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Title: Structure-processing correlations and mechanical properties in freeze-cast Ti-6Al-4V with highly aligned porosity and a lightweight Ti-6Al-4V-PMMA composite with excellent energy absorption capability

Abstract

In contrast to freeze-cast ceramics and polymers, few freeze-cast metals have been described, to date. This systematic study on structure-processing correlations in freeze-cast Ti-6Al-4V scaffolds reports how processing parameters determine the architecture formed during the directional solidification of water-based metal slurries and after sintering. Additionally, sedimentation in the slurry during freezing and volume shrinkage during burnout and sintering were found to significantly affect both structure and properties of the scaffolds. In using two freezing rates, 1 and 10 °C min -1, two water-based polymer solutions as binders (chitosan and carboxymethyl cellulose) and two different metal volume fractions in the slurry, 20 and 30 vol%, Ti-6Al-4V scaffolds could be prepared with pore length, width, and porosity ranging from 41 to 523 μm, 14.5–76.5 μm, and 65 to 34%, respectively. Their compressive strength, stiffness, and toughness (work to 20% strain) fall in the range of 83–412 MPa, 7–29 GPa, and 14–122 MJ m -3, respectively. In order to improve the properties a select composition was infiltrated with poly(methyl methacrylate). This increased the average yield strength by a factor of 2.3 from 83 to 193 MPa and the average toughness (work to 50% strain) by a factor of 2.7 from 28.1 to 76.8more » MJ m -3.« less

Authors:
; ;
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE; U.S. Dept. of Education
OSTI Identifier:
1344336
Report Number(s):
LA-UR-16-24482
Journal ID: ISSN 1359-6454
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 132; Journal Issue: C; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Material Science; Directional Solidification, Honeycombs, Porous metals, Sintering, Toughness

Citation Formats

Weaver, Jordan S., Kalidindi, Surya R., and Wegst, Ulrike G. K. Structure-processing correlations and mechanical properties in freeze-cast Ti-6Al-4V with highly aligned porosity and a lightweight Ti-6Al-4V-PMMA composite with excellent energy absorption capability. United States: N. p., 2017. Web. doi:10.1016/j.actamat.2017.02.031.
Weaver, Jordan S., Kalidindi, Surya R., & Wegst, Ulrike G. K. Structure-processing correlations and mechanical properties in freeze-cast Ti-6Al-4V with highly aligned porosity and a lightweight Ti-6Al-4V-PMMA composite with excellent energy absorption capability. United States. doi:10.1016/j.actamat.2017.02.031.
Weaver, Jordan S., Kalidindi, Surya R., and Wegst, Ulrike G. K. Sun . "Structure-processing correlations and mechanical properties in freeze-cast Ti-6Al-4V with highly aligned porosity and a lightweight Ti-6Al-4V-PMMA composite with excellent energy absorption capability". United States. doi:10.1016/j.actamat.2017.02.031. https://www.osti.gov/servlets/purl/1344336.
@article{osti_1344336,
title = {Structure-processing correlations and mechanical properties in freeze-cast Ti-6Al-4V with highly aligned porosity and a lightweight Ti-6Al-4V-PMMA composite with excellent energy absorption capability},
author = {Weaver, Jordan S. and Kalidindi, Surya R. and Wegst, Ulrike G. K.},
abstractNote = {In contrast to freeze-cast ceramics and polymers, few freeze-cast metals have been described, to date. This systematic study on structure-processing correlations in freeze-cast Ti-6Al-4V scaffolds reports how processing parameters determine the architecture formed during the directional solidification of water-based metal slurries and after sintering. Additionally, sedimentation in the slurry during freezing and volume shrinkage during burnout and sintering were found to significantly affect both structure and properties of the scaffolds. In using two freezing rates, 1 and 10 °C min-1, two water-based polymer solutions as binders (chitosan and carboxymethyl cellulose) and two different metal volume fractions in the slurry, 20 and 30 vol%, Ti-6Al-4V scaffolds could be prepared with pore length, width, and porosity ranging from 41 to 523 μm, 14.5–76.5 μm, and 65 to 34%, respectively. Their compressive strength, stiffness, and toughness (work to 20% strain) fall in the range of 83–412 MPa, 7–29 GPa, and 14–122 MJ m-3, respectively. In order to improve the properties a select composition was infiltrated with poly(methyl methacrylate). This increased the average yield strength by a factor of 2.3 from 83 to 193 MPa and the average toughness (work to 50% strain) by a factor of 2.7 from 28.1 to 76.8 MJ m-3.},
doi = {10.1016/j.actamat.2017.02.031},
journal = {Acta Materialia},
number = C,
volume = 132,
place = {United States},
year = {Sun Feb 12 00:00:00 EST 2017},
month = {Sun Feb 12 00:00:00 EST 2017}
}

Journal Article:
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  • Mechanical behaviors at 538 C, including tensile and creep properties, were investigated for both the Ti-6Al-4V alloy and the Ti-6Al-4V composite reinforced with 10 wt pct TiC particulates fabricated by cold and hot isostatic pressing (CHIP). It was shown that the yield strength (YS) and ultimate tensile strength (UTS) of the composite were greater than those of the matrix alloy at the strain rates ranging from approximately 10{sup {minus}5} to 10{sup {minus}3} s{sup {minus}1}. However, the elongation of the composite material was substantially lower than that of the matrix alloy. The creep resistance of the composite was superior to thatmore » of the matrix alloy. The data of minimum creep strain rate vs applied stress for the composite can be fit to a power-law equation, and the stress exponent values of 5 and 8 were obtained for applied stress ranges of 103 to 232 MPa and 232 to 379 MPa, respectively. The damage mechanisms were different for the matrix alloy and the composite, as demonstrated by the scanning electron microscopy (SEM) observation of fracture surfaces and the optical microscopy examination of the regions adjacent to the fracture surface. The tensile-tested matrix alloy showed dimpled fracture, while the creep-tested matrix alloy exhibited preferentially interlath and intercolony cracking. The failure of the tensile-tested and creep-tested composite material was controlled by the cleavage failure of the particulates, which was followed by the ductile fracture of the matrix.« less
  • This study represents an exploratory characterization and comparison of electron-beam melted (EBM) or rapid manufacturing (RM) of Ti-6Al-4V components (from nominal 30 {mu}m diameter powder) with wrought products. Acicular {alpha} and associated {beta} microstructures observed by optical metallography and electron microscopy (SEM and TEM) are compared along with corresponding tensile test and hardness data; including the initial powder particles where the Vickers microindentation hardness averaged 5.0 GPa in comparison with the fully dense, EB manufactured product with an average microindentation hardness ranging from 3.6 to 3.9 GPa. This compared with wrought products where the Vickers microindentation hardness averaged 4.0 GPa.more » Values of UTS for the EBM samples averaged 1.18 GPa for elongations ranging from 16 to 25%. Biomaterials/biomedical applications of EBM prototypes in direct prosthesis or implant manufacturing from CT or MRI data are discussed in the context of this work, especially prospects for tailoring physical properties through EB control to achieve customized and optimized implant and prosthetic products direct from CT-scans.« less
  • Cited by 1
  • This work studied the effect of processing on the elevated-temperature [728 K (455 C)] fatigue deformation behavior of Ti-6Al-4V-1B for maximum applied stresses between 300 to 700 MPa (R = 0.1, 5 Hz). The alloy was evaluated in the as-cast form as well as in three wrought forms: cast-and-extruded, powder metallurgy (PM) rolled, and PM extruded. Processing caused significant differences in the microstructure, which in turn impacted the fatigue properties. The PM-extruded material exhibited a fine equiaxed {alpha} + {beta} microstructure and the greatest fatigue resistance among all the studied materials. The {beta}-phase field extrusion followed by cooling resulted inmore » a strong {alpha}-phase texture in which the basal plane was predominately oriented perpendicular to the extrusion axis. The TiB whiskers were also aligned in the extrusion direction. The {alpha}-phase texture in the extrusions resulted in tensile-strength anisotropy. The tensile strength in the transverse orientation was lower than that in the longitudinal orientation, but the strength in the transverse orientation remained greater than that for the as-cast Ti-6Al-4V. The ratcheting behavior during fatigue is also discussed.« less