Microstructure Evolution and Pore Formation Mechanism of Porous TiAl3 Intermetallics via Reactive Sintering
来源期刊：Acta Metallurgica Sinica2018年第4期
论文作者：Xinyang Jiao Xiaohong Wang Peizhong Feng Yanan Liu Laiqi Zhang Farid Akhtar
文章页码：440 - 448
摘 要：Porous TiAl3 intermetallics were fabricated through vacuum reactive sintering from Ti–75 Al at.% elemental powder mixture. The phase compositions, expansion behaviors, pore characteristics and microstructure evolution of TiAl3 intermetallics were investigated, and the pore formation mechanism was also proposed. It was found that the actual temperature of compacts showed an acute climb from 668 to 1244 °C in 166 s, while the furnace temperature maintained the linear growth of 5 °C/min, which indicated that an obvious thermal explosion（TE） reaction occurred during sintering,and only single-phase TiAl3 intermetallic was synthesized in TE products. The open porosity increased from 22.2（green compact） to 32.8% after reactive diffusion sintering at 600 °C and rised to 58.7% after TE, then decreased to 51.2% after high-temperature homogenization at 1100 °C. Therefore, TE reaction is the dominated pore formation mechanism of porous TiAl3 intermetallics. The pore evolution in porous TiAl3 intermetallics occurred by the following mechanisms:certain intergranular pores remained among powder particles of green compact, then low-temperature sintering resulted in a further increase in porosity due to the Kirkendall effect. Moreover, TE reaction gave rise to a dramatic volume expansion because of the rapid increase in temperature, and high-temperature sintering caused densification and a slight shrinkage.
Xinyang Jiao1,2，Xiaohong Wang1，Peizhong Feng1，Yanan Liu1,2，Laiqi Zhang3，Farid Akhtar4
1. School of Materials Science and Engineering, China University of Mining and Technology2. School of Chemical Engineering and Technology, China University of Mining and Technology3. State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing4. Division of Materials Science, Lule? University of Technology
摘 要：Porous TiAl3 intermetallics were fabricated through vacuum reactive sintering from Ti–75 Al at.% elemental powder mixture. The phase compositions, expansion behaviors, pore characteristics and microstructure evolution of TiAl3 intermetallics were investigated, and the pore formation mechanism was also proposed. It was found that the actual temperature of compacts showed an acute climb from 668 to 1244 °C in 166 s, while the furnace temperature maintained the linear growth of 5 °C/min, which indicated that an obvious thermal explosion（TE） reaction occurred during sintering,and only single-phase TiAl3 intermetallic was synthesized in TE products. The open porosity increased from 22.2（green compact） to 32.8% after reactive diffusion sintering at 600 °C and rised to 58.7% after TE, then decreased to 51.2% after high-temperature homogenization at 1100 °C. Therefore, TE reaction is the dominated pore formation mechanism of porous TiAl3 intermetallics. The pore evolution in porous TiAl3 intermetallics occurred by the following mechanisms:certain intergranular pores remained among powder particles of green compact, then low-temperature sintering resulted in a further increase in porosity due to the Kirkendall effect. Moreover, TE reaction gave rise to a dramatic volume expansion because of the rapid increase in temperature, and high-temperature sintering caused densification and a slight shrinkage.
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