Effects of B and W alloying additions on the formation and stability of lamellar structures in two-phase γ-TiAl

P. J. Maziasz; R. V. Ramanujan; C. T. Liu; J. L. Wright

doi:10.1016/S0966-9795(96)00070-2

Effects of B and W alloying additions on the formation and stability of lamellar structures in two-phase γ-TiAl

P. J. Maziasz^*, R. V. Ramanujan, C. T. Liu, J. L. Wright

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

83 Citations (Scopus)

Abstract

The effects of additions of 140 appm B and 0.5 at.% W on the formation and stability of fully-lamellar structures in a Ti-47Al base alloy were studied. The fully-lamellar structure was formed by heat-treatment at 1400°C for 1 h (in vacuum) followed by furnace cooling. Stability was studied by aging these alloys for 168 h at 800, 1000 and 1200°C and making quantitative measurements of lamellar structure parameters (i.e. average lamellar spacing, α₂-α₂ spacing) using transmission electron microscopy (TEM) and hardness measurements. The B addition alone refines the lamellar structure relative to the binary TiAl alloy, but causes fragmented and discontinuous α₂ lamellae. By contrast, W+B addition refines the lamellar structure and produces more uniform and continuous α₂ lamellae. The as-heat-treated Ti-47Al+W+B alloy is harder than the other two alloys. Aging for 168 h at 800°C does not change the fine initial lamellar microstructure of any of these alloys. Aging at 1000°C significantly coarsens the Ti-47Al alloy, causes some coarsening in the Ti47Al+B alloy, but has little effect on the lamellar structure of the Ti-47Al+W+B alloy. Aging at 1200°C causes discontinuous coarsening and complete loss of the initial, fine, lamellar microstructure in all three alloys. Aging in vacuum produces a subsurface 'damage region' consisting of an α(Ti₃Al) surface layer with another layer of coarsened γ microstructure underneath. At 1000°C, this layer is greatest in the binary alloy and least in the Ti-47Al+W+B alloy. Specimens were 5.5% cold-forged and then aged at 1000°C to evaluate the effects of subsurface deformation caused during cutting of the specimens. Prior cold-deformation caused considerable recrystallization in the binary alloy, but almost none in the Ti-47Al+W+B alloy. The additions of W and B to a Ti-47Al alloy refine the fully-lamellar structure obtained by heat-treatment, and make it more resistant to lamellar coarsening (and recrystallization if cold deformed) during aging at 800-1000°C.

Original language	English
Pages (from-to)	83-95
Number of pages	13
Journal	Intermetallics
Volume	5
Issue number	2
DOIs	https://doi.org/10.1016/S0966-9795(96)00070-2
Publication status	Published - 1997
Externally published	Yes

ASJC Scopus Subject Areas

General Chemistry
Mechanics of Materials
Mechanical Engineering
Metals and Alloys
Materials Chemistry

Keywords

A. titanium aluminides (based on TiAl)
B. microalloying
D. microstructure

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10.1016/S0966-9795(96)00070-2

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@article{15eb6714329d4d2daeb9c432badb1201,

title = "Effects of B and W alloying additions on the formation and stability of lamellar structures in two-phase γ-TiAl",

abstract = "The effects of additions of 140 appm B and 0.5 at.% W on the formation and stability of fully-lamellar structures in a Ti-47Al base alloy were studied. The fully-lamellar structure was formed by heat-treatment at 1400°C for 1 h (in vacuum) followed by furnace cooling. Stability was studied by aging these alloys for 168 h at 800, 1000 and 1200°C and making quantitative measurements of lamellar structure parameters (i.e. average lamellar spacing, α2-α2 spacing) using transmission electron microscopy (TEM) and hardness measurements. The B addition alone refines the lamellar structure relative to the binary TiAl alloy, but causes fragmented and discontinuous α2 lamellae. By contrast, W+B addition refines the lamellar structure and produces more uniform and continuous α2 lamellae. The as-heat-treated Ti-47Al+W+B alloy is harder than the other two alloys. Aging for 168 h at 800°C does not change the fine initial lamellar microstructure of any of these alloys. Aging at 1000°C significantly coarsens the Ti-47Al alloy, causes some coarsening in the Ti47Al+B alloy, but has little effect on the lamellar structure of the Ti-47Al+W+B alloy. Aging at 1200°C causes discontinuous coarsening and complete loss of the initial, fine, lamellar microstructure in all three alloys. Aging in vacuum produces a subsurface 'damage region' consisting of an α(Ti3Al) surface layer with another layer of coarsened γ microstructure underneath. At 1000°C, this layer is greatest in the binary alloy and least in the Ti-47Al+W+B alloy. Specimens were 5.5% cold-forged and then aged at 1000°C to evaluate the effects of subsurface deformation caused during cutting of the specimens. Prior cold-deformation caused considerable recrystallization in the binary alloy, but almost none in the Ti-47Al+W+B alloy. The additions of W and B to a Ti-47Al alloy refine the fully-lamellar structure obtained by heat-treatment, and make it more resistant to lamellar coarsening (and recrystallization if cold deformed) during aging at 800-1000°C.",

keywords = "A. titanium aluminides (based on TiAl), B. microalloying, D. microstructure",

author = "Maziasz, {P. J.} and Ramanujan, {R. V.} and Liu, {C. T.} and Wright, {J. L.}",

year = "1997",

doi = "10.1016/S0966-9795(96)00070-2",

language = "English",

volume = "5",

pages = "83--95",

journal = "Intermetallics",

issn = "0966-9795",

publisher = "Elsevier Limited",

number = "2",

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TY - JOUR

T1 - Effects of B and W alloying additions on the formation and stability of lamellar structures in two-phase γ-TiAl

AU - Maziasz, P. J.

AU - Ramanujan, R. V.

AU - Liu, C. T.

AU - Wright, J. L.

PY - 1997

Y1 - 1997

N2 - The effects of additions of 140 appm B and 0.5 at.% W on the formation and stability of fully-lamellar structures in a Ti-47Al base alloy were studied. The fully-lamellar structure was formed by heat-treatment at 1400°C for 1 h (in vacuum) followed by furnace cooling. Stability was studied by aging these alloys for 168 h at 800, 1000 and 1200°C and making quantitative measurements of lamellar structure parameters (i.e. average lamellar spacing, α2-α2 spacing) using transmission electron microscopy (TEM) and hardness measurements. The B addition alone refines the lamellar structure relative to the binary TiAl alloy, but causes fragmented and discontinuous α2 lamellae. By contrast, W+B addition refines the lamellar structure and produces more uniform and continuous α2 lamellae. The as-heat-treated Ti-47Al+W+B alloy is harder than the other two alloys. Aging for 168 h at 800°C does not change the fine initial lamellar microstructure of any of these alloys. Aging at 1000°C significantly coarsens the Ti-47Al alloy, causes some coarsening in the Ti47Al+B alloy, but has little effect on the lamellar structure of the Ti-47Al+W+B alloy. Aging at 1200°C causes discontinuous coarsening and complete loss of the initial, fine, lamellar microstructure in all three alloys. Aging in vacuum produces a subsurface 'damage region' consisting of an α(Ti3Al) surface layer with another layer of coarsened γ microstructure underneath. At 1000°C, this layer is greatest in the binary alloy and least in the Ti-47Al+W+B alloy. Specimens were 5.5% cold-forged and then aged at 1000°C to evaluate the effects of subsurface deformation caused during cutting of the specimens. Prior cold-deformation caused considerable recrystallization in the binary alloy, but almost none in the Ti-47Al+W+B alloy. The additions of W and B to a Ti-47Al alloy refine the fully-lamellar structure obtained by heat-treatment, and make it more resistant to lamellar coarsening (and recrystallization if cold deformed) during aging at 800-1000°C.

AB - The effects of additions of 140 appm B and 0.5 at.% W on the formation and stability of fully-lamellar structures in a Ti-47Al base alloy were studied. The fully-lamellar structure was formed by heat-treatment at 1400°C for 1 h (in vacuum) followed by furnace cooling. Stability was studied by aging these alloys for 168 h at 800, 1000 and 1200°C and making quantitative measurements of lamellar structure parameters (i.e. average lamellar spacing, α2-α2 spacing) using transmission electron microscopy (TEM) and hardness measurements. The B addition alone refines the lamellar structure relative to the binary TiAl alloy, but causes fragmented and discontinuous α2 lamellae. By contrast, W+B addition refines the lamellar structure and produces more uniform and continuous α2 lamellae. The as-heat-treated Ti-47Al+W+B alloy is harder than the other two alloys. Aging for 168 h at 800°C does not change the fine initial lamellar microstructure of any of these alloys. Aging at 1000°C significantly coarsens the Ti-47Al alloy, causes some coarsening in the Ti47Al+B alloy, but has little effect on the lamellar structure of the Ti-47Al+W+B alloy. Aging at 1200°C causes discontinuous coarsening and complete loss of the initial, fine, lamellar microstructure in all three alloys. Aging in vacuum produces a subsurface 'damage region' consisting of an α(Ti3Al) surface layer with another layer of coarsened γ microstructure underneath. At 1000°C, this layer is greatest in the binary alloy and least in the Ti-47Al+W+B alloy. Specimens were 5.5% cold-forged and then aged at 1000°C to evaluate the effects of subsurface deformation caused during cutting of the specimens. Prior cold-deformation caused considerable recrystallization in the binary alloy, but almost none in the Ti-47Al+W+B alloy. The additions of W and B to a Ti-47Al alloy refine the fully-lamellar structure obtained by heat-treatment, and make it more resistant to lamellar coarsening (and recrystallization if cold deformed) during aging at 800-1000°C.

KW - A. titanium aluminides (based on TiAl)

KW - B. microalloying

KW - D. microstructure

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DO - 10.1016/S0966-9795(96)00070-2

M3 - Article

AN - SCOPUS:0031104543

SN - 0966-9795

VL - 5

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JO - Intermetallics

JF - Intermetallics

IS - 2

ER -

Effects of B and W alloying additions on the formation and stability of lamellar structures in two-phase γ-TiAl

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