| Summary: | 碩士 === 國立臺灣海洋大學 === 材料工程研究所 === 98 === In this study, the influence of post-weld heat treatments (PWHTs) on the mechanical properties and microstructures of Ti-15V-3Cr-3Sn-3Al (Ti-15-3) laser welds, which were aged in the temperature range of 317 to 593 oC, were determined. Moreover, the mechanical properties of the welds were compared with the un-welded base plate in the same aging condition.
The ultimate tensile strength of the aged plate varied in the same manner as the hardness, but inversely with ductility. The specimens aged at 371 oC (under-aged specimen) were the most susceptible to notch brittleness among the specimens being tested, regardless of aged plate or weld. An obvious rise in notched tensile strength (NTS) was obtained for the specimens aged at 538 oC or higher. The fracture toughness of the plate was consistent with its NTS, i.e., higher fracture toughness corresponding to greater NTS. The as-welded weld possessed the highest impact toughness in all specimens. However, aging treatment at 371 oC caused an abrupt drop in weld’s ability to resist unstable crack growth. Besides, the welds aged at/above 371 oC had lower impact toughness than the un-weld plate aged at the same temperature. The results of fatigue crack growth tests showed the un-welded specimen aged at 371 oC had a slightly higher fatigue crack growth rate than the other aged specimens
|
|---|
