Application of Precipitate Free Zone Growth Kinetics to the β-Phase Depletion Behavior in a CoNiCrAlY Coating Alloy: An Analytical Approach

There is a widespread interest in understanding the properties of Al-base alloys so that progress can be made toward extending their present applications in the aircraft industry. Al-Zn-Mg is precipitation hardened to gain its high strength; however, during aging the formation of heterogeneous precipitates on the grain boundaries creates a precipitate-free zone in the adjacent region. Since high angle grain boundaries are not easily characterized, it is difficult to establish a relationship between the precipitate and the boundary structure. Therefore, this study involves precipitation on low angle grain boundaries where the boundary and the precipitate can be fully analyzed.

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Quench sensitivity of toughness in an Al alloy: Direct observation and analysis of failure initiation at the precipitate-free zone

Acta Materialia ◽

10.1016/j.actamat.2008.02.021 ◽

2008 ◽

Vol 56 (12) ◽

pp. 2872-2884 ◽

Cited By ~ 53

Author(s):

T.F. Morgeneyer ◽

M.J. Starink ◽

S.C. Wang ◽

I. Sinclair

Keyword(s):

Direct Observation ◽

Al Alloy ◽

Precipitate Free Zone ◽

Quench Sensitivity ◽

Failure Initiation ◽

Free Zone

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Effect of Strain Amounts on Cold Compression Deformation Mechanism of Ti-55531 Alloy with Bimodal Microstructure

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1035.182 ◽

2021 ◽

Vol 1035 ◽

pp. 182-188

Author(s):

Jian Hua Cai ◽

She Wei Xin ◽

Lei Li ◽

Lei Zou ◽

Hai Ying Yang ◽

...

Keyword(s):

Plastic Deformation ◽

Deformation Mechanism ◽

True Strain ◽

Bimodal Microstructure ◽

Free Zone ◽

Β Phase ◽

Α Phase ◽

Initial Stage ◽

Pile Up ◽

Dislocation Tangle

The plastic deformation mechanism of Ti-55531 alloy with bimodal microstructure was investigated by compression testing at room temperature. The bimodal microstructure was composed of equiaxed primary α phase (αp) and transformed β (βtrans) that consisted of acicular secondary α phase (αs) and residual β phase (βr). In the initial stage of deformation, the αp grains first underwent plastic deformation, the dislocations germinated and increased, forming the dislocation loop with the dislocation free zone in αp at the true stain of 0.083. With the true strain subsequently increasing to 0.105, the dislocation tangle and dislocation pile-up occurred in αp, and a lot of dislocations were also activated in most of αs. Moreover, the dislocation density was increasing gradually in βr with the adding of strain. Finally, the dislocation pile-up and dislocation tangle appeared in αs and βr at the true strain of 0.163. The whole deformation process was coordinated by αp, αs and βr. They accommodated mutually and completed deformation together.

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A MEAN FIELD DESCRIPTION OF THE KINETICS OF PRECIPITATE FREE ZONE FORMATION

Scripta Materialia ◽

10.1016/s1359-6462(97)00369-2 ◽

1997 ◽

Vol 37 (12) ◽

pp. 2033-2039 ◽

Cited By ~ 2

Author(s):

J.J. Hoyt

Keyword(s):

Mean Field ◽

Precipitate Free Zone ◽

Zone Formation ◽

Free Zone ◽

Kinetics Of

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Formation of Large Size Precipitate-Free Zones in β Annealing of the Near-β Ti-55531 Titanium Alloy

Metals ◽

10.3390/met9050544 ◽

2019 ◽

Vol 9 (5) ◽

pp. 544 ◽

Cited By ~ 3

Author(s):

Xueqi Jiang ◽

Xiaoqiang Shi ◽

Xiaoguang Fan ◽

Qi Li

Keyword(s):

Titanium Alloy ◽

Phase Transformation ◽

Heterogeneous Nucleation ◽

Isothermal Heat Treatment ◽

Precipitate Free Zone ◽

Mode Iii ◽

Slow Cooling ◽

Free Zone ◽

Large Size ◽

Α Phase

Large size (>10000 μm2) precipitate-free zones in the absence of microsegregation were observed in the near-β Ti-55531 titanium alloy after furnace cooling from high temperature and longtime annealing in the single-β phase field. To reveal the formation mechanism of the large size precipitate-free zone, continuous cooling and isothermal heat treatment were carried out to investigate the β-α phase transformation process. It was found that the large size precipitate free zone is attributed to the heterogeneous nucleation of α phase. The nucleation site evolves in three different modes: I-random nucleation inside the β grain, II-network nucleation inside the β grain and, III-heterogeneous nucleation on the precipitated α phase. Modes I and II lead to homogeneous transformed structure while Mode III results in the large size precipitate-free zone. Both modes II and III are promoted at high annealing temperature, rapid cooling above 600 °C or slow cooling below 600 °C. Mode II is common as it can minimize the strain energy in phase transformation. As a result, the formation of the large size precipitate-free zone is not deterministic.

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