As its small density, high specific strength, high temperature resistance and good oxidation resistance, aluminum and titanium alloy profiles are widely used in many field. But the mechanical properties of Al Ti alloy profiles are poor, which affects the wide use of this material.
Alloy elements are added into pure titanium to improve the strength of titanium. Titanium alloy can be divided into three kinds: a titanium alloy, B titanium alloy and a+b titanium alloy. AB titanium alloy is composed of a and B dual phase. These alloys are stable in structure, good in deformation, toughness and plasticity. They can be hardened and aged, so that the alloy can be strengthened. The performance characteristics of titanium alloys are mainly manifested in:
1. High specific strength.
Aluminum titanium alloy profiles are small in density (4.4kg/dm3) and light in weight, but their specific strength is greater than that of ultra high strength steel.
2. High heat intensity.
The thermal stability of aluminum alloy profiles, at 300 to 500 DEG C, 10 times higher than the strength of Aluminum Alloy.
3. Large chemical activity.
Titanium can react with oxygen, nitrogen, carbon monoxide, water vapor and other substances in the air to form a hardened layer of TiC and TiN on the surface.
Analysis of machining characteristics of aluminum titanium alloy profiles
First of all, titanium alloy with low thermal conductivity is only 1/4 of steel, 1/13 of aluminum and 1/25 of copper. Because the cutting zone heat slowly, is not conducive to the heat balance during the machining process, the heat and the cooling effect is poor, easy to form a high temperature in the cutting zone after machining parts springback deformation, resulting in increased torque, cutting tool edge wear, durability decreased. Secondly, the thermal conductivity of titanium alloy is low, which makes the cutting heat accumulate in the small area around the cutting knife, it is difficult to distribute, the friction of the front face is increased, the chip is not easily removed, the cutting heat is not easy to diffuse, and the tool wear is accelerated. Finally, the chemical activity of titanium alloy is high, it is easy to react with the cutting tool material at high temperature and form the deposition, diffusion, resulting in sticking, burning, cutting and so on.
The selection of tool materials shall meet the following requirements:
1. enough hardness. The hardness of the tool must be far greater than the hardness of aluminum and titanium alloy.
2. sufficient strength and toughness. Because the cutting tool takes on great torque and cutting force when cutting aluminum and titanium alloy, it must have enough strength and toughness.
3. sufficient wear resistance. Because of the good toughness of the titanium alloy, the cutting edge should be sharp, so the tool material must have enough wear resistance, so as to reduce the work hardening. This is an important parameter for selecting titanium alloy cutting tools.
4., the tool material and titanium alloy affinity is poor. Because of the high chemical activity of aluminum titanium alloy, it is necessary to avoid the formation of alloying and diffusion of tool material and aluminium titanium alloy, resulting in sticking and burning.
After a test of commonly used tool materials and cutting tool materials abroad show that the ideal high cobalt tool effect, main function of cobalt can enhance two hardening effect, improve the red hardness and hardness after heat treatment, with toughness, wear resistance, good heat dissipation is higher, more suitable for the processing of aluminum alloy profiles.
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