The Effect Of Multiple Enhancements On Grain Size And Properties Of Titanium And Titanium Alloys

Due to low density,high specific strength,excellent heat resistance and corrosion resistance,titanium and titanium alloy are widely used in aerospace,petrochemical industry,biomedical engineering and other fields.With the rapid development of science and technology,the demand for high strength titanium alloys is more and more urgent,therefore,the development of new titanium alloy with more excellent performance has become the main goal for many researchers.Titanium matrix composites?TMCs?has better mechanical properties than titanium alloys,providing a new opportunity for the development and application of titanium alloys.In this study,pure titanium and silicon are as raw materials,three kinds of titanium-silicon matrix alloys with different silicon content were prepared by vacuum suspended furnace?silicon contents were 2 wt.%,3 wt.%and 4 wt.%?.Optical microscope and scanning electron microscope were used to observe the microstructure of the alloys,the results showed that the addition of silicon could refine the pure titanium and the effect of grain refinement was more obvious with the increase of silicon content.The further study indicated that when the addition of silicon is 2 wt.%and 3 wt.%,weeny Ti₅Si₃ reinforcement?approximate 30 nm?would precipitate from titanium alloy during solidification,and reinforcement dispersed in the alloy uniformly.When the silicon content was 4 wt.%,the alloy would generate coarse Ti₅Si₃ reinforcement?approximate 10?m?,reinforcement segregated at grain boundaries and formed basketweave structure,it would impair the mechanical properties of the alloy.The mechanical property result of the alloy showed that adding silicon into pure titanium could improve the strength of pure titanium,but impair its plasticity of alloy.When the amount of silicon is 3 wt.%,the strength of the alloy would increase to 709±14 MPa from 388±9 MPa,the elongation of the alloy decreased from 18%to 1.45%,the improvement of mechanical properties of alloys was limited through the aging treatment.When the amount of silicon is2 wt.%,the strength of the alloy increased to 641±11 MPa,and the ductility could maintain above 13%.Due to the excellent plasticity of the alloy that adds 2 wt.%silicon,it was used as the matrix alloy to produce TMCs.In order to study the effect of multifarious reinforcement enhance alloy,adding B₄C particles with different content into matrix alloy,obtaining TMCs which contain Ti₅Si₃,TiB and other reinforcement.The mechanical properties of the composites analysis showed that,compared with pure titanium and matrix alloy,the hardness and wear resistance of material are obviously improved with the content of B4C particles increasing.The strength of the material increased from 641±11 MPa to 815±15 MPa,but the plasticity of material was reduced from 13.3%to 5.7%.It proved that multifarious reinforcement could enhance the strength,hardness and wear resistance of the alloys,but would reduce the plasticity of the alloys.