Study On The Joining Process Between Mg Alloy And Amorphous Polyethylene Terephthalate (PET)

With the emergence of new materials and new structure, integrated application of metal materials and non-metallic composites develop a lot, and it has been widely used in the field of national defense and national production. Because of the unique light weight, high strength and other mechanical and physical properties, magnesium light alloys and plastics reflect the huge advantage in aerospace, automobile body manufacturing, and electronic field. In recent years, more and more researchers turn to study the connection between plastics and magnesium light alloy. Since it is critical to get a better connection and excellent properties of lightweight composite materials, looking for the right connection method is of great importance. Based on the magnesium alloy and plastics, this paper starts from the new method and new thought of material preparation, chooses different experimental methods, and does a further research by focusing on the connectivity of the magnesium alloy and plastics.In this paper, we use pulsed YAG laser of500W to do pulse lap welding tests between AZ31B magnesium alloy and polyethylene terephthalate (PET). In the case of certain clamping force of clamping, it realizes a good connection between magnesium alloy and PET by adjusting the welding speed, the laser current, pulsed width, frequency, defocusing amount and other test parameters. Meanwhile, this paper analyzes the influence of welding speed on the welding joint surface morphology, and the results show that when welding speed is too high, welding line, solder skips, uneven weld and other flaws are easy to appear; when the welding speed is too low, flaws such as weld penetration is seen. Also, the paper does the joint shear load test of tensile samples by using mechanical properties tester, and then summarizes influence law of the defocusing amount, laser current, and pulsed width on the joint tensile load. Finally, the paper analyzes the typical morphology of joint by using scanning electron microscopy (SEM), and determines compositions of welding joint by using infrared spectrum and electron probe. Through the experiment data in the process of laser welding of magnesium alloy with PET, magnesium oxide film and the carbon monoxide perssad of PET probably have conducted the complexation reaction, and have formed chemical bonds which mixes matrix together, thus have formed a relative strong joint tensile shear load.Using the continuous laser, magnesium alloy and PET are connected successfully. Through the analysis of mechanical tensile test data, we find that the welding joint strength is higher than that by using pulsed laser connection, and the highest tensile shear reached491N that is the67.8%of PET base material, which has the certain actual application value. By tensile test, the influence law of the power density, welding speed, and defocusing amount on the tensile shear load increases first, then reaches the maximum, finally decreases. By the analysis of typical joints of the cross section morphology, it can be referred that the right size and number of discrete bubbles form helps to form high tensile shear load of the joint. Through the EDS spectrum analysis data, the results shows that magnesium alloy surface is oxidated at high temperature, and the oxide film forms in the surface layer; at the same time, we conduct infrared spectrum analysis of the joint carbon element.TIG welding successfully realizes the connection between the magnesium alloy AZ31B and PET. Through a series of tests, the tensile test gets the highest tensile shear of359N, and the TIG joint tensile shear load is generally lower than that is done by the pulsed laser welding. Also, the paper summarizes the base value current, welding speed, and the influence law of tungsten electrode on the tensile shear load.