2. Materials and Methods
We have examined the impact of processing route, total strain, and processing temperature on the mechanical behavior of copper (Cu)-tantalum (Ta) blended powder composites. Cu and Ta do not form compounds and have minimal solubility over their entire composition up to the solidus. Their differing crystal structures (Cu is FCC while Ta is BCC) and densities (8.96 g/cm3 for Cu and 16.65 g/cm3 for Ta) make them interesting model materials for high strain rate mechanical testing, in particular to study the influence of heterophase interfaces and large elastic impedance mismatch.
The consolidation process is optimized by initially conducting extrusions at ambient temperatures following a variety of routes followed by characterization of the microstructure and mechanical behavior of the consolidated material. Promising routes were selected for processing at 300 °C. Materials consolidated at these elevated temperatures were then mechanically tested in multiple orientations and at different strain rates in order to determine the effectiveness of the processing.
The Cu and Ta powders used in this investigation are pictured in Figure 1
. Their size and aspect ratio were found by analyzing scanning electron microscopy (SEM) images with the Fiji ImageJ software [40
The Cu powder was sourced from Alfa Aesar (Haverhill, MA, USA). It is spherical with an average diameter of 126 μm ± 15 μm and an aspect ratio of 1.2 ± 0.2. Ta powder was provided by H.C. Stark (Goslar, DEU) and is HRC grade capacitor powder. The particles possess an average diameter of 153 μm ± 47 μm and aspect ratio of 1.8 ± 0.6. Cans used for extrusion were made of 304 stainless steel. Each can was approximately 178 mm long, with a cross section of 25 mm × 25 mm and included a circular center cavity 140 mm long with diameter 12.5 mm. Plugs for the cans where 38 mm long and 12.5 mm in diameter and also made of 304 stainless steel. Powder handling was done in a glove box under an argon atmosphere.
Powders were combined in a 1:1 ratio by volume, equivalent to a mass ratio of 1:1.86. The powder mixture was then sealed inside a plastic wide-mouth Nalgene bottle. The Nalgene bottle was removed from the glove box and agitated inside a Turbula T2F Powder Mixer Shaker (WAB US Corp., Allendale, NJ, USA) for 20 min. Mixed powders were added to the cans inside the glove box and a metal plug inserted and sealed with black electrical tape. Prior to extrusion, cans were pre-compacted and sealed with a manually operated hydraulic press in order to minimize oxidation. Graphite sheet was wrapped around the cans to reduce friction during ECAE.
The cans were extruded using a 25.4 mm2 square cross section, sliding wall, zero degree fan angle ECAE tool at approximately 10 mm/s. For processing at elevated temperatures, the ECAE tool was pre-heated to the desired temperature. Billets were placed into the tool pre-upset to ensure good contact with the channel walls and to maintain the seal between the plug and can wall. They were allowed to reach thermal equilibrium with the tool for 30 min before extrusion.
Mechanical properties were obtained through uniaxial compression testing at a quasi-static strain rate of 10−3/s. Samples were prepared by sectioning with a silicon carbide cutting saw and mechanically polished down to 800—grit using silicon carbide polishing pads. The samples processed at ambient temperature measured 3 × 3 × 6 mm3 while those processed at elevated temperature measured 4 × 4 × 8 mm3. The length-to-width ratios of these samples are small enough to ensure that buckling is not a concern for these compression tests. The load frame used during testing has high compliance. Therefore, our stress-strain curves do not permit the reliable determination of elastic moduli.
During testing, samples were placed between tungsten carbide platens affixed to the load frame. Graphite sheet was used as a lubricant between the sample and the platens. Strain was measured at the tungsten carbide platens by an MTS model 632.53E-14 extensometer (MTS, Eden Prairie, MN, USA) with a gauge length of 12.7 mm. The platen/graphite sheet/sample/graphite sheet/platen stack nevertheless appears to have significant compliance (as evidenced in the different loading/unloading moduli shown in Supplementary Table S1
), so we do not believe our stress-strain curves permit reliable determination of elastic moduli. Material processed at elevated temperature was tested along the three primary extrusion orientations: longitudinal, extrusion, and flow directions. Two additional strain rates—10−2
/s and 10−1
/s—were investigated for the high temperature material along the extrusion direction. Material quantity limitations permitted a limited number of these additional tests. Compression testing was halted when either the load frame reached its safe limit, the load on the samples dropped, or deflection of the sample reached a critical state which might harm the test frame or extensometer.
Material microstructure was characterized using optical microscopy and SEM. Samples were hand polished with silicon carbide pads to 800 grit followed by polishing on a felt pad with colloidal silica and finished on a vibratory polisher with colloidal silica.
Conceptualization, Z.S.L., K.T.H. and M.J.D.; methodology, Z.S.L.; formal analysis, Z.S.L.; investigation, Z.S.L.; resources, Z.S.L.; data curation, Z.S.L.; writing—original draft preparation, Z.S.L.; writing—review & editing, K.T.H. and M.J.D.; visualization, Z.S.L.; supervision, K.T.H.; project administration, Z.S.L.; funding acquisition, M.J.D. All authors have read and agreed to the published version of the manuscript.
This material is based upon work supported by the US Department of Energy, National Nuclear Security Administration under Award No. DE-NA0003857.
Informed Consent Statement
Data Availability Statement
The authors thank R. E. Barber for support in EACE processing and B. Butler and J. Paramore for assistance with sample preparation and characterization. The raw/processed data required to reproduce these findings cannot be shared at this time due to technical or time limitations.
Conflicts of Interest
The authors declare no conflict of interest.
- Patel, M.; Sahu, S.K.; Singh, M.K. Mechanical, Tribological and Corrosion Behaviour of Aluminium Alloys and Particulate Reinforced Aluminium or Aluminium Alloy Metal Matrix Composites-A Review. i-Manag. J. Mater. Sci. 2020, 8, 40. [Google Scholar]
- Ray, A.K.; Venkateswarlu, K.; Chaudhury, S.; Das, S.; Kumar, B.R.; Pathak, L. Fabrication of TiN reinforced aluminium metal matrix composites through a powder metallurgical route. Mater. Sci. Eng. A 2002, 338, 160–165. [Google Scholar] [CrossRef]
- Bose, A.; Sadangi, R.; German, R.M. A review on alloying in tungsten heavy alloys. Suppl. Proc. Mater. Process. Interfaces 2012, 1, 453–465. [Google Scholar]
- Akhtar, F. An investigation on the solid state sintering of mechanically alloyed nano-structured 90W–Ni–Fe tungsten heavy alloy. Int. J. Refract. Met. Hard Mater. 2008, 26, 145–151. [Google Scholar] [CrossRef]
- Scudino, S.; Liu, G.; Sakaliyska, M.; Surreddi, K.B.; Eckert, J. Powder metallurgy of Al-based metal matrix composites reinforced with β-Al3Mg2 intermetallic particles: Analysis and modeling of mechanical properties. Acta Mater. 2009, 57, 4529–4538. [Google Scholar] [CrossRef]
- Varin, R. Intermetallic-reinforced light-metal matrix in-situ composites. Metall. Mater. Trans. A 2002, 33, 193–201. [Google Scholar] [CrossRef]
- Lei, T.; Tang, W.; Cai, S.-H.; Feng, F.-F.; Li, N.-F. On the corrosion behaviour of newly developed biodegradable Mg-based metal matrix composites produced by in situ reaction. Corros. Sci. 2012, 54, 270–277. [Google Scholar] [CrossRef]
- Sohag, M.A.Z.; Gupta, P.; Kondal, N.; Kumar, D.; Singh, N.; Jamwal, A. Effect of ceramic reinforcement on the microstructural, mechanical and tribological behavior of Al-Cu alloy metal matrix composite. Mater. Today Proc. 2020, 21, 1407–1411. [Google Scholar] [CrossRef]
- Zou, H.; Wang, Y.C.; Li, S.K. Effect of composition on microstructure and dynamic mechanical properties of W-Ni-Cu alloys. Appl. Sci. Mater. Sci. Inf. Technol. Ind. 2014, 513–517, 121–124. [Google Scholar] [CrossRef]
- Gong, X.; Fan, J.L.; Ding, F.; Song, M.; Huang, B.Y. Effect of tungsten content on microstructure and quasi-static tensile fracture characteristics of rapidly hot-extruded W-Ni-Fe alloys. Int. J. Refract. Met. Hard Mater. 2012, 30, 71–77. [Google Scholar] [CrossRef]
- Rieth, M.; Hoffmann, A. Influence of microstructure and notch fabrication on impact bending properties of tungsten materials. Int. J. Refract. Met. Hard Mater. 2010, 28, 679–686. [Google Scholar] [CrossRef]
- Das, J.; Rao, G.A.; Pabi, S.K.; Sankaranarayana, M.; Nandy, T.K. Thermo-mechanical processing, microstructure and tensile properties of a tungsten heavy alloy. Mater. Sci. Eng. A 2014, 613, 48–59. [Google Scholar] [CrossRef]
- Yu, Y.; Zhang, W.; Chen, Y.; Wang, E. Effect of swaging on microstructure and mechanical properties of liquid-phase sintered 93W-4.9(Ni, Co)-2.1Fe alloy. Int. J. Refract. Met. Hard Mater. 2014, 44, 103–108. [Google Scholar] [CrossRef]
- German, R.M.; Bose, A.; Mani, S.S. Sintering time and atmosphere influences on the microstructure and mechanical-properties of tungsten heavy alloys. Metall. Trans. A Phys. Metall. Mater. Sci. 1992, 23, 211–219. [Google Scholar] [CrossRef]
- Gong, X.; Fan, J.L.; Ding, F.; Song, M.; Huang, B.Y.; Tian, J.M. Microstructure and highly enhanced mechanical properties of fine-grained tungsten heavy alloy after one-pass rapid hot extrusion. Mater. Sci. Eng. A Struct. Mater. Prop. Microstruct. Process. 2011, 528, 3646–3652. [Google Scholar] [CrossRef]
- Levin, Z.S.; Ted Hartwig, K. Hardness and microstructure of tungsten heavy alloy subjected to severe plastic deformation and post-processing heat treatment. Mater. Sci. Eng. A 2015, 635, 94–101. [Google Scholar] [CrossRef]
- Barmouz, M.; Besharati Givi, M.K.; Seyfi, J. On the role of processing parameters in producing Cu/SiC metal matrix composites via friction stir processing: Investigating microstructure, microhardness, wear and tensile behavior. Mater. Charact. 2011, 62, 108–117. [Google Scholar] [CrossRef]
- Balachandran, S.; Barber, R.E.; Huang, Y.; Miao, H.; Parrell, J.A.; Griffin, R.B.; Hartwig, K.T. Influences of Different ECAE Routes on Filament Deformation in Cu Clad Nb Composite Wires. IEEE Trans. Appl. Supercond. 2011, 21, 2584–2587. [Google Scholar] [CrossRef]
- Kunčická, L.; Kocich, R.; Klečková, Z. Effects of Sintering Conditions on Structures and Properties of Sintered Tungsten Heavy Alloy. Materials 2020, 13, 2338. [Google Scholar] [CrossRef]
- Gero, R.; Borukhin, L.; Pikus, I. Some structural effects of plastic deformation on tungsten heavy metal alloys. Mater. Sci. Eng. A Struct. Mater. Prop. Microstruct. Process. 2001, 302, 162–167. [Google Scholar] [CrossRef]
- Suresh, S. Fundamentals of Metal-Matrix Composites; Elsevier: Amsterdam, The Netherlands, 2013. [Google Scholar]
- Elliott, R. Eutectic Solidification Processing: Crystalline and Glassy Alloys; Elsevier: Amsterdam, The Netherlands, 2013. [Google Scholar]
- Samal, C.; Parihar, J.y.; Chaira, D. The effect of milling and sintering techniques on mechanical properties of Cu–graphite metal matrix composite prepared by powder metallurgy route. J. Alloy. Compd. 2013, 569, 95–101. [Google Scholar] [CrossRef]
- Balachandran, S.; Smathers, D.B.; Walsh, R.P.; Starch, W.L.; Lee, P.J. High-Strength Cu–Ta–W Composite. IEEE Trans. Appl. Supercond. 2019, 29, 1–4. [Google Scholar] [CrossRef]
- Alizadeh, M.; Salahinejad, E. A comparative study on metal–matrix composites fabricated by conventional and cross accumulative roll-bonding processes. J. Alloy. Compd. 2015, 620, 180–184. [Google Scholar] [CrossRef]
- Zeng, L.F.; Gao, R.; Fang, Q.F.; Wang, X.P.; Xie, Z.M.; Miao, S.; Hao, T.; Zhang, T. High strength and thermal stability of bulk Cu/Ta nanolamellar multilayers fabricated by cross accumulative roll bonding. Acta Mater. 2016, 110, 341–351. [Google Scholar] [CrossRef]
- Mathaudhu, S.N.; Hartwig, K.T.; Karaman, I. Consolidation of blended powders by severe plastic deformation to form amorphous metal matrix composites. J. Non-Cryst. Solids 2007, 353, 185–193. [Google Scholar] [CrossRef]
- Karaman, I.; Haouaoui, M.; Maier, H. Nanoparticle consolidation using equal channel angular extrusion at room temperature. J. Mater. Sci. 2007, 42, 1561–1576. [Google Scholar] [CrossRef]
- Levin, Z.S.; Wang, X.; Kaynak, M.; Karaman, I.; Hartwig, K.T. Strength and ductility of powder consolidated ultrafine-grain tantalum. Int. J. Refract. Met. Hard Mater. 2019, 80, 73–84. [Google Scholar] [CrossRef]
- Robertson, J.; Im, J.T.; Karaman, I.; Hartwig, K.T.; Anderson, I.E. Consolidation of amorphous copper based powder by equal channel angular extrusion. J. Non-Cryst. Solids 2003, 317, 144–151. [Google Scholar] [CrossRef]
- Subramanian, P.R.; Laughlin, D.E. The Cu-Ta (Copper-Tantalum) system. Bull. Alloy Phase Diagr. 1989, 10, 652–655. [Google Scholar] [CrossRef]
- Kaufman, L. Coupled thermochemical and phase diagram data for tantalum based binary alloys. Calphad 1991, 15, 243–259. [Google Scholar] [CrossRef]
- Darling, K.; Tschopp, M.; Guduru, R.; Yin, W.; Wei, Q.; Kecskes, L. Microstructure and mechanical properties of bulk nanostructured Cu–Ta alloys consolidated by equal channel angular extrusion. Acta Mater. 2014, 76, 168–185. [Google Scholar] [CrossRef]
- Hornbuckle, B.C.; Rojhirunsakool, T.; Rajagopalan, M.; Alam, T.; Pun, G.P.P.; Banerjee, R.; Solanki, K.N.; Mishin, Y.; Kecskes, L.J.; Darling, K.A. Effect of Ta solute concentration on the microstructural evolution in immiscible Cu-Ta alloys. Jom 2015, 67, 2802–2809. [Google Scholar] [CrossRef]
- Rajagopalan, M.; Darling, K.; Turnage, S.; Koju, R.K.; Hornbuckle, B.; Mishin, Y.; Solanki, K.N. Microstructural evolution in a nanocrystalline Cu-Ta alloy: A combined in-situ TEM and atomistic study. Mater. Des. 2017, 113, 178–185. [Google Scholar] [CrossRef]
- Rajagopalan, M.; Darling, K.A.; Kale, C.; Turnage, S.A.; Koju, R.K.; Hornbuckle, B.C.; Mishin, Y.; Solanki, K.N. Nanotechnology enabled design of a structural material with extreme strength as well as thermal and electrical properties. Mater. Today 2019, 31, 10–20. [Google Scholar] [CrossRef]
- Segal, V.M. Materials processing by simple shear. Mater. Sci. Eng. A 1995, 197, 157–164. [Google Scholar] [CrossRef]
- Segal, V.M. Engineering and commercialization of equal channel angular extrusion (ECAE). Mater. Sci. Eng. A 2004, 386, 269–276. [Google Scholar] [CrossRef]
- Levin, Z.S.; Hartwig, K.T. Strong ductile bulk tungsten. Mater. Sci. Eng. A 2017, 707, 602–611. [Google Scholar] [CrossRef]
- Schindelin, J.; Arganda-Carreras, I.; Frise, E.; Kaynig, V.; Longair, M.; Pietzsch, T.; Preibisch, S.; Rueden, C.; Saalfeld, S.; Schmid, B.; et al. Fiji: An open-source platform for biological-image analysis. Nat. Methods 2012, 9, 676–682. [Google Scholar] [CrossRef] [PubMed]
- Springs, J.; Kao, Y.; Srivastava, A.; Levin, Z.; Barber, R.; Hartwig, K. Strength and electrical resistivity of heavily worked copper. IOP Conf. Ser. Mater. Sci. Eng. 2017, 279, 012003. [Google Scholar] [CrossRef]
SEM micrographs of initial Cu (left) and Ta (right) powders used in consolidation.
Micrographs on the Flow plane of Cu-Ta composites consolidated at ambient temperature by ECAE routes 1A, 2A, 2A×2A, 2C, and 4E.
Experimental compression stress-strain curves for Cu-Ta composites consolidated at ambient temperature.
3-D representation of microstructure along three different sectioning planes in Cu-Ta composites consolidated at 300 °C by routes 4E and 4Bc.
Compression stress-strain curves for Cu-Ta composites consolidated at 300 °C. For comparison, the stress strain curve for route 4E consolidation at ambient temperature is also shown.
Compression stress-strain curves for Cu-Ta composites consolidated at 300 °C for tests along the extrusion direction (ED), longitudinal direction (LD), and flow direction (FD), (a) by route 4E, and (b) by route 4Bc.
Experimental compression stress-strain curves of Cu50Ta consolidated at 300 °C tested at strain rates of 10−3, 10−2, 10−1, s−1 along the extrusion direction (ED). (a) By route 4E, and (b) by route 4Bc.
Summary of total accumulated strain, Vickers hardness, % area of Cu phase, and phase boundary trace length per unit area for each ECAE processing route.
|Route||Strain||Hardness HV300||% Cu Area||Interface Trace Length per Unit Area [μm−1]|
|1A Cu-Ta||1.15||164 ± 12||46 ± 5||4 ± 0.3|
|2A Cu-Ta||2.3||177 ± 12||42 ± 5||6 ± 0.7|
|2A×2A Cu-Ta||4.6||190 ± 18||47 ± 6||3.6 ± 0.7|
|2C Cu-Ta||2.3||174 ± 23||42 ± 4||4.6 ± 0.7|
|4E Cu-Ta||4.6||188 ± 25||53 ± 4||3.1 ± 0.6|
Summary of phase boundary trace length per unit area and % area of Cu phase for Cu-Ta composites processed at 300 °C.
|Processing||Oreintation||% Interface Trace Length per Unit Area [μm−1]||% Cu Area|
|4E||Longitudinal||3.5||3.7 ± 0.2||39||46 ± 7|
|4Bc||Longitudinal||4.4||4.5 ± 0.4||41||43 ± 4|
Summary of compression test results on Cu-Ta composites processed by routes 4E and 4Bc.
|Route||Processing Temperature||Strain Rate (s−1)||Testing Direction||Yield Stress (MPa)||Flow Stress at ε = 0.05 (MPa)||Flow Stress at ε = 0.1 (MPa)|
|4E||300 °C||10−3||ED||349 ± 25||476 ± 4||533 ± 2|
|-||-||10−3||FD||387 ± 1||513 ± 9||563 ± 4|
|-||-||10−3||LD||383 ± 9||518 ± 13||573 ± 21|
|4Bc||300 °C||10−3||ED||350 ± 6||488 ± 12||547 ± 12|
|-||-||10−3||FD||379 ± 4||521 ± 2||579 ± 1|
|-||-||10−3||LD||388 ± 6||504 ± 6||562 ± 9|
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.
© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).