Effects Of Process,Particle Size And Element Content On The Structure And Properties Of TA18 Alloy

TA18(Ti-3Al-2.5V)is a low-alloy near-alpha(?+?)type titanium alloy,often referred to as"near-?"alloy.This alloy is often used in various types of aircraft due to its relatively excellent comprehensive properties,such as strong corrosion resistance and excellent welding performance.Powder metallurgy is an effective method to reduce the production cost of titanium and titanium alloys.However,the main disadvantage of traditional powder metallurgy is that defects such as residual pores in the material are difficult to eliminate,which leads to product performance degradation.The new process of using titanium hydride to manufacture titanium alloys may become the most promising method for reducing the production cost of titanium materials.This topic uses mixed element powder metallurgy technology to prepare Ti-3Al-2.5V,Ti-3Al-4V and Ti-5Al-4V alloys for the research by using two powdering methods.The first is to study the effects of sintering behavior and sintering parameters on the microstructure and mechanical properties of sintered samples,and secondly,to explore the effects of the content o f Al and V elements on the properties of sintered samples.The influence of sintering temperature and time parameter combination,alloy powder particle size distribution and other process factors on the relative density of sintered materials,grain size,s intered material structure,pore distribution,etc.,as well as mechanical properties are studied.When preparing Ti-3Al-2.5V by powder metallurgy,the structure of sintered sample becomes coarser with the increase of sintering temperature and time.The equiaxed organization showed a decreasing trend,while the flaky organization increased.Under the conditions of different sintering temperature,holding time,original powder particle size,and method of preparing alloy powder,the experimental results obtained for various samples show certain rules.From the point of view of the particle size of TiH₂ powder,in the two methods,the comprehensive performance of the strength and toughness of Ti-3Al-2.5V alloy obtained from 0?45?m TiH₂ is better than that of 0?88?m.From the point of view of holding time,the elongation after fracture of Ti-3Al-2.5V alloy with a holding time of4h is significantly higher than 8h,but the difference in tensile strength and yield strength is not particularly significant.From the point of view of two methods of making mixed powder,both have a slight advantage and disadvantage in the comparison of various properties,but from the change trend of the broken line,the alloy obtained after smelting is slightly worse than the 60Al-40V alloy powder mixed with elemental V powder.According to the experimental results,the best experimental condition for comprehensive performance is that the 45?m TiH₂ base is mixed with the master alloy powder prepared by smelting and kept at 1250?for 4h.At this time,the ultimate tensile strength of the sample is 874.87MPa,and the elongation after fracture is 20.80%.Using titanium hydride powder as a raw material to analyze the structure and mechanical properties of titanium alloys with different aluminum and vanadium contents,the following conclusions are obtained:as the contents of aluminum and vanadium increase,the diffraction peaks in XRD shift to a large angle and the crystal axis ratio increases.After the addition of aluminum and vanadium alloy elements,the corresponding titanium alloy sintered sample showed a flaky structure.With the increase of the content of Al and V elements,the strength of the prepared titanium alloy sample increased,and the elongation first showed a decreasing trend.The maximum tensile strength is 924.56MPa and 918.63MPa respectively,The maximum tensile strength at two temperatures are 924.56MPa and 918.63Mpa,and the corresponding elongations are 16.30%and 14.20%,respectively.Under the same conditions of aluminum and vanadium content,the elongation of the corresponding sintered samples at 1250?is slightly higher,and the comprehensive mechanical properties are slightly better.With the increase of aluminum and vanadium content,the brittle fracture morphology of the two types of alloys increases,the elongation decreases,and the plasticity decreases.