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Nagano-shi, Japan

Takizawa Y.,Kyushu University | Takizawa Y.,Nagano Forging Co. | Otsuka K.,Kyushu University | Masuda T.,Kyushu University | And 4 more authors.
Materials Science and Engineering A | Year: 2015

A Ni-based superalloy (Inconel 718) was successfully processed by high-pressure torsion (HPT) under a pressure up to 6GPa at room temperature. The grain size after the HPT processing was reduced to ~100nm. Tensile testing at 1073K led to the advent of superplasticity with a maximum elongation of 1190% at a strain rate of 2×10-2s-1 which is well in the range of high-strain-rate superplasticity. This superplastic flow was accompanied by a significant decrease in the flow stress. © 2015 Elsevier B.V.

Takizawa Y.,Kyushu University | Takizawa Y.,Nagano Forging Co. | Masuda T.,Kyushu University | Fujimitsu K.,Kyushu University | And 5 more authors.
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2016

The process of high-pressure sliding (HPS) is a method of severe plastic deformation developed recently for grain refinement of metallic materials under high pressure. The sample for HPS is used with a form of sheet or rod. In this study, an HPS facility with capacities of 500 tonnes for vertical pressing and of 500 and 300 tonnes for horizontal forward and backward pressings, respectively, was newly built and applied for grain refinement of a Mg alloy as AZ61, Al alloys such as Al-Mg-Sc, A2024 and A7075 alloys, a Ti alloy as ASTM-F1295, and a Ni-based superalloy as Inconel 718. Sheet samples with dimensions of 10 to 30 mm width, 100 mm length, and 1 mm thickness were processed at room temperature and ultrafine grains with sizes of ~200 to 300 nm were successfully produced in the alloys. Tensile testing at elevated temperatures confirmed the advent of superplasticity with total elongations of more than 400 pct in all the alloys. It is demonstrated that the HPS can make all the alloys superplastic through processing at room temperature with a form of rectangular sheets. © 2016, The Minerals, Metals & Materials Society and ASM International.

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