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| Effects of annealing temperature and cooling rate on microstructures of a novel titanium alloy Ti�C6Al�C2V�C1.5Mo�C0.5Zr�C0.3Si manufactured by laser additive manufacturing |
| Guo-chao Li1 ? Xu Cheng1 ? Xiang-jun Tian1 |
| 1 National Engineering Laboratory of Additive Manufacturing for Large Metallic Components and Engineering Research Center of Ministry of Education on Laser Direct Manufacturing for Large Metallic Components, School of Materials Science and Engineering, Beihang University, Beijing 100091, China |
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Abstract The microstructure changes of Ti�C6Al�C2V�C1.5Mo�C0.5Zr�C0.3Si alloy manufactured by laser additive manufacturing (LAM) are systematically investigated with statistical analysis of primary �� phase (�� p) and secondary �� phase (�� s) under different annealing conditions. Results indicate that, with the increase in holding temperature, the content of �� p lamellas decreases with the increasing as content, maintaining the total �� phases concentration stabilized. The width of �� p lamellas and the nominal specific surface area of �� phase both exhibit positive correlation with the temperature, while the increment of �� p and the widths of �� s lamellas show an increase�Cdecrease tendency. Besides, with the decrease in cooling rate, the total content of �� and the width of �� p lamellas increase, while the nominal specific surface area of a phase shows no significant change. The results indicate that, in the annealing process, the holding temperature determines the surplus and growth interfaces of �� p lamellas, and the cooling rate influences the nucleation quantity of �� s in unit time. During the cooling stage, the �� p lamellas grow initially, and then, the nucleation and crab-like structure growth occur followed by those of the �� s lamellas. The time intervals among them are influenced by cooling rate. The mechanism of microstructure formation of the LAMed titanium alloy during annealing stage was discussed, which would guide for the heat treatment method to achieve required microstructure.
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Received: 15 August 2017
Published: 15 October 2018
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2018, Vol. 25 
