The experimentation adopted low energy ball milling combining, with hot pressing sintering, to design and fabricate 3.4%(volume fraction)TiBw/TA15(Mo,Si) titanium matrix composites, for investigating the effects of heat treatment on the composites’ microstructure and mechanical properties. Through phase analysis about the composites via X-ray and transmission electron microscopy (TEM), while also analyzing the composites’ microstructure via scanning electron microscope, Several results the experimentation has observed. Firstly, the added TiB2 generated in-situ synthesized TiBw reinforcement which was distributed around the TA15 titanium alloy powder and formed a network microstructure. Moreover, fine (Ti,Zr)5Si3 reinforcement was formed by solid solution and precipitation mechanism and then Mo element was solid solution in β phase after MoSi2 solution at high temperature. Secondly, solution treatment with 1200 ℃ did not change the microstructure of TiBw neither the characteristics of the network microstructure of the composites, and the matrix was turned into martensite α'. (Ti,Zr)5Si3 reinforcement was re-dissolved and transformed to supersaturated solid solution. Thirdly, after aging treatment at 550-700 ℃, the martensitic matrix was decomposed, and the supersaturated silicon element was precipitated at the interface of both α/β interface and the network boundary. The acicular martensite α' was gradually transformed into lamellar (α + β) phase, and the amount of silicide precipitates was gradually increased with the increase of aging temperatures. Later, the experimentation further utilized Instron-5569 universal testing machine to test and analyze the composites’ mechanical properties. The experimental results show that the strength of titanium matrix composites is increased first and then decreased with the increase of aging temperature instead, and the plastic change is opposite to the strength change. The compressive strength of TiBw/TA15(Mo,Si) composites at 1200 ℃/45 min solution treatment is 1751 MPa, and the strain at break is 6.7%. After 1200 ℃/45 min solution treatment + 600 ℃/90 min aging treatment, the compressive strength of the composites reaches 1900 MPa and the strain at break decreases to 3.6%.
Effects of heat treatment on microstructure and mechanical properties of TiBw/TA15(Mo,Si)composites with network microstructure
2020
Article (Journal)
Electronic Resource
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