Effect Of Ta On The Microstructure And Mechanical Properties Of W-Ta Alloys Prepared By Arc Melting

Tungsten（W）has excellent physical and chemical properties such as high melting point,high density,high strength and so on.It has a wide application prospect in nuclear industry,electronic industry,aerospace and other fields.However,due to the brittleness of W at room temperature,its machining performance is poor,which limits the further application of W material in practical engineering.The strengthening and toughening of W are the core issue in its application as a structural material.In this paper,from the perspective of solid solution strengthening and toughening of W,the method of cold isostatic press-arc melting was used to prepare high melting point and high density of W solid solution alloy.The W-x Ta（x=0,10,20,30,40,and 50 wt.%）alloy system was prepared based on the optimized smelting process.The effect of Ta content on microstructure evolution and mechanical properties at room temperature/high temperature was studied,the microstructure and deformation mechanism of W-40Ta alloy in arc melting state,room temperature compression state and high temperature compression state were studied,and the effect of Re element addition on microstructure and mechanical properties of W-40Ta alloy was further discussed.The main research results of this paper are as follows:（1）The average grain size of pure W in arc melting is about 1 mm.When Ta addition is 50 wt.%,the average grain size of W-Ta alloy decreases to 243μm.Ta alloying has a good grain refining effect.The grain size of pure W in arc melting is about 1 mm,the average grain size of W-Ta alloy decreases to 243μm when Ta addition is 50 wt.%.Under the synergistic effect of grain refinement and Ta solution effect,the hardness of W-40Ta alloy reaches 614.3 HV_0.5,the compressive strength reaches1627 MPa at room temperature,and the compressive strain reaches 13.1%.The strain capacity of W-40Ta alloy is nearly two times higher than that of melted pure W（4.5%）.The high temperature compressive strength of pure W is 205.6 MPa at 1000℃,and the high temperature compressive strength of W-40Ta alloy is 524.3 MPa,increased by 155%.The addition of Ta element can improve the hardness and compressive performance,and W-40Ta has the best comprehensive mechanical properties.（2）The deformation mechanism of W-40Ta alloy is transformed into the synergistic effect of edge dislocation slip and screw dislocation slip.The dislocation density of the compressed W-40Ta alloy is significantly higher than that of pure W.Besides screw dislocation slip,edge dislocation slip is also found to be an important slip mechanism in W-40Ta alloy.After1000℃high temperature compression of W-40Ta significantly increased the grain in the dislocation density of Ta alloy,produced a large number of dislocation and dislocation tangle,it mainly comes from high temperature deformation caused by the relative movement and the happening of the inhomogeneous strain,continuous strain cause dislocation multiplication,dislocation by grain boundary in the process of movement at the same time,produce stuffed dislocation and dislocation tangle.（3）The addition of Re element has a certain toughening effect on W-40Ta alloy.Re alloying results in the decrease of hardness and compressive strength of W-40Ta-x Re alloy,and the increase of compressive strain.When the Re content increases to 10%,and the compressive strain increases from 13.42%to 14.36%.The Compression fracture mode of W-40Ta-5Re and W-40Ta-10Re is consistent with that of W-40Ta,and also presents a mixed fracture mode of transgranular cleavage and intergranular fracture.There are 49 pictures,11 tables,128 references in this thesis.