Deformation Mechanism And Mechanical Properties Of Titanium Alloy TA19

Titanium and its alloys are extensively utilized as critical structural materials in various fields due to their exceptional specific strength,toughness and corrosion resistance.The microstructure,crystal orientation and interaction between the two phases of titanium alloy are the key factors affecting the mechanical properties.However,these complex influences have not been carefully and systematically studied.In this work,TA19 titanium alloy was used as the research material.The different heat treatment systems were used to obtain the lamellar microstructure,equiaxed microstructure and bimodal microstructure,and these three types of microstrucrures were subjected to room temperature uniaxial compression.At the same time,the compression processes were observed in situ to obtain the evolution behavior of the slip traces and crystal orientations by combination of experimental characterization methods including scanning electron microscopy?SEM?,electron back-scattered diffraction?EBSD?.The main conclusions are summarized below:?1?Both higher Schimd Factor?SF? and lower Critical Resolved Shear Stress?CRSS?promote the slip initiation.However,at an angle?close to 90°between c-axis and applied stress directions,the sharply decreased Young's modulus arouses a difficult slip initiation in lamellar?even with a very high SF and low CRSS.?2?The slip always initiates in lamellar ? due to its lower yield strength and higher Young's modulus.In the study of the plastic deformation of the lamellar structure,the preferential slip initiation in interlayer?not occurs at a highest SF calculated based on the applied stress,because it is assisted by the internal stress.All8)^?between the preferential initiated slip in interlayer?and possible outgoing slip systems?Basal<a>,Prism.<a>,Pyr.<a>?in lamellar?are low.The slip transfer from interlayer?to lamellar?not only requires a good collaboration between SF and8)^?,but also needs an apparent accumulation of plastic deformation?slip?in interlayer?.?3?The crack could nucleate around the ?_GB and at the junction of several?colonies in the?grain during the compression,which is closely related to the difficult slip transfer between neighbouring grains(?_GB or?colony).The crack can propagates along the?_GB-?colony boundary,the junction between the?colony and slip plane.?4?The positions of of crack nucleation in the bimodal microstructure are mainly distribute between the lamellar structures and“hard grain”?the c-axis of the?grain is parallel to the applied stress direction?.With the plastic strain increasing,the nucleation of the crack no longer depends on the"hard grain".The slip is hard to transfer between grains and the position of stress concentration can contribute to the crack nucleation.During the plastic deformation process,it's possible that local stress is relaxed by twinning in TA19.