Research On High And Room Temperature Properties Of Oxide Particles Dispersion Strengthened Pt-Rh Alloys And Its Welded Joints

Platinum and its alloys have excellent corrosion resistance,high temperature stability,and creep resistance,which can be manufactured precision electrical contact materials,resistance thermometers,catalysts,bushing plate,glass liquid channel and so on.Platinum and its alloys are widely used in the electrical industry,chemical industry and fiberglass industry.Grains of common platinum and its alloys grow easily in high temperature stress environment,and the properties drop down dramatically,it is difficult to meet the increasingly stringent requirements of service performance.Research and engineering practice at home and abroad show that solid solution strengthening and dispersion strengthening can effectively improve the room temperature properties and high temperature properties of platinum alloys.In this paper,platinum alloys,the commonly used materials for bushing plate in fiberglass industry,are taken as the research object.The service performance of the bushing plate is improved by solid solution strengthening and dispersion strengthening.The microstructures,mechanical properties at room temperature,high temperature creep resistances and wettabilitys of Pt-20Rh-0.015Y-xZr（x=0,0.4）alloys and its welded joints are studied.The main work and research results are as follows:（1）1 mm thick Pt-20Rh-0.015Y-xZr alloys flakes are prepared by powder metallurgy,internal oxidation-sintering,high temperature forging,rolling and annealing processes,and they are welded by manual argon arc welding.（2）The microstructure characteristics of alloys and its welded joints are observed and analyzed by metallographic microscope.The results show that TD-RD grains of the rolled Pt-20Rh-0.015Y-xZr alloys exhibit a large aspect ratio along the fibrous structure.The grain aspect ratio of Pt-20Rh-0.015Y-0.4Zr alloy is greater than that of Pt-20Rh-0.015Y alloy.The macroscopic surfaces of Pt-20Rh-0.015Y-xZr alloys welded joints are smooth and have high density.The strengthening phase particles appeared on the surface of Pt-20Rh-0.015Y-0.4Zr alloy welded joint are significantly more than Pt-20Rh-0.015Y alloy welded joint.The grain size of WNZ in the weld joint is larger,and the grain size of WNZ in the Pt-20Rh-0.015Y alloy weld joint is larger than that of Pt-20Rh-0.015Y-0.4Zr alloy weld joint.The inner side of TMAZ is mainly coarse columnar crystals and the outer side is mainly equiaxed crystals.HAZ undergoes recrystallization.The grain size in HAZ of Pt-20Rh-0.015Y-0.4Zr alloy welded joint is about 4.9μm,and the grain size in HAZ of Pt-20Rh-0.015Y alloy welded joint is about 13.2μm.（3）The mechanical properties of the alloys and its welded joints are tested at room temperature,the results show that the tensile strength and yield strength of Pt-20Rh-0.015Y-0.4Zr alloy are 589 MPa and 310 MPa,higher than Pt-20Rh-0.015Y alloy by 43.0%and 116.8%,respectively.The mechanical properties of Pt-20Rh-0.015Y-xZr alloy welded joints decrease to some extent compared with base metal.The tensile strength and yield strength of Pt-20Rh-0.015Y-0.4Zr alloy welded joints are 483MPa and 297MPa,higher than Pt-20Rh-0.015Y alloys welded joints by 21.1%and 77.8%,respectively.The tensile fracture of base metal at room temperature contains a large number of dimples,which are plastically fractured.The strengthening phase particles exist in the fractured dimples of Pt-20Rh-0.015Y-0.4Zr alloy.The EDS energy spectrum analysis shows that the main component of the particle is ZrO₂.The number of dimples in the fracture of welded joints is significantly lower than that of the base metal,and the plastic fracture characteristics is weaker than the base material.（4）Creep resistance of alloys and its welded joints are tested at 1400°C,20MPa,the creep lasting time of Pt-20Rh-0.015Y-0.4Zr alloy and its welded joint are 11.7 and 0.46hours,which are 21 times and 2 times of Pt-20Rh-0.015Y alloy and its welded joint,respectively.Recovery and recrystallization of Pt-20Rh-0.015Y-xZr are obvious under high temperature and high load.There are few dimples on the creep fracture surface of Pt-20Rh-0.015Y-xZr alloys and its welded joints,strengthening phase particles are found in creep fractures of Pt-20Rh-0.015Y-0.4Zr alloy and its welded joint.The EDS spectrum analysis shows that the main component of the particle is ZrO₂.Stripes of suspected dislocation loops appear in the fracture of Pt-20Rh-0.015Y-0.4Zr alloy and welded joint.（5）The wettabilitys of Pt-20Rh-0.015Y-xZr alloys with the TM⁺glass droplets are tested by sessile drop method at 1000-1550°C.In this temperature range,the wetting angle decreases as the temperature increases.At 1050°C,the wetting angles are 148.6°and 142.0°,respectively,not wetting.At the 1550°C,the wetting angles are 63.5°and67.3°,respectively,the wettability is good.