Metallurgical Mechanism Analysis Of Transition Materials Matched With TA1/Q235 Heterogeneous Metals

The characteristic of dissimilar metal welding is that can give full play to the advantages of each material.Composite materials of titanium and steel are widely used in aerospace,petrochemical,marine engineering and other fields due to its low price,execllent performance and high performance price ratio.However,the application of such bimetallic plate is severely restricted because of thermo-physical properties mismathing and metallurgical incompatibility between titanium and steel.Therefore,the present work is aimed to realize the connection of titanium and steel dissimilar metals.The microstruicture evolution as well as the microstructure control have been investigated during fusion bonding of TA1 and Q235,which is of great theoretical and applied significance.In this paper,TAI and Q235 dissimilar metals were taken as research objects Composite welding materials of Cu based matched with the parent material were designed,using the multi element alloy elements such as Cu V,Ni and Ag as the metallurgical regulating elements of the transilion layer.The results of the study showed that series Cu-Ti compounds formed between Cu and Ti alloys,which inhibited the formation of brittle Fe-Ti intermetallics.In the welded joints of TA1 and Q235 dissimilar metal,the TA1 boundary presented a wider fine-grained transition zone compeared to the Q235 steel side.Moreover it was revealed that composite welding materials were prone to realize the regulate and control of the microstructure.On this basis,the Cu based composite;welding materials(Cu-V-Ni and Cu-V-Ni-Ag)were applied to weld the TA1/Q235 laminated composite material.According to the properties of the parent materials and the characteristics of welding forming technology,the corresponding welding process was preferred.It was proposed that sound joint with homogeneous microstructure distribution as well as limited Fe-Ti intermetallies was obtained when Cu-V-Ni-Ag filler material was applied.The corresponding mechanical properties of such joint were significantly improved.Based on the optimized welding process and filler materials,EBSD and TEM were applied to further identify the microstructure in typical regions of welded joint of TA1/Q235 composite plate.Cu solid solution formed between Cu-based weld metal and Fe matrix.The regions near the TA1/Q235 interface were composed of ?-Ti with FeTi intermetallics dissolved in.Cu-Ti intermetallics were formed between Cu-based weld metal and Ti weld metal.A small amount of brittle FeTi intermetallics were dissolved in the Cu solid solution.The above results determined the microstructure of TA1/Q235 butt welded joints,which provided theoretical guidance for the later mechanical performance evaluation.In order to comprehensively evaluate the overall performance of joints,the mechanical properties of TA1/Q235 welded joints were analyzed by Vivtorinox microhardness,uniaxial tensile test,three-point bending test and impact test.It was interesting to note that Cu solid solution could inhibit the initiation and propagation of cracks in weld metal.Moreover,Cu-Ti intermetallics which were relative softer showed higher resistance to cracking than Fe-Ti intermetallics.It was revealed that the mechanical properties of the weld metal were controlled by the distribution and amount of Cu-Ti intermetallics.In light of the above results,the link among material-microstructure-mechanical property was built.