Reasons Why Titanium Alloys Are Difficult To Machine

Titanium alloy, with its unique advantages, occupies an important position in aviation, aerospace, medical and other fields, and has also risen in the field of 3C consumer electronics in the past two years, and is used in the body and structural parts of a number of hot-selling high-end smartphones.

Titanium alloy is expected to become an innovative trend in consumer electronics materials due to its lightweight, high strength and good texture, which can help improve the design of smartphones and significantly reduce the weight of the body. However, the difficult-to-machine properties of titanium alloys have always bothered engineers and technicians.

 the Titanium alloy processing difficulties shown as belllow:

1. Temperature concentration

Most titanium alloys have a very low thermal conductivity, only 1/7 of steel, 1/16 of aluminum, and 1/25 of copper. As a result, the heat generated during the cutting process is not easily dissipated and is concentrated in the cutting area. Tip temperatures can rise to 1000°C, leading to rapid tool wear, cracking, and chip build-up, shortening tool life.

The cutting high temperature is concentrated on the tip of the tool, which makes it difficult to dissipate heat and the tool is fragile. The high temperature also destroys the surface integrity of titanium alloy parts, reduces the geometric accuracy of the parts, and causes work hardening, which seriously reduces their fatigue strength.

2. Strong affinity

Titanium alloys have good affinity and tend to form long and continuous chips during turning and drilling. These chips can wrap around the tool and hinder its function. When the cutting depth is too large, it is easy to cause the knife to stick, burn or break.

The affinity advantage is valuable in many areas, such as in ion pumps where titanium is used as the cathode plate. When titanium atoms are sputtered onto the inner wall of the anode tube, they are able to adsorb gas molecules, creating an ultra-high vacuum environment.

3. Elastic deformation

The elastic modulus of titanium alloys is relatively low. For example, the elastic modulus of TC4 is only 110Gpa, while that of 45 steel is 210Gpa. The elastic modulus of stainless steel such as 303, 304, and 316 is also around 200Gpa. When processing titanium alloys, elastic deformation is prone to occur, especially when processing thin-walled or ring-shaped parts. When thin-walled parts are processed, local deformation exceeds the elastic range and plastic deformation occurs, and the strength and hardness of the material at the cutting point increase significantly.

Cutting pressure causes the workpiece to elastically deform and rebound, increasing the friction between the tool and the workpiece, generating additional heat, and exacerbating the problem of poor thermal conductivity of titanium alloys.

4. Vibration

The elasticity of titanium alloys may be beneficial in part performance, but it becomes a major cause of vibration during the cutting process. The vibration generated by machining titanium alloy is 10 times that of steel. Since the cutting heat is concentrated in the cutting part, zigzag chips will be generated, resulting in fluctuations in cutting power.