Titanium and titanium alloys are widely used in aerospace and other fields due to their excellent comprehensive properties such as low density, high specific strength, corrosion resistance, high temperature resistance, non-magnetic properties and good welding performance. However, some of the physical and mechanical properties of titanium alloys have brought many difficulties to the cutting process. Titanium alloy has small deformation coefficient, high tool tip stress, high cutting temperature, high chemical activity, prominent bond wear and diffusion wear, high elastic recovery and high chemical affinity during cutting. Therefore, it is easy to produce stick in the cutting process. Knife, peeling, bite, etc., the tool temperature rises rapidly, causing the tool to wear or even completely destroy. Because titanium alloy has the advantages of high specific strength, good corrosion resistance and high temperature resistance, titanium alloy has been rapidly developed in the aerospace field since the 1950s. Titanium alloy is one of the main structural materials of modern aircraft and engines, which can reduce the weight of the aircraft and improve the structural efficiency. The proportion of titanium in aircraft materials is 7% for passenger aircraft Boeing 777, 10.3% for transport aircraft C-74, and 8% for fighter aircraft F-4. However, due to the high price of titanium alloy and poor wear resistance, it limits its use. In recent decades, great progress has been made in titanium alloys and other researches for aerospace applications at home and abroad, and many alloys have also been widely used. This paper discusses the titanium alloy milling technology in aerospace products for the reference of peers. 1. Introduction to titanium alloy Titanium is an isomer of isotopes with a melting point of 1 720 ° C. It is a close-packed hexagonal lattice structure below 882 ° C and is called α titanium. It is a body-centered cubic character structure above 882 ° C and is called β titanium. Using the different characteristics of the above two structures of titanium, adding appropriate alloying elements, gradually changing the phase transition temperature and phase content to obtain titanium alloys of different microstructures. At room temperature, titanium alloys have three kinds of matrix structures, and titanium alloys are classified into the following three categories: (1) α-titanium alloy It is a single-phase alloy composed of α phase solid solution. It is α phase at normal temperature or at a higher practical application temperature. It is structurally stable and has higher wear resistance than pure titanium. Strong oxidizing power. At 500 to 600 ° C, the strength and creep resistance are maintained, but the heat treatment is not strengthened, and the room temperature strength is not high. (2) β-titanium alloy It is a single-phase alloy composed of β-phase solid solution. It has high strength without heat treatment. After quenching and aging, the alloy is further strengthened. The room temperature strength can reach 1 372~1 666MPa; Poor, should not be used at high temperatures. (3) α + β titanium alloy It is a dual phase alloy, has good comprehensive properties, good structural stability, good toughness, plasticity and high temperature deformation properties, can be well subjected to hot pressure processing, can be quenched and aged Strengthen the alloy. The strength after heat treatment is about 50% to 100% higher than that of the annealed state; the high temperature strength is high, and it can work for a long time at a temperature of 400 to 500 ° C, and its thermal stability is inferior to that of the α titanium alloy. The most commonly used of the three titanium alloys are α-titanium alloy and α +β-titanium alloy; α-titanium alloy has the best machinability, α + β titanium alloy is the second, and β-titanium alloy is the worst. The alpha titanium alloy is coded TA, the beta titanium alloy is coded as TB, and the alpha + beta titanium alloy is coded as TC. LED Lamp Bead light-emitting principle
The terminal voltage of the PN junction constitutes a certain potential barrier. When the forward bias voltage is applied, the potential barrier drops, and the majority carriers of the P region and the N region diffuse to each other. Since the electron mobility is much larger than the hole mobility, a large number of electrons will diffuse into the P region, which constitutes the injection of minority carriers into the P region. These electrons recombine with holes in the valence band, and the energy obtained during recombination is released in the form of light energy. This is the principle of PN junction light emission.
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1. Voltage, LED lamp beads use low-voltage Power Supply, and the power supply voltage is between 2 and 4V, which varies according to different products, so it is driven by a high-voltage power supply. Safer power supply, especially for public places.
2. Current, the working current is between 0 and 15 mA, and the brightness becomes brighter with the increase of the current.
3. Efficiency, energy consumption is reduced by 80% compared with incandescent lamps with the same luminous efficiency.
4. Applicability, very small, each unit LED chip is 3 to 5 mm square, so it can be prepared into various LED lamp bead shaped devices, and is suitable for variable environments.
5. Color, changing the current can change color. The light-emitting diode can easily adjust the energy band structure and band gap of the material through chemical modification methods to realize red, yellow, green, blue and orange multi-color luminescence. For example, an LED that is red when the current is small, can turn orange, yellow, and finally green as the current increases.