parameter conditions, the primary Si is the most, the average size is small, the eutectic Si is the finest, and the area fraction of primary α-Al increases to 45%. At this time, the properties of the eutectic Al-Si alloy most.

The beneficial effects of the present invention are: the present invention uses Al-3P master alloy and Al-5Ti master alloy to carry out double modification to eutectic Al-Si, and its microscopic microstructure and macroscopic mechanical properties have all been improved: ① Observation of eutectic The microstructure of aluminum-silicon alloy found that the present invention introduces a large amount of primary Si and primary α-Al into the eutectic aluminum-silicon alloy, and refines the primary Si, so that the original eutectic aluminum-silicon structure is transformed into primary α-Al , the mixed structure of primary crystal Si and eutectic aluminum-silicon structure, the morphology of the alloy changes, from acicular to granular; ② detection of the mechanical properties of the eutectic aluminum-silicon alloy found that the eutectic aluminum-silicon alloy prepared by the present invention The strength and plastic toughness are greatly improved, and the comprehensive mechanical properties are improved obviously. The processing method of the present invention is simple, low in cost, applicable to large-scale industrial production, and has broad application prospects.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

FIG. 1 is a photo of the microstructure of the eutectic aluminum-silicon alloy prepared in Example 1.

FIG. 2 is a photo of the microstructure of the eutectic aluminum-silicon alloy prepared in Example 2.

Fig. 3 is a photo of the microstructure of the eutectic aluminum-silicon alloy prepared in Example 3.

Figure 4 is a photo of the microstructure of the unmodified eutectic Al-Si alloy.

FIG. 5 is a photo of the microstructure of the eutectic aluminum-silicon alloy prepared in Example 4.

Fig. 6 is a photo of the microstructure of the eutectic aluminum-silicon alloy prepared in Example 5.

FIG. 7 is a photo of the microstructure of the eutectic aluminum-silicon alloy prepared in Example 6. FIG.

Fig. 8 is a photo of the microstructure of the eutectic aluminum-silicon alloy prepared in Example 7.

Detailed ways

The present invention will be described in more detail through examples, but the protection scope of the present invention is not limited to these examples.

Example 1

Double modification of eutectic Al-Si alloy by Al-3P and Al-5Ti:

(1) Melting 10kg of Al-12.6wt.% Si eutectic aluminum-silicon alloy in a graphite crucible using a well-type electric furnace, and heating the eutectic aluminum-silicon alloy melt to 740-750°C;

(2) adding hexachloroethane for degassing and refining;

(3) Rapidly press 40g of Al-3P master alloy into the melt, stir evenly and keep warm for 8min;

(4) Move the melt to an electric furnace at 700°C;

(5) Press the Al-5Ti master alloy of 10g into the melt, stir it evenly and keep it warm for 5min;

(6) The melt is poured into a metal mold preheated at 150° C. to form a cake-shaped eutectic aluminum-silicon alloy with a diameter of 10 mm.

Example 2

Double modification of eutectic Al-Si alloy by Al-3P and Al-5Ti:

(1) Melting 10kg of Al-12.6wt.% Si eutectic aluminum-silicon alloy in a graphite crucible using a well-type electric furnace, and heating the eutectic aluminum-silicon alloy melt to 740-750°C;

(2) adding hexachloroethane for degassing and refining;

(3) Rapidly press 40g of Al-3P master alloy into the melt, stir evenly and keep warm for 8min;

(4) Move the melt to an electric furnace at 700°C;

(5) 20g of Al-5Ti master alloy is pressed into the melt, stirred evenly and kept warm for 5min;

(6) The melt is poured into a metal mold preheated at 150° C. to form a cake-shaped eutectic aluminum-silicon alloy with a diameter of 10 mm.

Example 3

Double modification of eutectic Al-Si alloy by Al-3P and Al-5Ti:

(1) Melting 10kg of Al-12.6wt.% Si eutectic aluminum-silicon alloy in a graphite crucible using a well-type electric furnace, and heating the eutectic aluminum-silicon alloy melt to 740-750°C;

(2) adding hexachloroethane for degassing and refining;

(3) Rapidly press 40g of Al-3P master alloy into the melt, stir evenly and keep warm for 8min;

(4) Move the melt to an electric furnace at 700°C;

(5) 40g of Al-5Ti master alloy is pressed into the melt, stirred evenly and kept warm for 5min;

(6) The melt is poured into a metal mold preheated at 150° C. to form a cake-shaped eutectic aluminum-silicon alloy with a diameter of 10 mm.

Example 4

Double modification of eutectic Al-Si alloy by Al-3P and Al-5Ti:

(1) Melting 10kg of Al-12.6wt.% Si eutectic aluminum-silicon alloy in a graphite crucible using a well-type electric furnace, and heating the eutectic aluminum-silicon alloy melt to 740-750°C;

(2) adding hexachloroethane for degassing and refining;

(3) 10g of Al-3P master alloy is quickly pressed into the melt, stirred evenly and then kept for 8 minutes;

(4) Move the melt to an electric furnace at 700°C;

(5) 20g of Al-5Ti master alloy is pressed into the melt, stirred evenly and kept warm for 5min;

(6) The melt is poured into a metal mold preheated at 150° C. to form a cake-shaped eutectic aluminum-silicon alloy with a diameter of 10 mm.

Example 5

Double modification of eutectic Al-Si alloy by Al-3P and Al-5Ti:

(1) Melting 10kg of Al-12.6wt.% Si eutectic aluminum-silicon alloy in a graphite crucible using a well-type electric furnace, and heating the eutectic aluminum-silicon alloy melt to 740-750°C;

(2) adding hexachloroethane for degassing and refining;

(3) Rapidly press 20g of Al-3P master alloy into the melt, stir evenly and keep warm for 8min;

(4) Move the melt to an electric furnace at 700°C;

(5) 20g of Al-5Ti master alloy is pressed into the melt, stirred evenly and kept warm for 5min;

(6) The melt is poured into a metal mold preheated at 150° C. to form a cake-shaped eutectic aluminum-silicon alloy with a diameter of 10 mm.

Example 6

Double modification of eutectic Al-Si alloy by Al-3P and Al-5Ti:

(1) Melting 10kg of Al-12.6wt.% Si eutectic aluminum-silicon alloy in a graphite crucible using a well-type electric furnace, and heating the eutectic aluminum-silicon alloy melt to 740-750°C;

(2) adding hexachloroethane for degassing and refining;

(3) Rapidly press 70g of Al-3P master alloy into the melt, stir evenly and keep warm for 8min;

(4) Move the melt to an electric furnace at 700°C;

(5) 20g of Al-5Ti master alloy is pressed into the melt, stirred evenly and kept warm for 5min;

(6) The melt is poured into a metal mold preheated at 150° C. to form a cake-shaped eutectic aluminum-silicon alloy with a diameter of 10 mm.

Example 7

Double modification of eutectic Al-Si alloy by Al-3P and Al-5Ti:

(1) Melting 10kg of Al-12.6wt.% Si eutectic aluminum-silicon alloy in a graphite crucible using a well-type electric furnace, and heating the eutectic aluminum-silicon alloy melt to 740-750°C;

(2) adding hexachloroethane for degassing and refining;

(3) Rapidly press 100g of Al-3P master alloy into the melt, stir evenly and keep warm for 8min;

(4) Move the melt to an electric furnace at 700°C;

(5) 20g of Al-5Ti master alloy is pressed into the melt, stirred evenly and kept warm for 5min;

(6) The melt is poured into a metal mold preheated at 150° C. to form a cake-shaped eutectic aluminum-silicon alloy with a diameter of 10 mm.

Comparative example 1

On the basis of Example 2, Al-3P is used to modify the eutectic aluminum-silicon alloy separately:

(1) Melting 10kg of Al-12.6wt.% Si eutectic aluminum-silicon alloy in a graphite crucible using a well-type electric furnace, and heating the eutectic aluminum-silicon alloy melt to 740-750°C;

(2) adding hexachloroethane for degassing and refining;

(3) Rapidly press 40g of Al-3P master alloy into the melt, stir evenly and keep warm for 8min;

(4) Move the melt to an electric furnace at 700°C;

(5) The melt is poured into a metal mold preheated at 150° C. to form a cake-shaped eutectic aluminum-silicon alloy with a diameter of 10 mm.

Comparative example 2

On the basis of Example 2, the eutectic aluminum-silicon alloy is modified separately by using Al-5Ti:

(1) Melting 10kg of Al-12.6wt.% Si eutectic aluminum-silicon alloy in a graphite crucible using a well-type electric furnace, and heating the eutectic aluminum-silicon alloy melt to 740-750°C;

(2) adding hexachloroethane for degassing and refining;

(3) Move the melt to an electric furnace at 700°C;

(4) Press the Al-5Ti master alloy of 20g into the melt, stir and keep warm for 5min;

(5) The melt is poured into a metal mold preheated at 150° C. to form a cake-shaped eutectic aluminum-silicon alloy with a diameter of 10 mm.

Performance Testing:

1. Observing the microstructure of eutectic Al-Si alloy:

1. After pre-grinding and polishing the cake-shaped eutectic aluminum-silicon alloy prepared in Examples 1-3, observe its microstructure with an optical microscope, and the results are shown in Figures 1-3. When the amount of Al-5Ti added in Example 1 is 0.1wt.%, the microstructure of the eutectic Al-Si alloy is shown in Figure 1. At this time, the number of primary Si is large, the eutectic Si is coarse, and the area of primary α-Al The fraction is 35%; when the Al-5Ti addition of embodiment 2 is 0.2wt.%, the microstructure of the eutectic aluminum-silicon alloy is shown in Figure 2, and the number of primary crystal Si is the largest at this moment, and the average size is smaller, The eutectic Si is the finest, and the area fraction of primary α-Al increases to 45%. When the addition of Al-5Ti in Example 3 is 0.4wt.%, the microstructure of the eutectic Al-Si alloy is shown in Figure 3. At this time, the number of primary crystal Si is large, the eutectic Si is relatively coarse, the area fraction of primary α-Al is 40%, and the α-Al dendrites are relatively coarse. The above phenomena indicate that the eutectic Al-Si microstructure prepared in Example 2 is at the optimum level.

2. After pre-grinding and polishing the unmodified eutectic aluminum-silicon alloy and the cake-shaped eutectic aluminum-silicon alloy prepared in Examples 4-7, observe its microstructure with an optical microscope, and the results are shown in Figures 4-8. There is a large amount of acicular eutectic silicon in the unmodified eutectic aluminum-silicon alloy, and the microstructure of the eutectic aluminum-silicon alloy is shown in Figure 4; when the addition of Al-3P in Example 4 is 0.1wt.%. The microstructure of the crystalline aluminum-silicon alloy is shown in Figure 5, a small amount of primary Si appears in the structure, and the eutectic silicon has no obvious change; when the addition of Al-3P in Example 5 is 0.2wt.%, the eutectic aluminum-silicon The microstructure of the alloy is shown in Figure 6, the number of primary crystal Si increases, and the eutectic silicon is refined; when the addition of Al-3P in Example 2 is 0.4wt.%, the microstructure of the eutectic Al-Si alloy As shown in Figure 2, the number of primary crystal Si is the largest at this time, and the average size is smaller, and the eutectic Si is the thinnest; when the addition of Al-3P in Example 6 is 0.7wt.%, the microstructure of the eutectic Al-Si alloy As shown in Figure 7, the number of primary crystal Si is significantly reduced, and most of the eutectic silicon is transformed from acicular to granular; when the amount of Al-3P added in Example 7 is 1.0wt.%, the eutectic Al-Si alloy is significantly The microstructure is shown in Figure 8, the primary Si basically disappears, and the eutectic Si is uniformly distributed in granular form. The above phenomena indicate that the eutectic Al-Si microstructure prepared in Example 2 is at the optimum level.

2. Testing the mechanical properties of eutectic aluminum-silicon alloy:

Use WDW-300 microcomputer-controlled electronic universal testing machine to test the tensile properties of alloy samples according to GB/T 228-2002 (tensile properties include tensile strength and elongation, the higher the elongation, the better the plasticity and toughness), the tensile The speed is 2mm/min; use the HBE-3000A electronic Brinell hardness tester to test the Brinell hardness of the alloy sample according to GB/T231.1-2002. The tensile test and hardness test results of the alloy are shown in Table 1. The data show that: ① Al-5Ti plays a decisive role in improving the elongation of the alloy. Generally, within a certain range, increasing the amount of Al-5Ti added, The elongation of the alloy is also increased; Al-3P plays a decisive role in improving the tensile strength and hardness of the alloy. Generally, within a certain range, increasing the addition of Al-3P will increase the tensile strength and hardness of the alloy. Increase accordingly; ② After adding 0.4wt.% Al-3P and 0.2wt.% Al-5Ti to the eutectic aluminum-silicon alloy in Example 2, the tensile strength, hardness and elongation of the alloy are all the highest. The comprehensive mechanical properties of the crystalline Al-Si alloy are the best, and compared with the unmodified eutectic Al-Si alloy, the comprehensive mechanical properties are significantly improved.

Table 1 Mechanical properties of eutectic Al-Si alloy

Inspired by the above-mentioned ideal embodiment according to the present invention, through the above-mentioned description content, relevant workers can make various changes and modifications within the scope of not departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, but must be determined according to the scope of the claims.

Claims (3)

1. a double modification method of phosphorus and titanium of eutectic aluminum-silicon alloy, it is characterized in that, the specific operation steps of described modification method comprise: (1) Melting Al-12.6wt.% Si eutectic aluminum-silicon alloy in a crucible with an electric furnace, heating the eutectic aluminum-silicon alloy melt to 700-780°C; (2) adding hexachloroethane for degassing and refining; (3) Press the Al-3P master alloy into the melt quickly, stir it evenly and keep it warm; the addition of the Al-3P master alloy is 0.4% of the eutectic aluminum-silicon alloy quality; (4) Move the melt to an electric furnace at 650-750°C; (5) Pressing the Al-5Ti master alloy into the melt, stirring evenly and keeping it warm; the addition of the Al-5Ti master alloy is 0.2% of the eutectic aluminum-silicon alloy quality; (6) pouring the melt into a preheated metal mold to obtain a double-modified eutectic aluminum-silicon alloy of phosphorus and titanium. 2. The phosphorus-titanium double modification method of eutectic aluminum-silicon alloy as claimed in claim 1, characterized in that, the holding time in step (3) is 5-10min; the holding time in step (5) is 3-7min. 3. The phosphorus-titanium dual modification method of the eutectic aluminum-silicon alloy according to claim 1, characterized in that the preheating temperature of the metal mold in step (6) is 150°C.