چكيده به لاتين
Nowadays forming Bimetal tubes through different types of forming processes has been interested by many researchers due to its vast applications in some industries such as aerospace, oil and petro chemistry. It is possible to combine different metals with various properties to produce these kind of tubes. The advantages of multi-layered tubes in comparison to single-layered tubes are high mechanical strength, corrosion resistance, better wear resistance and cost-effectiveness. Multi-layered tubes are produced via different methods; Due to their bonding in contact surfaces they are divided into metallurgical and mechanical methods. Severe plastic deformation (SPD) process is one of the mechanical methods that allows coating various materials and also leads to improvement in mechanical and metallurgical properties. In this study the parallel tubular channel angular pressing is considered as one of the SPD methods for coating. The tubes are pushed inside the angular channel by punch movement, and while passing through angular sections plastic deformation occurs which produces residual stress in contact surfaces and causes connection between layers. Due to the good corrosion resistance of aluminum and its high formability, aluminum is an excellent choice for coating copper. In this study, in addition to the coating of copper by aluminum, the mechanical and metallurgical properties of these tubes are also improved. Shear-bond test, hardness profile and microstructure observation in a connection area is checked for bonding quality. For instance, in coating by PTCAP method, a good adhesion between two layers has been created and the hardness and thus the strength of the tubes have been increased significantly. After performing the process at the room temperature the hardness of copper and aluminum samples increased by 125% and 87% after three passes compared to the annealed mode, respectively. Also, the grain size of the copper from 58μm in annealed sample reached 5 μm after the process.
Keywords: Bimetal tubes, severe plastic deformation processes, parallel tubular channel angular pressing, mechanical-metallurgical properties
