CN103469028B - Rare earth element praseodymium alloyed aluminum-silicon alloy and preparation method thereof - Google Patents

Abstract

Provided are a rare earth element praseodymium (Pr) alloyed aluminum-silicon (Al-Si) alloy and a preparation method thereof. The alloy comprises the components by the weight percentage: 9.0-12.0% of Si, 0.05-0.4% of Pr, and the balance being Al. The preparation method comprises the steps: after heating an Al-Si alloy placed in a graphite crucible to melt, adding Pr or an Al-Pr intermediate alloy at the temperature of 770-790 DEG C according to the above weight percentage, and carrying out heat preservation for 5-8 minutes; under conditions of the ultrasonic intensity of 10 W/cm<2>-38 W/cm<2>, the total ultrasonic treatment time of 3-8 minutes, each ultrasonic treatment time of 20-30 seconds, and the intermittent time of 20-30 seconds, applying intermittent ultrasonic treatment to the alloy melt, then cooling the alloy melt down to 720-740 DEG C, carrying out heat preservation for 31-180 minutes, and then carrying out coagulation forming at the cooling rate of 40-65 DEG C/min. The method can obviously promote refinement and nodularization of an alpha-Al phase; the method allows needle-shaped eutectic silicon to be changed into punctiform-shaped eutectic silicon or short rod-shaped eutectic silicon, allows the distribution of eutectic silicon to be more dispersed and more uniform, so that the method allows the microstructure and mechanical properties of the aluminum alloy to be improved significantly; and the method has simple process and convenient operation, is safe and reliable, and has no three-waste pollution.

Description

A kind of rare earth element praseodymium alloyed aluminum-silicon alloy and its preparation method

technical field

The invention belongs to the technical field of aluminum-silicon alloy and its preparation.

Background technique

Aluminum-silicon (Al-Si) alloy has excellent casting performance, no thermal cracking and looseness, and high air tightness. It has low density and good corrosion resistance, and can withstand the atmosphere. Used in seawater corrosive environments, can withstand concentrated nitric acid in industrial atmospheres. The corrosion effect of oxygen peroxide, etc.; the welding performance is also good. However, the alloy has low mechanical properties, poor heat resistance and machinability.

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. Among them, the rare earth element Pr has a significant metamorphic ability on Al-Si alloys. Huadong Jiaotong Da Zhangjian et al. studied the effect of rare earth Pr on the structure of high wear-resistant hypereutectic Al-16%Si under ordinary casting conditions, and found that rare earth Pr can be absorbed by At the front of silicon phase crystallization, the generation of large undercooling is suppressed, and it has obvious modification effect on primary silicon and eutectic silicon. Liu Ping from Shanghai Jiaotong University studied the effect of rare earth Pr on the microstructure and properties of hypereutectic Al-18%Si-Mg alloy from the perspective of the effect of rare earth Pr on the crystallization behavior of Mg ₂ Si phase in Al-18%Si-Mg alloy.

When the ultrasonic wave propagates in the Al-Si melt, it will produce positive pressure phase and negative pressure phase, which will destroy the structural integrity of the melt, reduce the continuity of acoustic resistance, and increase the micro-regional difference of the melt’s absorption of sound energy. The degree of order decreases and the crystallization core increases. Li Yinglong from Northeastern University and others studied the influence of eutectic composition (12.6% Si) and hypereutectic composition Al-20Si alloy microstructure and properties under ultrasonic action from die casting to solidification. The results show that ultrasonic has a double refinement effect on primary Si and eutectic Si, making Si broken into particles, and the mechanical strength and plasticity of the alloy are improved. Yang Jun of Hefei University of Technology studied the influence of ultrasonic power (300-1600W), ultrasonic time (20-100s), and ultrasonic temperature (600-680°C) on the microstructure and properties of hypereutectic Al-20Si alloys. Ultrasonic treatment can Significantly improve the tensile strength and elongation of A1-20% Si alloy. Liu Qingmei from Shanghai University studied the effect of side-introduced ultrasonic treatment on the solidification characteristics of eutectic Al-12.5Si alloy, and found that ultrasonic treatment during the solidification process (eutectic reaction zone 577-660°C) can significantly refine the eutectic silicon phase , to improve its morphology and distribution.

Contents of the invention

The object of the present invention is to provide a method for alloying aluminum-silicon alloy with praseodymium (Pr), which can effectively improve the morphology and distribution of primary silicon and eutectic silicon, so as to improve the mechanical properties of the alloy.

The present invention is achieved through the following technical solutions.

In the rare earth element praseodymium alloyed aluminum-silicon alloy described in the present invention, the percentage by weight of each component of the alloy is: silicon is 9.0-12.0%, praseodymium is 0.05-0.4%, and the balance is aluminum.

The invention provides a method for preparing aluminum-silicon alloy alloyed with rare earth element Pr, which is characterized in that the aluminum-silicon (Al-Si) alloy in the graphite crucible is heated to melt, and the above-mentioned weight percentage is used at a temperature of 770-790°C. Add praseodymium or aluminum-praseodymium intermediate alloy and keep warm for 5-8 minutes; after applying intermittent ultrasonic treatment to the above alloy melt, the alloy melt is cooled to 720-740°C, and after 31-180 minutes of heat preservation, it is heated at 40-65°C/min. solidified at a cooling rate.

The intermittent ultrasonic treatment of the present invention is: the ultrasonic intensity is 10w/cm ² ~38w/cm ² , the ultrasonic treatment time is 3~8 minutes in total, the ultrasonic time is 20~30 seconds each time, and the intermittent time is 20~30 seconds.

The technical effects of the present invention are: the addition of rare earth Pr under the action of intermittent ultrasound can significantly promote the refinement and spheroidization of the α-Al phase; make the acicular eutectic silicon become point-like or short-rod-like, and make its distribution more Dispersed and uniform, so that the microstructure and mechanical properties of the aluminum alloy are significantly improved. The invention has the advantages of simple process, safety and reliability, convenient operation and no pollution of three wastes.

Description of drawings

Fig. 1 is the as-cast microstructure of the alloy prepared under the conditions of Example 4.

Detailed ways

The invention will be further illustrated by the following examples.

Example 1.

Add the Al-Si alloy containing 9.0% (weight percentage) of silicon into the graphite crucible and heat until it is completely melted, add the Al-Pr master alloy at 780°C and keep it warm for 5 minutes, wherein the rare earth element Pr accounts for 0.05% of the total weight of the alloy; Then extend the ultrasonic horn into the above alloy melt for intermittent ultrasonic treatment, the ultrasonic intensity is 10w/cm ² , the total ultrasonic treatment time is 3 minutes, each ultrasonic time is 25 seconds, and the intermittent time is 25 seconds; finally the alloy After the melt was lowered to 720°C and kept for 31 minutes, it was cast in a metal mold with a cooling rate of 40°C/min.

Example 2.

Add the Al-Si alloy with silicon content of 9.8% (weight percentage) into the graphite crucible and heat until it is completely melted, add the rare earth element Pr metal at 790°C and keep it warm for 6 minutes, wherein the rare earth element Pr accounts for 0.06% of the total weight of the alloy; then Extend the ultrasonic horn into the above alloy melt for intermittent ultrasonic treatment, the ultrasonic intensity is 20w/cm ² , the total ultrasonic treatment time is 4 minutes, each ultrasonic time is 30 seconds, and the intermittent time is 20 seconds; finally the alloy is melted After the body was lowered to 720°C for 61 minutes, it was cast in a metal mold with a cooling rate of 50°C/min.

Example 3.

Add the Al-Si alloy containing 10.2% (weight percentage) of silicon into the graphite crucible and heat it until it is completely melted, add the rare earth element Pr metal at 780 ° C and keep it warm for 8 minutes, wherein the rare earth element Pr accounts for 0.12% of the total weight of the alloy; then Extend the ultrasonic horn into the above alloy melt for intermittent ultrasonic treatment, the ultrasonic intensity is 25w/cm ² , the total ultrasonic treatment time is 5 minutes, each ultrasonic time is 20 seconds, and the intermittent time is 20 seconds; finally the alloy is melted After the body was lowered to 720°C and held for 181 minutes, it was cast in a metal mold with a cooling rate of 50°C/min.

Example 4.

Add an Al-Si alloy with a silicon content of 11.4% (weight percent) into a graphite crucible and heat until completely melted, add an Al-Pr master alloy at 780°C and keep it warm for 7 minutes, wherein the rare earth element Pr accounts for 0.28% of the total weight of the alloy; Then extend the ultrasonic horn into the above alloy melt for intermittent ultrasonic treatment, the ultrasonic intensity is 30w/cm ² , the total ultrasonic treatment time is 6 minutes, each ultrasonic time is 30 seconds, and the intermittent time is 30 seconds; finally the alloy After the melt was lowered to 730°C and held for 121 minutes, it was cast in a metal mold with a cooling rate of 60°C/min.

Example 5.

Add the Al-Si alloy with silicon content of 12.0% (weight percentage) into the graphite crucible and heat until completely melted, add the Al-Pr master alloy at 770°C and keep it warm for 8 minutes, wherein the rare earth element Pr accounts for 0.4% of the total weight of the alloy; Then extend the ultrasonic horn into the above alloy melt for intermittent ultrasonic treatment, the ultrasonic intensity is 38w/cm ² , the total ultrasonic treatment time is 8 minutes, each ultrasonic time is 30 seconds, and the intermittent time is 30 seconds; finally the alloy After the melt was lowered to 730°C and held for 121 minutes, it was cast in a metal mold with a cooling rate of 65°C/min.

The ingot obtained in Example 4 was sampled, and the microstructure of the alloy was observed under an optical microscope after grinding, polishing, and corrosion, as shown in Figure 1 (Example 4). It can be seen from Figure 1 that the addition of rare earth Pr can significantly promote the refinement and spheroidization of the α-Al phase; make the blocky primary silicon with sharp corners disappear; Rod-shaped, and make the distribution more dispersed and uniform, so that the microstructure of the aluminum alloy is significantly improved. The ingot that embodiment 4 obtains is processed into circular cross-section tensile specimen according to GB/T 228-2002. It is determined that the tensile strength of the tensile sample in Example 4 is 246MPa, and the elongation is 9.4%, which is better than the tensile strength (145MPa) of ZL102 with similar alloy composition in GB/T 1173-1995 cast aluminum alloy. and elongation (4%).

Claims (1)

1. A preparation method of rare earth element praseodymium alloyed aluminum-silicon alloy, the percentage by weight of each component of the alloy is: silicon is 9.0 ~ 12.0%, praseodymium is 0.05 ~ 0.4%, and the balance is aluminum, which is characterized in that graphite After the aluminum-silicon alloy in the crucible is heated to melt, add praseodymium or aluminum-praseodymium intermediate alloy according to the above weight percentage at a temperature of 770~790°C, and keep it warm for 5~8 minutes; after applying intermittent ultrasonic treatment to the above alloy melt, the alloy melts Cool the body to 720~740°C, keep it warm for 31~180 minutes and solidify at a cooling rate of 40~65°C/min; The intermittent ultrasonic treatment is: the ultrasonic intensity is 10w/cm ² ~38w/cm ² , the ultrasonic treatment time is 3~8 minutes in total, the ultrasonic time is 20~30 seconds each time, and the intermittent time is 20~30 seconds.