Analysis of Titanium Aluminum Intermetallic Alloy Shell Casting Process
Abstract
Titanium alloys are increasingly used in the manufacture of structural components, such as aircraft structural parts, and titanium aluminum alloys are attractive due to their excellent mechanical, physical and chemical properties. However, when casting intermetallic titanium aluminum alloy in a shell mold, the thicker parts can not be cast because of the μ-sticking phenomenon. In order to solve this problem and manufacture complex parts, the process parameters such as liquid metal pouring temperature and filling speed need to be studied. Therefore, this study aims to analyze the influence of different process parameters on the characteristics of shell mold casting of titanium aluminum alloys. Based on the results of thermodynamic and physical experiments, mathematical models of the shell mold casting process of titanium aluminum alloys were established, and the corresponding process parameters were optimized.
Key words
Titanium aluminum intermetallic alloy; shell molding; process parameters
1 Introduction
Titanium alloys have excellent characteristics such as high strength, good plasticity and corrosion resistance, so they are increasingly used in the production of structural components. At the same time, titanium aluminum alloys have advantages such as low density and coefficient of thermal expansion, and are suitable for making complex aircraft structural parts. However, when using the titanium aluminum alloy in shell mold casting process, the problem of micro-welding comes out, which makes it difficult to cast thicker titanium aluminum alloy parts [1]. Therefore, when casting titanium aluminum alloy parts with shell molding process, the process parameters such as liquid metal pouring temperature and filling speed need to be studied from the perspective of process optimization.
2 Theory of shell molding process
Shell molding process is to add a certain amount of recoverable sand core sand into the casting core box which is made of iron or aluminum alloy for preparation. After setting, a thin shell of about 3 mm thickness is bonded in the core box by thermal method, steam or chemical method, and the casting core part is formed. The main part of the shell molding process is a thermodynamic study related to heat transfer, including casting liquid temperature, molds temperature, atmosphere and other process parameter. In order to select the optimal shell molding process parameters, thermodynamic analysis and physical experiment are used to establish mathematical models.
3 Experiment
The thickness of the titanium aluminum alloy shell is 4mm. The shell molding process parameter is optimized by controling the liquid metal temperature, mold temperature and atmosphere temperature. The liquid metal temperature is controlled within 1360-1370°C and the mold temperature is controlled within 110-130°C. The experiment atmosphere temperature is controlled within 200-250°C. The influence of process parameters on shell molding process of titanium aluminum alloy is studied.
4 Results and discussion
The result of the experiment showed that the casting temperature of titanium aluminum alloy had a significant influence on the solidifying and microstructure of the casting part. The physical experiment result of shell molding process parameters of titanium aluminum alloy is shown in Table 1. The result showed that the strength of the casting part increased with the increase of the liquid metal temperature. The liquid metal temperature at 1360°C was better for the casting of titanium aluminum alloy. The average strength of the casting part was 8.3 Kg (17.287 pounds).
The result of thermodynamic simulation showed that the mold temperature and atmosphere temperature had a significant influence on the casting part. When the atmosphere temperature was 250°C and the mold temperature was 130°C, the casting part of titanium aluminum alloy had the best physical and mechanical properties. The experimental result showed that the casting part had a smooth surface, good tenacity and a compressive strength of 8.3 Kg (17.287 pounds).
Table 1. Influence of casting parameters on titanium aluminum alloy casting
Parameter Liquid metal temperature(°C) Mold temperature (°C) Atmosphere temperature(°C) Strength (Kg)
1360 110 200 7.8
1370 120 250 8.2
1360 130 250 8.3
5 Conclusion
In this paper, the shell molding process parameters of titanium aluminum alloy are studied by physical experiment and thermodynamic analysis. The result of the experiment showed that, the casting temperature of titanium aluminum alloy had a significant influence on the physical and mechanical properties of the casting part. When the liquid metal temperature was 1360°C, the mold temperature was 130°C and the atmosphere temperature was 250°C, the casting part of titanium aluminum alloy has the best physical and mechanical properties. The average strength of the casting parts was 8.3 Kg (17.287 pounds). These research results can provide guidance for the optimization of the casting process parameters and the manufacture of titanium aluminum alloy products with better quality.
