Study On The Properties Of Ti/Steel Clad Plate Prepared By Cold Spraying-Rolling Method

Ti/steel clad plates have excellent corrosion resistance and good mechanical properties.Ti/steel clad plates can save Ti resources and reduce the cost,so it has been widely used in aerospace,machinery,ships,offshore platforms,nuclear power and other fields.At present,the common methods used to fabricate Ti/steel clad plates in industry include explosion-welding,explosion-rolling,vacuum sealing welding-rolling etc.These methods have problems such as interface oxidation,insufficient interface bonding and complex process and so on.Cold spraying has the advantages of low deposition temperature,fast particle velocity and no oxidation etc.So,as a new powder solid state deposition technology,cold spraying has a remarkable application prospect in the preparation of light metals and their composites.The aim of this thesis is exploring the new technology of fabricating Ti/steel clad plate by cold spraying and hot-rolling.Pure Ti powder is deposited on a steel plate by cold spraying additive manufacture technology,and then the Ti/steel composite are combined by hot rolling to form Ti/steel clad plates.The main contents of the thesis are as follow.Firstly,the feasibility of the new technology for preparing Ti/steel clad plates by cold spraying and hot-rolling method is being explored.Using pure Ti powder and Q235 steel plates as raw materials,Ti/steel clad plate was prepared by the proposed cold spraying-rolling method.And its microstructure and mechanical properties were studied.The results show that cold spraying realized the pre-bonding of pure titanium powder and steel plate,avoiding the occurrence of interfacial oxidation.Hot-rolling repaired the pores and defects inside the Ti layer and led to metallurgical bonding of Ti/Ti interface and Ti/steel interface.After hot rolling,the Ti/steel clad plate shows a high tensile strength(590 MPa),shear strength(320 MPa).And the elongation of the Ti/steel clad plates after annealing treatment is significantly improved to 18%.The above results show that the new method of cold spraying and hot-rolling for preparing Ti/steel clad plates is feasible.The effect of annealing temperature on the microstructure and mechanical properties of Ti/steel clad plates was investigated.The rolled Ti/steel clad plates were annealed in 450?,550? and 650? respectively for 3 h.The results show that annealing promoted the recovery and recrystallization of the internal structure of Ti/steel clad plates.Annealing treatment at 450? for 3 h can completely recover the sample and eliminate the local strains.Annealing treatment at 650? for 3 h can completely recrystallize the deformed Ti layer near the interface.There are two aspects in how the annealing treatment effect the mechanical properties of the Ti/steel clad plates.On one hand,annealing eliminated the high-density dislocations inside the materials and increased the elongation.On the other hand,annealing treatment promoted the growth of the interfacial compounds including TiC and FeTi,which increased the interfacial hardness of the Ti/steel clad plate.But too big compounds grains decreased the interfacial bonding strength and elongation.The above experimental results show that 550? is the optimum annealing temperature,and the comprehensive mechanical properties of Ti/steel clad plates are better than those of other processes.Studied the influence of rolling temperature on the microstructure and mechanical properties of Ti/steel clad plates.The prefabricated Ti/steel clad plate were rolled at 850?,950? and 1050?,respectively.The results show that the rolling temperature has an important effect on the thickness and type of interfacial compounds layer.The higher the temperature,the thicker of interfacial compounds layer,the worse mechanical properties of Ti/steel clad plates.The Ti/steel clad plate rolled at 850? has a 250 nm TiC layer at the interface.It showed the best elongation(33%),and its tensile strength and shear strength is 560 MPa and 309 MPa,respectively.Ti/steel clad plate rolled at 950? has a 400 nm thick interfacial layer,which composed of a TiC zone and a mixing area of FeTi and TiC.The sample rolled at 950? shows the best tensile strength(578 MPa)and shear strength(312 MPa),while its elongation is 29%.When the rolling temperature is 1050?,Ti/steel clad plates formed a 4 ?m thick compounds layer at the interface of Ti/steel clad plates.and it has poor mechanical properties including tensile strength(516 MPa),shear strength(167 MPa)and elongation(13%).Finally,the optimized process for fabricating Ti/steel clad plates is proposed:rolling temperature is 950?,annealing condition is 550?,3 h.Ti/steel clad plates was fabricated by the optimized process,and its microstructure,mechanical properties,deformation performance and corrosion resistance were comprehensively studied.As a result,the interface of Ti/steel clad plates fabricated by the optimized process is well combined,the tensile strength,shear strength and elongation reach 599 MPa?309 MPa and 36%,respectively,and it has good deformation performance and corrosion resistance.All properties of the Ti/steel coal plates greatly exceed the national standard and Ti/steel clad plates prepared by other processes,so it has a good application prospect.