Microstructure Evolution And Mechanical Properties Of Electron Beam Additive Repaired TC4 Titanium Alloy

TC4 titanium alloy is widely used in the aerospace field with its excellent comprehensive mechanical properties.However,the parts’ damage caused by the harsh working environment and the components needs to be replaced in time.The short-term and high cost of service has hindered the development of the aviation industry in a certain extent.Due to the tip damage of engine twisted blade,this paper using thin-walled plate to simulate the repair process by electron beam additive manufacturing method.In this paper,the electron beam additive manufacturing method is used to repair the thin-walled parts of TC4 titanium alloy and made them continue to use.This paper explores the tests to learn samples organizational evolution and mechanical behaviors in two ways.One is to simulate the temperature field of the deposition process,the other is to set 8 group experiments including one-way/reciprocating forming path,single/double-channel additive mode,and TC4/TC4 EH welding wire.It is found through computer simulation that the temperature field of the same track is distributed in a stepwise manner,and the inter-layer interval affects the uniformity of temperature distribution.During the inter-layer interval,the cooling rate changes from fast to slow,and the higher the number of layers,the slower the cooling rate.The macroscopic morphology of TC4 titanium alloy thin-walled parts behaved as coarse raw β-column grains.Samples sections’ macroscopic morphology could be divided into four parts.They are the HAZ(heat affected zone)in base metal,the “layers” zone,the uniform zone without “layer” and the equiaxed grains zone of the surface.The microstructure is composed of fine acicular martensites and grew thin and long from the base metal.The microhardness of specimen with one-way forming path,single-channel additive mode and using TC4 EH welding wire was highest in all samples;specimen using TC4 EH welding wire have higher tensile strength,up to 94% of the base metal and elongation reaches 90% or more of the substrate in tensile test;specimen using TC4 EH welding wire also have much better impact toughness in impact test.The tensile and impact fracture morphology indicated that the fracture of the specimen was plastic fracture.