The Positive Effect of Hydrogen Alloying on the Phase Tailoring and Mechanical Properties of Sintered Ti-13Nb SMAs
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The effect of hydrogen alloying on phase tailoring and mechanical properties of the sintered Ti-13Nb (at pct) shape memory alloy (SMA) was investigated. It was found that hydrogen addition changed the microstructure of the sintered Ti-13Nb-(0-31)H (at pct) alloys gradually from α + β dual phase to single β phase due to the lowered transition temperature of β phase to α phase by hydrogen action. The reduction of α phase precipitation in the alloy reduced the amount of Nb squeezed out from the Nb-depleted α phase, and consequently decreased the mean Nb content in the β phase. Thus, the Ms temperature of Ti-13Nb alloy was successfully increased from lower temperature to near room temperature, which consequently enhanced the recoverable strain of the alloy by easier martensitic transformation. The sintered Ti-13Nb-18H alloy presented a Ms temperature of 22 °C and a remarkable recoverable strain of 3.9 pct at room temperature, which is the highest value ever reported in the sintered Ti-Nb based SMAs. Meanwhile, the Ti-13Nb-18H alloy exhibited a fracture strain of 23.1 pct and a fracture strength of 1321 MPa, both better than that of the Ti-13Nb alloy, which was attributed to the hydrogen atoms in the alloy which caused solid solution strengthening and also increased the content of the β phase with higher plasticity.
The authors would like to acknowledge the financial support from Guangdong Provincial Science and Technology Projects (2016A030311012) and Key Laboratory of Advanced Energy Storage Materials of Guangdong Province.
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