Swelling during liquid phase sintering of Ti–Ni alloys

Robertson, I. M.; Schaffer, G. B.

doi:10.1179/174329009x380590

Cited by 18 publications

(26 citation statements)

References 36 publications

(47 reference statements)

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“…Ti-Ni-Sn PM systems [12,[22][23][24][25], although a slightly higher compaction pressure of 400 MPa was used in those studies, along with more coarse initial elemental powder sizes. The addition of Sn improves the green density when higher contents are used (i.e.…”

Section: Powder Compaction Behaviourmentioning

confidence: 99%

A comparison of Ti–Ni and Ti-Sn binary alloys processed using powder metallurgy

Liu

Bishop

Plucknett

2015

Materials Science and Engineering: A

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Section: Powder Compaction Behaviourmentioning

confidence: 99%

A comparison of Ti–Ni and Ti-Sn binary alloys processed using powder metallurgy

Liu

Bishop

Plucknett

2015

Materials Science and Engineering: A

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“…Swelling is usually attributable to the formation of gas in closed pores. [25] However, these compacts are somewhat irregular in shape. As indicated in Section II, irregular shape results in the geometric density value being slightly lower than Archimedes' density.…”

Section: Sumitomo-100 Mesh Ti Powdermentioning

confidence: 98%

Refinement of Master Densification Curves for Sintering of Titanium

Robertson

Schaffer

2010

Metall Mater Trans A

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An approximate master curve for the densification of cold-pressed titanium powder during vacuum sintering was published previously. It was based on the combined results for three different titanium powders. The master densification curve model incorporates the effects of particle size, compaction pressure, sintering time, and sintering temperature on densification. The collection of a large amount of additional data now allows refinement of the model. Distinct curves are presented for three different titanium powders, prealloyed Ti6Al4V, and Ti-Ni binary alloys. The master densification curve is sigmoidal, but deviates from the ideal form at high sintered density; the relative sintered density saturates at 90 to 100 pct, depending on the particle size of the titanium powder, and to a lesser extent the compaction pressure. The master densification curve below the saturation level is slightly dependent on the compaction pressure.

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“…The small discrepancy (~0.7 percentage points) may be due to slight uncertainty in the theoretical density of the Ti-5Si alloy. Ti-Ni alloys [22] during liquid phase sintering also demonstrate a dramatic increase in sintered density with a trace addition of Y 2 O 3 . At 1573 K (1300°C), the Ti6Ni and Ti-7Ni alloy form approximately 2 wt pct and 10 wt pct liquid, respectively.…”

Section: B Liquid Phase Sinteringmentioning

confidence: 99%

“…Mitigation techniques such as degassing of powders prior to sintering have very limited efficacy. [16,22,24] High-purity powders can be used to avoid these problems, [4,11,17,25] but since they are often derived from conventional ingot metallurgy, any potential savings associated with PM are lost.…”

Section: Introductionmentioning

confidence: 99%

“…[4,12,17] The effects of chlorides on sintering are most significant in the presence of liquid. [21][22][23] For example, chloride volatilization during liquid phase sintering leads to the formation of very large pores (sometimes millimeters in size) that are few in number. [21,23] Chlorine concentrations greater than 50 ppm are reported to cause severe sputtering and a highly porous weld zone during fusion welding.…”

Section: Introductionmentioning

confidence: 99%

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Sintering of Titanium with Yttrium Oxide Additions for the Scavenging of Chlorine Impurities

Löw

Qian

Schaffer

2012

Metall Mater Trans A

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Chloride impurities in titanium powders are extremely difficult to remove and present a longstanding problem in titanium powder metallurgy. We show that the detrimental effects of chlorides on the sintering of titanium can be mitigated with trace additions of yttrium oxide, which has a high affinity for the normally volatile species and forms highly stable oxychloride reaction products. Compacts that would otherwise exhibit gross swelling and excessive porosity due to chloride impurities can be now sintered to near full density by liquid phase sintering. The potency of yttrium oxide additions is observable at levels as low as 500 ppm. The scavenging of chlorine by Y 2 O 3 appears to be independent of alloy composition and sintering regime. It is effective when used with high-chloride powders such as Kroll sponge fines but ineffective when used with powders containing NaCl impurities or during solid-state sintering. The identification of highly potent chlorine scavengers may enable the future development of chloride-tolerant powder metallurgy (PM) alloys aimed at utilizing low-cost, high-chloride powder feedstocks.

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Swelling during liquid phase sintering of Ti–Ni alloys

Cited by 18 publications

References 36 publications

A comparison of Ti–Ni and Ti-Sn binary alloys processed using powder metallurgy

A comparison of Ti–Ni and Ti-Sn binary alloys processed using powder metallurgy

Refinement of Master Densification Curves for Sintering of Titanium

Sintering of Titanium with Yttrium Oxide Additions for the Scavenging of Chlorine Impurities

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