1999 Fiscal Year Final Research Report Summary
Microstructure control and ultra-high strengthening of stainless steel by the room temperature recrystallization
| Project/Area Number |
10450263
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Structural/Functional materials
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| Research Institution | Ritsumeikan University |
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Principal Investigator |
AMEYAMA Kei Ritsumeikan University, Fac.Science and Engineering, Professor, 理工学部, 教授 (10184243)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAME Masao Ritsumeikan University, Fac.Science and Engineering, Professor, 理工学部, 教授 (20111130)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Powder Metallurgy / Stainless Steel / HS-PM Process / Reemystallization / Hachanical Property / Strength / Microstructure / Grain Refinement |
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| Research Abstract |
The high strain powder metallurgy (HS-PM) process is a novel powder metallurgy process combining mechanical milling (MM) or mechanical alloying (MA), heat treatment and sintering processes, and enables one to produce an ultra-fine grain structure. It has three remarkable features : [1] a non equilibrium phase, [2] a nano grain microstructure, and [3] good workability. The extremely high strain energy given by the milling process at room temperature produces a large number of defects and this enhances the diffusion of atoms at low temperature and contributes to the formation of a non equilibrium phase such as a supersaturated solid solution or an amorphous phase. A nano grain structure is obtained from the non-equilibrium phases by controlling the heat treatment conditions, which influences the phase transformation, recovery, recrystallization, grain growth, etc (2). Grain refinement is very important to improve the mechanical properties of materials, and fine grained materials easily deform by superplasticity. Therefore, the HS-PM process is the most efficient and useful non-equilibrium powder metallurgy process because it permits simultaneous improvement of mechanical properties and workability by the control of microstructure.
In this report, the HS-PM process was applied to an SUS316L stainless steel, and the mechanical properties of the material at room temperature as well as the microstructural changes during the process are discussed. The HIP compact of the HS-PM processed powder showed ultra-fine microstructure with a homogeneously dispersed σphase. The HIP compact also showed outstanding mechanical properties at room temperature as well as at the elevated temperatures.
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