Study On Preparation And Strengthen Mechanism Of ZrO₂ Ceramic Particles Enhance Molybdenum Alloys

Molybdenum has so many advantages, such as high melting point, high density, high-temperature strength, high-temperature hardness and thermal conductivity, electrical conductivity and low expansion coefficient and superior mechanical properties, physical and chemical properties, are widely used in metallurgy, energy, machinery, chemicals, aerospace, defense, electronics and other fields, especially play an important role in high-tech fields. However, with the rapid development of modern industry, the products of traditional molybdenum are difficult to meet the needs of all walks of life. ZrO2 can increase the corrosion of molybdenum and temperature mechanical properties. Currently, both at home and abroad, there are few researches and reports on the hydrothermal synthesis method of Mo-ZrO2 alloy.This paper prepared Mo-ZrO2 billet by hydrothermal synthesis method and powder metallurgy method. The density and hardness of Mo-ZrO2 billet were tested; then Mo-ZrO2 billet were rolled into a thickness of 1.0mm plate. After annealing at different temperatures, the mechanical properties of Mo-ZrO2 plates are tested at room temperature. And the high temperature mechanical properties of Mo-ZrO2 plates are tested from 900 ℃ to 1200 ℃. The strain rate is set at 0.02 s-1 and 0.002 s-1,analysis the effect of ZrO2, temperature and strain rate on high-temperature properties of Mo-ZrO2 plates. XRD, SEM, EDS, TEM and other equipments were used to analyze the organization of Mo-ZrO2 billet, and the fracture morphology both at room and high temperature of Mo-ZrO2 plate. Eventually, the conclusions were showed as follows:ZrO2 eventually in the form of tetragonal phase exists in molybdenum powder and molybdenum alloys, ZrO2 particles play the role of refining the basic particles in all stages of the process. And with the increase of mass fraction of ZrO2, the particles size of molybdenum powder and molybdenum alloys are more and more smaller. With the content of ZrO2 increased, the hardness of molybdenum billet gradually increased, when the content of ZrO2 was within 1.0%, as the content of ZrO2 increased, the density of molybdenum billet gradually increased;when the content of ZrO2 was higher than 1.0%,with the increase of mass fraction of ZrO2, the density of Mo-ZrO2 billet gradually reduced. As the content of ZrO2 increasing, the tensile strength of Mo-ZrO2 plate obvious increase; with the annealing temperature rising, the tensile strength and hardness of Mo-ZrO2 billet gradually decreases, the fracture morphology of Mo-ZrO2 plate turned from the wood grain tear shape fracture into river pattern.At the same strain rate conditions, with the tensile temperature rising, the high temperature tensile strength gradually decreases. The fracture morphology of Mo-ZrO2 plate was dimple fracture from 900 ℃to 1200℃, however, after 1100 ℃pure molybdenum sheet’s fracture turn from the ductile fracture into brittle fracture; ZrO2 increased the recrystallization temperature of the molybdenum plate, expanding the use of molybdenum in the high temperature range. Under the same conditions, when the strain rate is higher, the molybdenum plate will has higher tensile strength and better plastic.