A critical evaluation of the microstructural gradient along the build direction in electron beam melted Ti-6Al-4V alloy
| Autor: | David Parfitt, Emmanuel Muzangaza, Hitesh Sharma, D. I. Wimpenny, Gavin J. Baxter, Bo Chen, Abdul Khadar Syed |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
010302 applied physics
Mechanical property Materials science Mechanical Engineering chemistry.chemical_element 02 engineering and technology Lath engineering.material 021001 nanoscience & nanotechnology Condensed Matter Physics Microstructure 01 natural sciences Temperature gradient Cooling rate chemistry Mechanics of Materials 0103 physical sciences engineering Cathode ray General Materials Science Ti 6al 4v Composite material 0210 nano-technology Titanium |
| Zdroj: | Materials Science and Engineering: A. 744:182-194 |
| ISSN: | 0921-5093 |
| DOI: | 10.1016/j.msea.2018.12.016 |
| Popis: | It is generally recognised that electron beam melted (EBM) Ti-6Al-4V alloys exhibit a microstructural gradient along the build direction, but there have been some inconsistent experimental observations and debate as to the origin and magnitude of this effect. Here we present an unambiguous evaluation of this microstructural gradient and associated mechanical property along the EBM build direction on purpose-built round bar RB samples with build height of 380 mm and rectangular plate RP samples with build height of 120 mm. Columnar prior β grain width was found to increase (from 86 ± 38 to 154 ± 56 µm in RB and from 79 ± 34 to 122 ± 56 µm in RP samples) with the build height and the similar increase was also observed for α lath width (from 0.58 ± 24 to 0.87 ± 33 µm in RB and from 1.50 ± 45 to 1.80 ± 49 µm in RP samples). These observations can be attributed to the thermal gradient in the powder bed that produced a cooling rate gradient along the build height. The measured α lath width variation along the build height followed a log-normal distribution. The graded microstructure resulted in a decrease in micro-hardness which correlated very well with the mean α lath width by following a Hall-Petch relation. |
| Databáze: | OpenAIRE |
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