| High temperature materials have been widely used in various high temperature components for their powerful high temperature strength, good oxidation resistance, corrosion resistance, good fatigue properties and so on. Alloy strengthening method is one of the main traditional reinforcement approaches for the high temperature materials. Solid solution strengthening, aging strengthening and grain boundary strengthening realize the high-strength high temperature materials by adding the alloying element. Latest research shows that, there is a magnetic ordering strengthening in Fe-V alloy, even if below the Curie point, the high temperature strength is still high. It is a new type of high temperature materials worth to study. Therefore, according to the Fe-V binary phase diagram, Fe-V alloys are to be designed and mechanical properties of those alloys are to be determined, to provide a theoretical basis for the development of the new high-strength high-temperature Fe-V alloy.Three Fe-V alloys were designed and melt with a vacuum induction furnace, with the contents of4.01wt%V,12wt%V and16wt%V, respectively. The ingots were forged to20mm in thickness and then hot-rolled to3mm sheet. Tensile specimens after solution treatment and annealing were tested at the room temperature to determine desirable V content of the alloys. High temperature tensile test for Fe-V alloys with the optima V content were conducted to determine the mechanical properties. Effects of C/Cr addition on the high temperature mechanical properties of Fe-V alloys were studied, and composition and structure of surface oxide on Fe-V-Cr alloys were analyzed. The oxidation kinetics and oxidation mechanism of Fe-V alloys were investigated, and the antioxidant effect of Cr on Fe-V alloy were discussed.The results showed that:1. Results of tensile test at room temperature show that yield strength of Fe-V alloys increase with the contents of V increasing. For a lower content of V, σ0.2increases rapidly with the increase in V content. However, when the content of V is higher than4wt%,σ0.2increases slowly; the content of V is higher than12wt%, σ0.2does not change any more.2. For Fe-12V alloy, with the testing temperature both below600℃and above840℃, σ0.2decreases linearly with the tensile temperature increasing. For the testing temperature in the range of600℃and840℃, σ0.2decreases non-linearly and quickly with the tensile temperature increasing. There is a little difference from the previous two-stage linear decline results, and mechanism of non-linear change is expected to be further confirmed by experiments.3. Determination of M-T method and DSC results show that the addition of C into Fe-V alloy had no effect on the Curie temperature. XRD results revealed the addition of C and Crdid not change the characteristics of α-Fe (V) solid solution. The solid solution of C in Fe-V alloys can improve the yield strength of the Fe-V alloy.4. The relation between high-temperature yield strength and temperature change of Fe-V-C/Cr is the same as Fe-V alloy. The solid solution effect of the C is notable,5. At the same oxidation temperature, the oxidation resistance of Fe-V-Cr increase with the increase in Cr content. At the temperature of400℃and600℃, surface oxidation occurs with the production of Cr3O and similar oxide which inhibit the oxidation rate. The oxidation kinetics curve of Fe-V-Cr fit the parabolic rule well. At800℃, catastrophic oxidation occurs because of the generation of low melting point V oxide. The oxidation kinetics curve of Fe-V-Cr fit the linear rule. |
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