Research On 2.5Vol.%TiBw/TA15 Composite Material Forging And Extrusion Process

Titanium alloy has been widely used in automobile,aerospace and other fields due to its high specific strength,good plastic toughness,excellent corrosion resistance and high temperature resistance.The in situ synthesis titanium matrix composite is based on titanium alloy to introduce ceramic phase enhancement,which can obviously strengthen the matrix due to the good and clean interface combination between the matrix and the reinforcing phase.However,the raw blank usually needs to undergo one or more thermoplastic deformation to obtain the required finished products or semi-finished parts.The subsequent thermal deformation is bound to have a huge impact on the structure and performance of the material,so it is necessary to study the thermal deformation technology of composite materials.Therefore,in this paper,TA15(Ti-6A1-2Zr-1Mo-1V)was used as the matrix alloy and Ti B as the ceramic reinforcing phase to prepare composite materials through hot isostatic pressure and hot pressing sintering process.The subsequent thermal deformation of the TiBw/TA15 composite was carried out by means of multi-direction isothermal forging,air hammer forging and hot extrusion,to explore the influence of different thermal deformation processes on the microstructure and mechanical properties of the TiBw/TA15 composite.In this paper,the isothermal forging process of the composite was firstly studied.The isothermal forging parameters were as follows: forging temperature 970 ?,strain rate 0.01/s.First of all,the composites prepared by the two methods are basically the same in the matrix,and are lamellar before forging,After forging,it was transformed into a two-state microstructure composed of primary ? and cluster ?,and the microstructure was refined.But hot isostatic pressing method in the process of the reaction sintering temperature is low,a large number of small size TiBw gathered in the grain boundary,affected the connectivity matrix,the matrix organization are refined after forging,strength of materials,received a significant boost from 920 MPa to 1100 MPa,but a large number of small size Ti B of barrier for strain coordination,and result in isothermal forging materials before and after the plastic is very poor,breaking elongation rate are less than 3%.As for the hot-pressed sintered composite material,TiBw grew well.After isothermal forging,the strength of the composite material increased from 975 MPa to 1124 MPa,elongation increased from 5.4% to7.8%,and the mechanical properties were significantly improved.Then,on the basis of isothermal forging research,air hammer forging experiment was carried out on the hot-pressed sintered composite material.The parameters of air hammer forging were as follows: forging temperature 1000 ?,each step of deformation was 10%,and the accumulated deformation was 60% and 100%respectively.After forging,the matrix structure changes to a two-state structure,and the increase of forging deformation is helpful to refine the grains of the composite.Too fast forging speed of air hammer will lead to fracture of some TiBw with large length to diameter ratio.In terms of mechanical properties,the strength and elongation of the composites with 60% deformation were 1018 MPa and 3.5%respectively,and the strength and elongation of the composites with 100%deformation were 1070 MPa and 4.9% respectively.Compared with before forging,the strength increased,but the plasticity decreased,mainly because the broken whisker would become the origin of crack initiation.Finally,the air hammer forging composite material with the accumulated deformation of 60% was tested by hot extrusion,and compared with the composite material under the hot pressing sintering+extrusion process,the extrusion temperature was 1000?,and the extrusion ratio was 10.6.After extrusion,the matrix of the composite material was transformed into a grain boundary ?,isoaxial ? phase and transformed ? tissue.TiBw was distributed in columnar network and oriented towards extrusion direction.The strength and elongation of the air-hammer forged+extruded composite material were 1183 MPa and 11.9%,and the mechanical properties were significantly improved.The TiBw/TA15 composite material only after extrusion was1193 MPa and the elongation was 9.8%.