☆ 4.7 Article

Influence of hydrogenation on microstructures and microhardness of Ti6Al4V alloy

TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA (2008)

Journal

TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA

Volume 18, Issue 3, Pages 506-511

Publisher

ELSEVIER SCIENCE BV

DOI: 10.1016/S1003-6326(08)60089-8

Keywords

Ti6Al4V alloy; hydrogenation; hydride; microhardness; defect; solution strengthening; diffusion

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Abstract

The microstructures of Ti6Al4V alloy after hydrogenation were investigated by optical microscopy(OM), X-ray diffraction(XRD) and transmission electron microscopy(TEM). The influence of hydrogenation on the hardness of alpha and beta phases was analysed by microhardness testing. The influence of hydrogenation on alloying elements diffusion was studied by electron probe microanalysis(EPMA). The microstructural observation reveals that hydride delta (FCC structure) as well as large number of dislocations precipitate in the specimens with 0.278% and 0.514% hydrogen, and a lot of twins are found in the specimen with 0.514% hydrogen, simultaneously. The result of microhardness testing shows that the hardness of alpha and beta phases increases synchronously with the increase of hydrogen and the hardness increment of beta is larger than that of alpha. According to analysis of EPMA, the diffusion ability of alloy elements Al and V increases after hydrogenation. It is considered that hydrogen solution strengthening and V element diffusion are the main factors causing the hardness of a phase increase with the increase of hydrogen, and the formation of delta hydrides, lattice defects, hydrogen solution strengthening and Al element diffusion jointly cause the hardness of beta phase increase with the increasing hydrogen.

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Low-temperature diffusion bonding of Ti6Al4V alloy via nanocrystallization and hydrogenation surface treatment

Wenqi Zhao, Chun Li, Tong Lin, Jianwei Gao, Xiaoqing Si, Junlei Qi, Xiangyu Dai, Jian Cao

Summary: Hydrogenation and nanocrystallization of Ti6Al4V alloy were achieved through electrolytic hydrogenation and SMAT processing. The hydride d phase was observed after 4 hours of hydrogenation, while the grain size of Ti6Al4V alloy reached below 35 nm after 2 hours of SMAT processing. The surface morphology and roughness were characterized by AFM. Diffusion bonding of Ti6Al4V alloys at low temperature was successfully achieved under different parameters. The porosity at the interface decreased with increasing hydrogenation or nanocrystallization time. When the hydrogenation time reached 24 hours or the nanocrystallization time reached 4 hours, the porosity of the joint reached 0. The combination of hydrogenation and nanocrystallization treatments resulted in more bonding defects compared to joints treated with single hydrogenation or nanocrystallization. It was concluded that joints with nanocrystallization as the first treatment had lower porosity compared to joints with hydrogenation as the first treatment.

JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T (2023)