Laser Additive Manufacturing (LAM) was employed to fabricate repaired specimens with wrought TC4 as the substrate and TC4 powders with low oxygen (O≤0.13wt%) as the cladding materials. The microstructure and mechanical properties of TC4 specimens fabricated by LAM and wrought billet were investigated comparatively. The results show that the macrostructure of the laser repaired specimen can be divided into three domains, including wrought substrate zone (SZ), heat affected zone (HAZ) and laser deposited zone (LDZ). The LDZ microhardness is equal to that of the SZ basically. And the HAZ microhardness is higher than that of both the LDZ and SZ slightly. The results of room temperature tensile test show that the strength and ductility of the wrought specimen are slightly higher than that of the laser repaired specimens. Meanwhile, the strength of the laser repaired specimen with repair ratio of 40% (i.e. area fraction of the LDZ on the transverse section of tensile specimen within gauge part is 40%)is slightly lower than that of 50% repaired specimen, but the ductility is higher than the latter. Therefore it is favorable to match the strength and ductility of the wrought substrate with the LDZ with low oxygen TC4 powders as the cladding materials, so as to improve the comprehensive properties of laser repaired TC4 titanium alloy. The wrought specimen tensile fracture presents a typical ductile characteristic, and the repaired specimen shows a complex fractograph. From the LDZ to the SZ, the tensile fracture presents a successive transformation from cleavage step to dimple fracture. It can be seen that there is a good corresponding relationship between the fracture morphology and the microstructure of the tensile specimens.
Fatigue analysis of Jet engine structures require the definition of a load spectrum representative of the ln-servlce structural loads environment. This paper presents a technique for generating programmed step loads designed to predict the life of blading vibration from sampling measured 100-hr flight blading vibration load data produced by simulation. Under the resulting loads, a fatigue test for TC4 titanium alloy blading has been carried out with a computer-controlled servo-electrical rig. In contrast with previous constant-load test where life can be predicted at an assumed stress, the life here Is estimated for a randomly vibrating stress which produces more meaningful and reliable results. A P-S-N curve for the blading is obtained experimentally under system control using an Apple-II. Large amounts of blade vibration random load spectrum from typical fighter Jet on a variety of missions is treated statistically and converted Into block load program by newly processed counting software using computer and interfaces. Both the derivation for load spectrum simulation and the results of fatigue performance of TC4 are discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.