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| Solid-state phase transformation of TC11 titanium during unstable thermal cycling in laser melting deposition process |
| Xiao-dong Li1, Jin Liu1, Yan-yan Zhu1, Xu Cheng1, Dong Liu1,2, Ji-kui Zhang3 |
| 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 100191, China;
2 Beijing Yuding Additive Manufacturing Research Institute Co., Ltd., Beijing 100096, China;
3 School of Aircraft Design, Beihang University, Beijing 100191, China |
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Abstract Thermal cycling during laser additive manufacturing (LAM) process causes the appearance of bright and dark patterns on the etched surface of TC11 alloy components. The formation mechanisms of these patterns and the solid-state transformation relating to LAM process are systematically investigated with the predication of temperature fields using the finite element software ABAQUS. The results indicate that by increasing numbers of subsequent thermal cycles, the peak temperatures for every cycle decrease. When the peak temperatures are above Tβ (1010 °C in TC11 alloy), no pattern is observed, and an ultrafine basket-weave α+β microstructure (darkly contrast) shows up in alloy with gradually increased number of α colony (decrease of peak temperatures). A special bimodal microstructure with 'fork-like' α lamellar appears in layer when the peak temperatures of thermal cycles firstly falls into α+β two-phase region. And this special bimodal microstructure gives a brightly contrast and only appears at the region when the peak temperatures are below 970 °C, leaving the rest region with a dark contrast. With the continuing increase of thermal cycles in the α+β two-phase region, α lamellar gradually coarsens. After five times thermal cycles in the α+β two-phase region, no further changes of microstructure are observed, the morphology of α lamellar in dark and bright regions are almost the same but with different amount of α phase.
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Received: 17 January 2018
Published: 15 July 2018
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| Cite this article: |
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Xiao-dong Li,Jin Liu,Yan-yan Zhu, et al. Solid-state phase transformation of TC11 titanium during unstable thermal cycling in laser melting deposition process[J]. Journal of Iron and Steel Research International, 2019, 26(7): 743-750.
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2019, Vol. 26 
