| 研究課題/領域番号 |
20F40737
|
|---|
| 研究機関 | 九州大学 |
|---|
研究代表者 |
陳 強 九州大学, 工学研究院, 教授 (30264451)
|
|---|
| 研究分担者 |
LIU HANQING 九州大学, 工学(系)研究科(研究院), 外国人特別研究員
|
|---|
| 研究期間 (年度) |
2020-11-13 – 2023-03-31
|
| キーワード | Titanium alloy / Phase transformation / Slip deformation / Crack nucleation |
|---|
| 研究実績の概要 |
Metastable microstructures in titanium alloy joints could be formed during the solidification process because of the high cooling rate, resulting in a heterogeneous mechanical response to the tensile and fatigue loading. The topmost layer exhibits the best plasticity properties due to the martensite transformation behavior, on contrary, the metastable thermal martensite formed during solidification could damage the ductility of the weld joint. Such microstructural heterogeneities could therefore facilitate the discrepancy in fatigue crack nucleation behavior. The formation of thermal martensite could facilitate the crack nucleating from the matrix grain boundary, while slip deformation could be actived within the thermal martensite free grains, resulting in fatigue crack nucleation. Such microstructural deficiencies could be reduced by the following direct aging treatment with optimized parameters, and therefore enhance the mechanical properties of the materials.
|
| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
Generally, we have accomplished the planned research. Further research on the deformation behavior of precipitates during fatigue crack nucleation and the microstructural mechanisms on the crack extension activities will be carried out. The relatated mechanical tests are under conducted and the obtained results meet our expectations.
|
| 今後の研究の推進方策 |
1. Crack extension mechanism will be carried out by site specifically introducing micro defects into the regions with target microstructures to study the influence of twin boundary and Schmidt factor (SF) on cyclic deformation precess using EBSD. A quantitative analysis will be carried out to investigate the crack propagation rate before the Paris domain.
2. The influences of precipitates on the will be carried out by controlling the holding time of aging treatment and therefore modifying the size and volume fraction of the material. The interaction of dislocation with the interface of precipitates and matrix, as well as the evolution of solution atoms neighboring to the dislocation will furtherly be characterized using AC-STEM.
|
