Introduction
Experimental
Material and Methods
Element | Ti | Al | V | Fe | Cr | Cu | O | N | C | H |
---|---|---|---|---|---|---|---|---|---|---|
wt.% | 89.36 | 6.4 | 3.96 | 0.07 | 0.01 | 0.01 | 0.119 | 0.024 | 0.015 | 61 ppm |
Hardness Testing and Microstructural Characterization
Results and Discussion
Before Post-Heat Treatment
Stress-Relief Followed by Post-Heat Treatment
Solution temperature | 930 °C | 1015 °C | ||||
---|---|---|---|---|---|---|
Cooling | WQ | AC | FC | WQ | AC | FC |
Hardness (HV0.3) | 336 ± 6 | 330 ± 4 | 327 ± 6 | 391 ± 7 | 382 ± 3 | 356 ± 1 |
Phase | α′ + α | α + 7.5% β | α + 17% β | α′ | α + very low content of β | α + 8.5% β |
Stress-Relief and HIP Followed by Post-Heat Treatment
Conclusion
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The microstructural examination of the stress-relieved samples followed by solution treatment at 930 °C indicated that the quenched samples were characterized by a mixture of α and large needles of α′ phase. Air cooling produced a structure dominated by the α phase, with a small amount of the β phase being observed. Furnace cooling from 930 °C exhibited a microstructure with a coarse plate-like mixture of α phase and ~17% of the β phase with no α′ martensite phase being noted.
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The stress-relieved and HIPed specimens demonstrated coarse grains composed of a lamellar α + 6% β microstructure.
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The stress-relieved and HIPed specimens exposed to post-heat treatment at 930 °C followed by quenching exhibited a microstructure of needle-like martensite microstructure, and αGB was observed. After air cooling, the β-phase transformed to the α-phase leading to a mixture of α + β phase and some needles of α' phase left in their microstructures. After furnace cooling, a complete transformation of β to α + β mixture was observed, and the pattern of α lath was formed.
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The solution-treated and water-quenched samples with the HIP processing have a higher hardness value comparing to those without the HIP, due to grain size effect and the reduced porosity.