Abstract
The microstructure and mechanical properties of Ti-2Si-2Nb-2Fe-1Hf-1Ta-1W alloy with (TiHf)5Si3 particle-reinforcement and their underlying relations have been studied. Electron microscope observations and correlative statistical analysis have been made to analyze microstructure evolution with heat treatments. The (TiHf)5Si3 particles with 800 nm in diameter were found uniformly distributed at α/β boundaries and triple junctions and turned out to be stable even after heat treatments at high temperature for a long period, inhibiting grain growth and dislocation motion. In addition, multi-strengthening-mechanisms including particle strengthening, solid-solution strengthening, grain boundary strengthening and dislocation strengthening have been discussed.
Highlights
Titanium and its alloys are widely used as an important class of engineering materials in aerospace, nuclear, chemical plants and biomaterials fields due to their high strength-to-weight ratio and good corrosion resistance [1, 2]
The overall microstructure of as-rolled sample is shown in Figure 1(a), showing fine equiaxed grains with uniform distribution of particle reinforcements
The microstructures of the Ti alloys after different heat treatments are shown in Figure 2, showing that the average size of the particles does not change much with a slight growth to 1 μm
Summary
Titanium and its alloys are widely used as an important class of engineering materials in aerospace, nuclear, chemical plants and biomaterials fields due to their high strength-to-weight ratio and good corrosion resistance [1, 2]. High volume fraction of Ti5Si3 phase may depress the plasticity of the Ti alloys at room temperature due to its brittleness. Increasing needs of the Ti alloys with good performances invoke widespread investigations on the relationship between microstructure and properties of newly designed silicon-containing Ti alloys. Ti-Si-X alloys with β-stabilizing elements have been proposed and exhibited improved plasticity [6, 7]. Our previous work proved that the comprehensive mechanical properties of silicon-containing Ti alloys could be improved by adding multiple alloying elements including Nb, Fe, Hf, Ta and W [8]. The relationship between microstructure and properties and the underlying strengthening mechanisms of these Ti alloys have not been investigated sufficiently
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