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The Heat Treatment Influence on the Microstructure and Hardness of TC4 Titanium Alloy Manufactured via Selective Laser Melting

1
School of Materials Science and Engineering, North University of China, Taiyuan 030051, China
2
School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Materials 2018, 11(8), 1318; https://doi.org/10.3390/ma11081318
Received: 21 June 2018 / Revised: 27 July 2018 / Accepted: 28 July 2018 / Published: 30 July 2018
(This article belongs to the Special Issue Additive Manufacturing: Alloy Design and Process Innovations)
In this research, the effect of several heat treatments on the microstructure and microhardness of TC4 (Ti6Al4V) titanium alloy processed by selective laser melting (SLM) is studied. The results showed that the original acicular martensite α′-phase in the TC4 alloy formed by SLM is converted into a lamellar mixture of α + β for heat treatment temperatures below the critical temperature (T0 at approximately 893 °C). With the increase of heat treatment temperature, the size of the lamellar mixture structure inside of the TC4 part gradually grows. When the heat treatment temperature is above T0, because the cooling rate is relatively steep, the β-phase recrystallization transforms into a compact secondary α-phase, and a basketweave structure can be found because the primary α-phase develop and connect or cross each other with different orientations. The residence time for TC4 SLM parts when the treatment temperature is below the critical temperature has little influence: both the α-phase and the β-phase will tend to coarsen but hinder each other, thereby limiting grain growth. The microhardness gradually decreases with increasing temperature when the TC4 SLM part is treated below the critical temperature. Conversely, the microhardness increases significantly with increasing temperature when the TC4 SLM part is treated above the critical temperature. View Full-Text
Keywords: selective laser melting; titanium alloy; heat treatment; microstructure; microhardness measurement selective laser melting; titanium alloy; heat treatment; microstructure; microhardness measurement
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MDPI and ACS Style

Zhao, Z.-Y.; Li, L.; Bai, P.-K.; Jin, Y.; Wu, L.-Y.; Li, J.; Guan, R.-G.; Qu, H.-Q. The Heat Treatment Influence on the Microstructure and Hardness of TC4 Titanium Alloy Manufactured via Selective Laser Melting. Materials 2018, 11, 1318.

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