Research On The Structure And Properties Of In-situ (TiC, TiB)/Ti-based Composites

Titanium matrix composites have excellent mechanical properties,corrosion resistance,and biocompatibility,they are widely used in aerospace,marine,navigation and medical fields.In this paper,we use the Mo₂C powder,MoB₂ powder,pure titanium powder and Mo powder as raw materials to prepare TiC/Ti matrix composite materials and TiB/Ti matrix composite materials by in-situ reaction.The volume content of reinforcement in composites is 1.38 vol%,2.8 vol%,and 4.2 vol%.The purpose of this article is exploring the effects of different sintering temperatures on the mechanical properties of composites and then determining the optimal sintering temperature.Probing the effects of the volume content of the reinforcement on the microstructure and mechanical properties of the composite to determine the optimal volume content of the reinforcements.And then to reparation?TiC+TiB?/Ti matrix composites,to find the effects of the ratio of TiC:TiB in the composites on the structure and properties,research of the strengthening difference of mechanical properties between the single reinforced phase and composite reinforced at the same Mo content and volume fraction.First,we investigate the influence of sintering temperature on TiC/Ti matrix composites.The experimental results show that when the sintering temperature is increased from 1200? to 1300?,the relative density values of composites reach more than 98%,increasing significantly and relevent with TiC particle content.The mechanical property results show that the effect of sintering temperature on the Rockwell hardness and compressibility of TiC/Ti-based composites is related to the content of Mo₂C.With the increase of Mo₂C content,the Rockwell hardness and compressibility of the composite material increased significantly when the sintering temperature was increased.However with rising the sintering temperature,the relative density,Rockwell hardness,and compressive strength of TiB/Ti matrix composites all improve significantly.Therefore,in this experiment,the temperature is 1300? and maintain for 90 minutes,the prepared TiC/Ti matrix composites and TiB/Ti matrix composites have the best mechanical properties.The XRD patterns of TiC/Ti matrix composites can clearly find that the?-Ti,?-Ti and TiC phases.,and the intensity of the?-Ti and TiC phases increase by the addition of Mo₂C.The SEM and OM picture can find out the microstructure of composites that TiC particles shape are mainly equiaxed and nearly equiaxed and almost distributed at grain boundaries,and the matrix grain size were refined by TiC.Rockwell hardness test results reveal that the content of reinforcing phase increased from 1.37 vol%to 4.2 vol%,and the Rockwell hardness of TiC/Ti matrix composites upgraded from 26.3 HRC to 35.2 HRC,which were 13.3%and 18.2%higher than the identical content of Mo of Ti-Mo alloy.Compression experiments results show that the addition of Mo₂C can effectively improve the yield strength,ultimate compressive strength and fracture strain of the composites.As the content of the reinforcing phase increases,the yield strength of the TiC/Ti matrix composites increases from 976.1MPa to 1435.6 MPa.The strengthening mechanism of composite materials is mainly solid solution strengthening,TiC phase strengthening,and fine grain strengthening.The XRD pattern of TiB/Ti matrix composites shows that?-Ti,?-Ti and TiB phases are present in the composite.The microstructure results of composite materials by SEM and OM exhibit that topography of TiB in the composite material is mainly short-fibrous.the Rockwell hardness of the composite material has increased from36.3 HRC to 39.9 HRC,compared with the corresponding Ti-Mo alloy that the hardness values have been escalated 38.0%and 13.4%%.In the compressive properties of TiB/Ti matrix composites,the yield strength and ultimate compressive strength move up with increasing TiB content,and the yield strength is increased from1262.3 MPa to 1451.3 MPa,which is 41%and 17%higher than the corresponding Ti-Mo alloy,however the fracture strain decreases sharply.Therefore,a small amount of TiB can significantly improve the yield strength of titanium materials.The strengthening mechanism of composite materials is mainly solid solution strengthening,TiB phase strengthening and fine grain strengthening.The XRD patterns of?TiC+TiB?/Ti matrix composites show that?-Ti,?-Ti,TiC and TiB phases are present in the composite.The compression performance results show that the properties of?TiC+TiB?/Ti matrix composites are between the corresponding TiB/Ti matrix composites and TiC/Ti matrix composites.The higher the TiC ratio,the higher the strength of the composite and the A certain fracture strain,where TiC:TiB=2:1,?TiC+TiB?/Ti matrix composites have the best compressive properties.