Ultra-fine Equiaxed Grain Refinement and Improvement of Mechanical Properties of &amp;alpha;+&amp;beta; Type Titanium Alloys by Hydrogenation, Hot Working, Heat Treatment and Dehydrogenation

Yoshimura, Hirofumi; Kimura, Kazuo; Hayashi, Masayuki; Ishii, Mitsuo; Hanamura, Toshihiro; Takamura, Jin-ichi

doi:10.2320/matertrans1989.35.266

Cited by 34 publications

(19 citation statements)

References 5 publications

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“…Generally, in presence of hydrogen, the grain re nement in titanium alloys may be attributed to the three factors; (i) The nely distributed titanium hydride precipitates act as dislocation pile-up points, and thus became ideal sites for the formation of recrystallization nuclei (ii) hydrogen stabilize the beta phase and thus lowered the beta transus temperature and resulted in lowering in hot working conditions to retain the dislocation cell structures formed during the deformation and (iii) during fast cooling from beta phase region, uniformly distributed high-density dislocations are introduced in acicular martensites. A combination of these factors results in grain re nement of such hydrogenated titanium alloys 33) . Therefore, the formation of ne particles as well as less compositional variations for long time mechanically milled (180 ks) powder gives rise to the higher degree of homogeneity in the specimen-B.…”

Section: Phases and Microstructures Of Sintered Compactsmentioning

confidence: 99%

Synthesis of Ternary Ti-25Nb-11Sn Alloy by Powder Metallurgy Route Using Titanium Hydride Powder

2016

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In the present work, Ti-25Nb-11Sn (mass%) alloys were successfully prepared by an advanced powder metallurgy method. The alloys were synthesized by mechanical milling of powder mixture, consisting of titanium hydride (TiH 2 ), elemental niobium (Nb) and elemental tin (Sn) powders, followed by their consolidation via Spark Plasma Sintering (SPS) method. The use of brittle TiH 2 powder, instead of ductile elemental Ti powder, resulted in ~100% powder yield of mechanically milled (MMed) powder even after long time mechanical milling. The resulting MMed powders consisted of homogeneously distributed nano-sized titanium/niobium hydride powder particles together with a few micron-sized pure Nb particles. The mechanical milling also led to the lowering of dehydrogenation temperature of the hydride particles. Sintering of short time mechanically milled powder (72 ks) resulted in the ne-grained heterogeneous microstructure consisting of β phase and orthorhombic martensitic α phase. On the other hand, sintering of long time mechanically milled powder (180 ks) resulted in the evolution of β-phase and α-phase. The specimen containing α+β phase exhibited higher average hardness as compared to the average hardness of specimen containing α +β phase.

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Section: Phases and Microstructures Of Sintered Compactsmentioning

confidence: 99%

Synthesis of Ternary Ti-25Nb-11Sn Alloy by Powder Metallurgy Route Using Titanium Hydride Powder

2016

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“…Hydrogenation treatment was commonly employed to obtain fine equiaxed grain structures in = Ti-alloys. 9,10,15) The VHP/LPPS Ti-Al-V contained randomly distributed Widmanstätten inclusion consisting of acicular -phase with laths of -phase between the , as indicated by circles in Fig. 3(b).…”

Section: Plasma Sprayed Microstructurementioning

confidence: 99%

Microstructural Evolution and Tensile Properties of Ti-Al-V Alloys Manufactured by Plasma Spraying and Subsequent Vacuum Hot Pressing

Baik

2006

Mater. Trans.

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Ti-Al-V preforms were manufactured by low pressure plasma spraying (LPPS) from two different sizes of Ti-6Al-4V feedstock powders, and subsequently consolidated by vacuum hot pressing (VHP). During LPPS, a loss of alloying elements and an incorporation of [H] and [O] occurred, which were much significant for a smaller feedstock powder. Subsequent VHP completely removed [H] content, whereas a considerable amount of [O] remained. The microstructure of LPPS deposits comprised a splat-quenched lamellar structure, incorporating unmelted particles. The each splat contained 0 martensite plates and Ti hydrides which provided heterogeneous nucleation sites for recrystallization during subsequent VHP, transforming into an equiaxed grain structure. The tensile properties of LPPS/VHP Ti-Al-V alloy were primarily affected by [O] content. An increase in [O] content up to 0.35 mass% increased tensile strength, but dramatically decreased ductility. Further [O] incorporation formed a large fraction of embrittled -phase, resulting in a significant decrease in both tensile strength and ductility.

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“…The equiaxed microstructures were mainly attributed to Ti-hydrides in the LPPS splat, which provided a large number of heterogeneous nucleation sites for recrystallization during VHP. Hydrogenation treatment has been commonly employed to obtain fine equiaxed grain structures in α/β Ti-alloys [20]. The VHP consolidated material had a very low [H] content, as shown in Table 2, because of the instability of Ti-hydrides and the high diffusion rate of [H] in Ti at elevated temperature in vacuum [18].…”

Section: Fiber Distribution and Void Forma-tionmentioning

confidence: 99%

Processing and properties of metallic and ceramic matrix composites by a novel spraying technique

Baik

2004

Met. Mater. Int.

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A concurrent fiber winding and low pressure plasma spraying process has been developed to manufacture multi-ply fiber reinforced metallic and ceramic matrix composites in a single spraying operation. In this study, four-layer SiC fiber reinforced Ti-6Al-4V and SiAlON-MoSi 2 composites have been manufactured, and the composite coupons have been evaluated in terms of fiber breakage, fiber distribution, matrix microstructure, interfacial reaction, and fiber damage. This novel spraying route enabled a wide range of composite systems to be produced, offering rapidly solidified matrix microstructure, regular fiber spacing and minimized interfacial reaction. Fiber damage was considered as a potential major disadvantage, but compared with the more widely investigated foil-fiber-foil route, this novel spraying approach resulted in less degradation in fiber strength. Further minimization of fiber damage could be achieved by precise control over processing conditions and large damage tolerance of fiber coating.

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Ultra-fine Equiaxed Grain Refinement and Improvement of Mechanical Properties of α+β Type Titanium Alloys by Hydrogenation, Hot Working, Heat Treatment and Dehydrogenation

Cited by 34 publications

References 5 publications

Synthesis of Ternary Ti-25Nb-11Sn Alloy by Powder Metallurgy Route Using Titanium Hydride Powder

Synthesis of Ternary Ti-25Nb-11Sn Alloy by Powder Metallurgy Route Using Titanium Hydride Powder

Microstructural Evolution and Tensile Properties of Ti-Al-V Alloys Manufactured by Plasma Spraying and Subsequent Vacuum Hot Pressing

Processing and properties of metallic and ceramic matrix composites by a novel spraying technique

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