Preparation And Properties Of TiC-Reinforced Heterostructured Titanium Matrix Composites

Titanium alloys have high specific strength,corrosion resistance and biocompatibility and are widely used in aerospace,offshore exploration and other fields.With the rapid development of these fields,the demand for high-strength and hightenacity titanium alloy structural materials is increasing,and titanium matrix composites have become the inevitable choice for structural materials in the aerospace field due to their light weight,high strength and heat resistance properties.However,the rapid development of the aerospace field has posed higher challenges to the mechanical properties of titanium matrix composites.Based on this,this paper uses graphene(Gr)as a reinforcement precursor and uses its in situ interfacial reaction with the titanium matrix to generate a constructed network TiC reinforced composite to enhance the strength and plasticity of titanium matrix composites.To further improve the level of strong-plasticity balance of the composites,titanium matrix composites constructed with a heterogeneous matrix of TC18(Ti-5Al-5Mo-5V-1Cr-1Fe)and TC4(Ti-6Al-4V)/TA19(Ti-6Al-2Sn-4Zr-2Mo)in TiC-reinforced composites were constructed.The comprehensive improvement of the difficult problem of strongplasticity imbalance in titanium matrix composites.TiC-reinforced heterostructured titanium matrix composites were prepared by low-energy ball milling,spark plasma sintering(SPS)and hot rolling.X-ray diffraction(XRD),optical microscope(OM),scanning electron microscope(SEM),energy dispersive spectroscopy(EDS),electron back-scattered diffraction(EBSD)and electron probe micro-analyzer(EPMA)were used to study the phase composition,microstructure,morphology and distribution of the TiC-reinforced heterostructured titanium matrix composites.The mechanical properties of the composites were tested using a universal testing machine,and the fracture mechanisms of the composites in different states were analysed in combination with the fracture morphology,and the strong toughening mechanism of TiC-reinforced heterostructured titanium matrix composites was revealed.The main findings of this paper are as follows:The effect of Gr and TC18 content on the organisation and properties of TiC/(TC18+TC4)composites was investigated.It was found that as the Gr and TC18 content increased,the grains gradually refined,TC18 changed from a non-connected to a connected structure in them,and TiC gradually formed a discontinuous network structure at the grain boundaries.The transformation from a heterostructure to a laminated heterostructure was achieved using a hot rolling process.The tensile test results show that the tensile strength,elongation and homogeneous elongation of the rolled TiC/(TC18+TC4)heterostructured composites with 40 wt%(TC18+0.2 wt%Gr)/TC4 content are 1328 MPa,10.5% and 8% respectively,which are 47%,19% and77% higher respectively compared to the TC4 alloy.The TiC/(TC4+TC18)The sintered and rolled states of the TC18 composites are both hybrid fractures,with fracture originating from the soft zone grain boundaries around the TiC.The TiC/(TC4+TC18)composite has been comprehensively calculated to show that the strength improvement is dominated by heterogeneous deformation-induced hardening(HDI)strengthening,with fine grain strengthening and load transfer strengthening acting together;the plasticity improvement is through HDI strengthening,which increases the strain hardening rate.In order to further enhance the mechanical properties of TiC-reinforced heterostructured titanium matrix composites.In this study,TC4 was replaced with TA19 in the TiC/(TC18+TC4)composites.Since TA19 is stronger and contains more α-Ti,and TA19 contains β-type stabilizing elements,it is able to solid-solve with TC18 and promote the transformation of α-Ti to β-Ti during the hot rolling process.The results of the tensile test show that the tensile strength,elongation,and uniform elongation of the rolled 30 wt%(TC18+0.5 wt% Gr)/TA19 content TiC/(TC18+TA19)heterostructured composite are 1449 MPa,12.2%,and 7%,respectively.These values are 60% and 58%higher than those of the original TA19 alloy.The uniform elongation remains unchanged.The increase in strength is attributed to solid solution strengthening and the greater availability of α-Ti from TA19.The greater toughening is also due to a shift from α-Ti to β-Ti resulting from elemental diffusion.