The Effect Of Hot Isostatic Holding Temperature On Microstructure, Mechanical Properties And Corrosion Behavior Of TC4 Alloy

With the rapid development of modern industry,people have higher requirements for the performance of titanium alloy materials so as to meet the applications under complex conditions.TC4,As the most widely used(?+?)type titanium alloy,has been widely concerned.In the traditional Processing technology such as casting,forging and machining processes,due to the serious waste of raw materials,low production efficiency,high production costs,and difficult to control size and accuracy would affect its applications.Hot isostatic pressing technology has been gradually applied to the preparation of TC4 alloy components for its high production efficiency,high preparation accuracy and diversity of products.The research on TC4 alloys prepared by hot isostatic pressing is often limited to a single temperature and pressure,and there is no complete presentation of the changes in the microstructure,phase comparison and properties of the alloys at different hot isostatic pressing temperatures.In this paper,the microstructure,mechanical properties,and electrochemical corrosion characterization of TC4 alloys prepared at different hot isostatic holding temperatures are systematically investigated.The effects of hot isostatic holding temperatures on the mechanical properties of TC4 alloys and the influence of heat treatment process on microstructure evolution The influence of microstructure on the corrosion behavior of alloys.By analyzing the effect of the hot isostatic holding temperature on the microstructure,tensile and compressive properties of the TC4 alloy,it is shown that with the increase of the hot isostatic holding temperature,the density of the alloy gradually increases,and the volume of the ? phase in the microstructure gradually increases,and the distribution tends to be uniform;under the conditions of 120 MPa and 2h holding pressure,when the hot isostatic holding temperature is higher than 800°C,the density of the alloy can reach more than 99%,and there are no obvious holes in the microstructure.With the increase of the hot isostatic holding temperature from 800°C to 920°C,the room temperature tensile strength of the alloy decreased from 942 MPa to 920 MPa,and the tensile strain increased from 13.7% to 18.1%;the room temperature compressive strength decreased from 1280 MPa To1158MPa,the amount of strain increased from 14.5% to 32.4%.The increase of ? phase is the main reason for the decrease of alloy strength and plasticity.The TC4 alloy with good comprehensive mechanical properties after hot isostatic pressing at 920?/120?/2h was used for the subsequent heat treatment process research.By changing the heating temperature and cooling rate,the morphology and microhardness of the alloy after heat treatment were compared and analyzed.It can be known that with the increase of heating temperature and cooling rate during heat treatment,the microhardness of the alloy increases significantly.The hardness value of the TC4 alloy quenched after holding at 1100? for 1hour can reach 391 HV.The block-like ?'-martensite phase formed during the quenching makes the TC4 alloy have a higher hardness.Electrochemical corrosion tests were performed on three TC4 alloys with high density after hot isostatic pressing.The results show that TC4 alloys with the hot isostatic pressing process at 920?/120?/2h have the best corrosion resistance.The current is 0.8613?A,and the comprehensive impedance is 4.48M?.The high isostatic pressing temperature keeps the alloy's microstructure uniform and the ? phase volume fraction in the alloy increasing,which effectively improves the corrosion resistance of the alloy.