Effect Of Hot Rolling And Thermal Diffusion On The Structure And Properties Of PtTi0.5Zr0.2 / Ti Composite Composites

Pt-based material with a high melting point, excellect thermostability, inoxidizability, the corrosion-resistant, high temperature strength properties and biocompatibility, has been widely used in modern industry, national defense science and technology, biotechnology and so on. The application of platinum is limited by the low intensity and high price. Pt-based laminated composite material can improve the mechanical properties and save production cost.In the present work, PtTi0.5Zr0.2/Ti metal matrix laminated composite material is prepared by heat pressing combined with hot and cold rolling technology and then to proceed high temperature diffusion and medium temperature heat treatment. The effect of large deformation rolling (>90%) and thermal diffusion treatment on microstructure and properties of laminated composite material is analyzed by optical microscopy(OM), scanning electron microscopy(SEM), X-ray energy dispersive spectrometer, electronic universal testing machine and micro-hardness examine. The results are summarized as following:(1) PtTi0.5Zr0.2/Ti laminated composite materials prepared by850℃/2h hot pressing and cold rolling (the thickness of PtTi0.5Zr0.2layer is14μm, Ti layer is8μm) can obtain more uniform deformation microstructure and better parallelism than that processed by hot pressing at850℃/2h and rolling at200℃/300℃; PtTi0.5Zr0.2/Ti laminated composite materials prepared by hot pressing at500℃/2h and cold rolling can obtain the microstructure with good continuity and uniform straightness, however, laminated composite materials prepared by hot pressing at500℃/2h and rolling at500℃(the rate of layer thickness is14:8and20:8, respectively) obtain the microstructure with good continuity and weak uniform and parallelism. In general, the metal layer of PtTi0.5Zr0.2/Ti laminated composite materials obtained by hot pressing at500℃/2h and cold rolling is good continuity, uniform and parallelism. The parallelism, uniform and continuity of the large deformation PtTi0.5Zr0.2/Ti laminated composite materials are better than Pt/Ti laminated composite materials, the result that suggest Ti, Zr microalloyed can significantly improved continuity, uniform and parallelism of laminated composite materials.(2) PtTi0.5Zr0.2/Ti laminated composite materials is processed by high temperature diffusion from850℃to1400℃(1h), Pt and Ti atom of laminated composite materials diffusion reaction gradually increased with increasing temperature, Ti layer and PtTi0.5Zr0.2layer gradually reduced to disappear, β-Ti phase and Ti3Pt, PtTi, Pt3Ti intermetallic compound layer appear in interface. The low melting point intermetallic compound gradually transform to the high melting point intermetallic compound with increasing temperature, when the temperature is1400℃, only Pt3Ti and PtTi intermetallic compound formed in interface. When the diffusion time increases from1h to7h (the temperature is850℃), the intermetallic compound layer gradually increased and Ti layer gradually disappear, but PtTi0.5Zr0.2layer always remains. When the temperature increase from500℃to750℃(1h), laminated composite materials processed at500℃hot pressing began to form obvious intermetallic compound, and the thickness of intermetallic compound layer gradually increase with increasing temperature, the relationship between thickness and temperature is linear increasing. When the time increase from1h to5h (700℃), the thickness of intermetallic compound layer gradually increase with increasing time, but the degree of increase is gradually decreases. The result indicated the effect of temperature on intermetallic compound formation is more obvious than that of time during thermal diffusion.(3) PtTi0.5Zr0.2/Ti (the rate of thickness is14:8) laminated composite materials, the tensile strength is676.8MPa and the elongation is9.6%, which is prepared by500℃/2h hot pressing and500℃rolling processing. The tensile strength and elongation is larger than PtTiO.5Zr0.2/Ti laminated composite materials prepared by500℃/2h hot pressing and cold rolling processing and prepared by850℃/2h hot pressing and cold rolling processing. The tensile strength and elongation of PtTi0.5Zr0.2/Ti laminated composite materials (the thickness rate is20:8) is788.1MPa and8%, respectively. At cold-rolling condition, the tensile strength and elongation of the processing state laminated composite materials are improved through500℃/1h thermal diffusion, but the tensile strength and elongation reduced at warm-rolling condition. The tensile strength and elongation of laminated composite materials processed at different processing conditions decrease as thermal diffusion temperature increase from500℃to750℃(1h). The tensile strength and elongation of laminated composite materials processed at different processing conditions decrease as thermal diffusion time increase from1h to5h (700℃). Comparison different processing, the tensile strength of laminated composite materials(the rate of layer thickness is20:8) prepared at500℃/2h hot pressing and500℃rolling is highest, however, when the layer thickness rate of PtTi0.5Zr0.2/Ti is14:8, the laminated composite materials processed at same processing conditions, the elongation is highest.