Study On Canned Hot Extrusion Preparation And Microstructure And Mechanical Properties Of TiB Whisker Reinforced TB8

As a structural material with high specific strength,excellent high temperature resistance and corrosion resistance,titanium alloy has increasingly become the research focus.However,in the course of its development,there is still a problem that the application scenario is limited because the strength is not high enough.The way to add the reinforcement phase is an effective way to improve its comprehensive performance.However,in the current research of composite materials,the main researches are the near-? and ?+? titanium alloys such as TC4 and TA15.As a high-strength ? titanium alloy,further strengthening its performance is an inevitable demand for expanding its application,but currently there are few related studies.Aiming at the existing problems,this paper selects TB8 alloy as the matrix,selects common Ti B whiskers as the reinforcement phase,and studied the material preparation,microstructure and mechanical properties of whisker reinforced ? titanium alloy.Firstly,the performance range and strengthening mechanism of TB8 alloy were studied.The results showed that the ? precipitation phase affected the strength of the material and the ? phase controlled the plasticity of the TB8 alloy.After solution treatment at 850 ?,only the ? phase existed in the microstructure,and the tensile strength was 820 MPa and the elongation was 15.1%.After aging at 500 ?,the content of secondary ? precipitates was gradually increased with increasing the aging time,and the microhardness of the material was also increased.After 12 h aging,the tensile strength reached 1470 MPa,and the elongation was only 1.7% due to a large number of precipitations of secondary ? phase.In general,the strengthening mechanism of TB8 alloy was the precipitation strengthening of the secondary ? phase formed by aging,and the experimental results also showed its excellent performance adjustability,which was suitable for common technical routes such as cold plastic forming and heat treatment strengthening.The Ti Bw/TB8 titanium matrix composites were prepared by low energy milling plus pre-sintering plus powder hot extrusion.The effect of extrusion temperature on the microstructure and properties of the material was systematically studied.It was found that for the reinforcing phase,when the extrusion temperature was 800 ? and 900 ?,the aspect ratio of the Ti B phase was extremely small.When the extrusion temperature was increased to 1000 ?,the aspect ratio of the Ti B phase is significantly increased,and the long axis direction of the whisker was parallel to the extrusion direction;After the addition of the Ti B phase,significant grain refinement occurred.When the extrusion temperature is 800 ? and 900 ?,the deformation occurred in the ?+? phase region,and the primary ? phase,Ti B phase and ? phase existed in the room temperature microstructure.When the extrusion temperature was raised to 1000 ?,the primary ? phase disappeared,but due to the slow cooling rate,a large number of grain boundary ? phases were precipitated.Due to the sufficient dynamic recrystallization in the microstructure,no obvious texture was found in the room temperature microstructure.From the performance point of view,when the extrusion temperature was 800 ? and 900 ?,the composites fractured in the elastic deformation stage due to the existence of a large number of Ti B phases with a small aspect ratio.When the extrusion temperature was raised to 1000 ?,the grain boundary brittleness happened due to the grain boundary ? phase,although the tensile strength reached 1200 MPa,the ductility is only 2.1%.Based on the understanding of the microstructure and properties of TB8 alloy itself,the effect of heat treatment on the microstructure and properties of extruded Ti Bw/TB8 titanium matrix composites was investigated.First,after ? solution and water cooling,the formation of the grain boundary ? phase was effectively suppressed,only the ? phase and the Ti B phase remained in the microstructure.Due to the disappearance of the grain boundary ?,although the tensile strength of the composite was lowered to 1150 MPa,the elongation was greatly increased from 2.1% to 10.1%.On this basis,the composites were aged at 500 ? to study the effect of aging time on the microstructure and properties of the composites.The results showed that,like TB8 alloy,a large amount of acicular secondary ? phase precipitates in the aging material,and with the aging time prolonged,the microhardness first increased and then gradually stabilized.When the aging time was 2 hours,the tensile strength of the composite was 1495 MPa and the elongation was 4%.