Speaker
Description
Technological enhancements created new demands on the material properties of aerospace materials. One of the most common materials used in the aerospace industry is titanium alloys because of their high strength to volume ratio. To meet these needs, titanium alloys with higher operating temperatures and with better mechanical properties are developed. Titanium alloys consist of alpha and beta phases and the enhanced properties are provided with a higher amount of alpha phase in titanium alloy, which is called near-alpha alloys. The high amount of alpha phase increases the maximum operating temperature and increases the mechanical properties of titanium alloys.The alpha phase has an HCP (Hexagonal Close Packed) and the beta phase has a BCC (Body-Centered Cubic) structure, which causes anisotropic behavior. Because of this behavior, when the material is subjected to low temperature and moderate stress, material suffers from a unique phenomenon that is called “Cold Dwell Fatigue”. Applied stress is redistributed inside of the material due to the anisotropic behavior and strain accumulation takes place because of the dwell period. Both stress redistribution and strain accumulation fail the material. This characteristic failure shows a combination of ductile and brittle fracture mechanisms. Cold Dwell phenomena have a distinctive fracture surface with displaying “quasi-cleavage facet”. In this research, Cold Dwell Fatigue sensitivity of Ti-6Al-2Sn-4Mo-2Zr (Ti-6242) near-alpha alloy is investigated. To have a better understanding of the effect of temperature and dwell time on the “Cold Dwell Fatigue” phenomena of near-alpha alloys, fatigue tests have been performed. These tests take place under two different temperatures and three different dwell periods that are considered to be the susceptible conditions for the Cold Dwell Fatigue sensitivity of near-alpha alloys. Relations between the mechanical test results and microstructural examinations are examined in detail.
| Speaker Country | Turkey |
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