| Project/Area Number |
10450256
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Structural/Functional materials
|
|---|
| Research Institution | Tokyo Institute of Technology |
|---|
Principal Investigator |
WAKASHIMA Kenji Precision and Intelligence Laboratory, Tokyo Institute of Technology, Professor, 精密工学研究所, 教授 (70016799)
|
|---|
| Project Period (FY) |
1998 – 1999
|
| Project Status |
Completed (Fiscal Year 1999)
|
| Budget Amount *help |
¥9,600,000 (Direct Cost: ¥9,600,000)
Fiscal Year 1999: ¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1998: ¥7,100,000 (Direct Cost: ¥7,100,000)
|
|---|
| Keywords | Composite Materials / Creep / Stress Relaxation / Interfacial Diffusion / Viscous Sliding / Micromechanics / Internal Stress / Metal Matrix Composites / 界面すべり / 金属基複合材料 |
|---|
| Research Abstract |
Theoretical and experimental work has been done in this project with a primary objective to indicate a new route to the understanding of high-temperature deformation behavior (creep) of metal-matrix composites (MMCs) with ceramic reinforcements--a class of light-weight high-stiffness 'advanced materials' currently ranked above conventional metallic materials especially for use in elevated temperature environment. Emphasis is placed on the viscous nature of metal-ceramic phase interfaces which causes 'stress relaxation' and hence plays a substantial role in creep of MMCs. First, as basic preliminaries to our intention, a series of analysis based on 2-D and 3-D continuum models has been made to formulate a micromechanical description of creep in two-phase (or multi-phase) solid systems wherein both diffusional mass flow and viscous sliding occur along phase interfaces. This description is applied to diffusional creep in polycrystals, leading us to make comments on existing theories where
… More
in the role of boundary sliding is entirely ignored. It is found that such theories can be justified only if boundary viscosity is so small that sliding can occur instantaneously. Further effort is devoted exclusively to our primary objective, giving special attention to particulate SiC-reinforced aluminum-based MMCs produced by powder-metallurgy processing routes. To begin with, 'anelastic relaxation' caused by diffusional creep around ceramic particulates is addressed. A micromechanical model of the relaxation has been presented and its validity confirmed from measurements of dynamic Young's modulus and internal friction, each as a function of temperature, in low-amplitude low-frequency conditions of cyclic uniaxial loading. The model is then extended into the high-stress 'dislocation creep' regime for the matrix, i.e. the case where the matrix itself does not remain elastic but creeps according to the 'power law.' With attention confined to the 'class I creep behavior' characterized by the particular stress exponent n = 3, nonlinear unsteady creep behavior of MMCs has been formulated in an entirely analytical manner. This formulation allows us to gain new insight into a 'puzzle' as to the anomalously high apparent stress exponents in 'minimum creep rate' data for MMCs. The crux of the matter consists in that damage processes (particle cracking and interface debonding) very likely occur in creep at high stresses and hence not all the minimum creep rate data should be interpreted as representatives of the steady state. This has been substantiated by carefully designed experiments on a particulate SIC/6061 A1 MMC. Less
|
