[China Aluminum Network] aluminum-titanium alloy profiles due to its small density, high specific strength, high temperature resistance, oxidation resistance and other characteristics, widely used. However, the poor machinability of aluminum-titanium alloy profiles has affected the widespread use of this material.
Aluminum-titanium alloy profiles are alloy elements added to industrial pure titanium to increase the strength of titanium. Titanium alloys can be divided into three types: a titanium alloy, b titanium alloy and a+b titanium alloy. Ab The titanium alloy is composed of a and b phases. This type of alloy has stable microstructure, high temperature deformation, toughness, and good plasticity. It can be quenched and aged to strengthen the alloy. The performance characteristics of titanium alloys are mainly manifested in:
1) High specific strength. Aluminum-titanium alloy profiles have a low density (4.4kg/dm3), but their specific strength is greater than that of ultra-high-strength steels.
2) High thermal strength. The thermal stability of aluminum-titanium alloy profiles is good, and its strength is about 10 times higher than that of aluminum alloys at 300-500°C.
3) Great chemical activity. Titanium can produce strong chemical reactions with oxygen, nitrogen, carbon monoxide, and water vapor in the air, forming TiC and TiN hardened layers on the surface.
Poor thermal conductivity. The thermal conductivity of titanium alloy is poor, the thermal conductivity of titanium alloy TC4 at 200°C is l=16.8W/m·°C, and the thermal conductivity is 0.036 cal/cm·sec·°C.
Analysis of machining characteristics of aluminum-titanium alloy profiles First, the thermal conductivity of titanium alloys is low, which is only 1/4 of steel, 1/13 of aluminum, and 1/25 of copper. Due to slow heat dissipation in the cutting zone, it is not conducive to heat balance. During the cutting process, the heat dissipation and cooling effects are very poor, and it is easy to form high temperatures in the cutting zone. After the processing, the parts deform and rebound greatly, resulting in increased cutting tool torque and rapid wear of the cutting edge. Reduced durability. Secondly, the low thermal conductivity of the titanium alloy makes it difficult for the heat of cutting to dissipate in the small area around the cutting tool. The rake face has increased friction, it is not easy to remove chips, cutting heat is not easily dissipated, and tool wear is accelerated. Later, titanium alloys have high chemical activity and can easily react with tool materials at high temperatures to form solubilising and diffusion, causing sticking, burning, and cutting.
Tool material selection should meet the following requirements:
• Adequate hardness. The hardness of the tool must be much larger than that of aluminum-titanium alloy.
• Adequate strength and toughness. Because the cutters take great torque and cutting forces when cutting aluminum-titanium alloys, they must have sufficient strength and toughness.
• Adequate wear resistance. Due to the toughness of the titanium alloy, the cutting edge must be sharp during machining, so the tool material must have sufficient wear resistance so as to reduce the work hardening. This is an important parameter for selecting a titanium alloy tool.
• Tool material and titanium alloy have poor affinity. Due to the high chemical activity of aluminum-titanium alloys, it is necessary to prevent the tool materials and aluminum-titanium alloys from forming a solution or diffusion alloy, resulting in sticking and burning.
After tests on common domestic tool materials and foreign tool materials, it is shown that the use of high-cobalt tools is effective, and the main role of cobalt can enhance the secondary hardening effect, improve the red hardness and hardness after heat treatment, while having high toughness, wear resistance Sex, good heat dissipation, more suitable for processing aluminum and titanium alloy profiles.
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