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Liu, Y., Cai, X., Sun, Z., Jiao, X., Akhtar, F., Wang, J. & Feng, P. (2018). A novel fabrication strategy for highly porous FeAl/Al2O3 composite by thermal explosion in vacuum. Vacuum, 149, 225-230
Open this publication in new window or tab >>A novel fabrication strategy for highly porous FeAl/Al2O3 composite by thermal explosion in vacuum
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2018 (English)In: Vacuum, ISSN 0042-207X, Vol. 149, p. 225-230Article in journal (Refereed) Published
Abstract [en]

The high porosity of FeAl/Al2O3 composites was successfully prepared via a low-energy consumption method of thermal explosion (TE) in vacuum from reactant mixtures of Fe, Al and Fe2O3. The temperature profiles, phase compositions, microstructure, porosity and pore size of the products were investigated. The TE reactions were ignited between 639 and 648 °C and maximum combustion temperatures reached to 1196–1867 °C. XRD patterns showed that FeAl, Fe2Al5 and Al2O3 were formed via TE reaction, and FeAl and Al2O3 were evolved as dominant phase after the final sintering at 1100 °C. The FeAl/Al2O3 composites exhibited an interconnected pore structure with porosities and pore size of 52–61% and 27–32 μm, respectively.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-67230 (URN)10.1016/j.vacuum.2017.12.043 (DOI)000425576100038 ()2-s2.0-85039993183 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-01-11 (andbra)

Available from: 2018-01-11 Created: 2018-01-11 Last updated: 2018-03-15Bibliographically approved
Cai, X., Liu, Y., Wang, X., Jiao, X., Feng, P. & Akhtar, F. (2018). Fabrication of Highly Porous CuAl Intermetallic by Thermal Explosion Using NaCl Space Holder. JOM: The Member Journal of TMS, 70(10), 2173-2178
Open this publication in new window or tab >>Fabrication of Highly Porous CuAl Intermetallic by Thermal Explosion Using NaCl Space Holder
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2018 (English)In: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 70, no 10, p. 2173-2178Article in journal (Refereed) Published
Abstract [en]

A high-porosity CuAl-based intermetallic compound with composition Cu-50 at.% Al has been successfully prepared by thermal explosion (TE) using NaCl as space holder. The results showed that the NaCl particles were completely removed from the green compact by water leaching. The temperature of the specimen during the TE and the evolution of the porous microstructure were investigated. The TE was ignited at 560°C, and the specimen temperature increased to 775°C in 3 s, resulting in formation of intermetallic CuAl and CuAl2 phases in the final product. A porous CuAl-based intermetallic compound with up to 62 vol.% open porosity was produced when adding 60 vol.% NaCl. The compound exhibited a bimodal pore size structure, including large pores (200 μm to 300 μm) that replicated the NaCl particles and small pores (5 μm to 10 μm) interspersed in the pore walls. Moreover, the large pores were interconnected by channels and formed an open CuAl-based intermetallic cellular structure, having great potential for use in heat exchange and filtration applications.

Place, publisher, year, edition, pages
The Minerals, Metals, and Materials Society, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-70257 (URN)10.1007/s11837-018-3035-5 (DOI)000445161500036 ()2-s2.0-85050195385 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-09 (inah)

Available from: 2018-08-07 Created: 2018-08-07 Last updated: 2018-10-09Bibliographically approved
Alvi, S. & Akhtar, F. (2018). High temperature tribology of polymer derived ceramic composite coatings. Scientific Reports, 8, 1-10, Article ID 15105.
Open this publication in new window or tab >>High temperature tribology of polymer derived ceramic composite coatings
2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, p. 1-10, article id 15105Article in journal (Refereed) Published
Abstract [en]

Polymer derived ceramic (PDC) composite coatings were deposited on AISI 304 substrates using siloxane based preceramic polymer polymethlysilsquioxane (PMS) and ZrSi2 as active filler or Ag as passive filler. The tribological performance of the composite coatings was evaluated at room temperature and moderately high temperatures (150 °C, 200 °C, 300 °C and 400 °C). The composite coatings showed low coefficient of friction (COF), µ, from 0.08 to 0.2 for SiOC-ZrSi2 composite coatings, and from 0.02 to 0.3 for SiOC-Ag composite coatings, at room temperature with increasing normal load from 1 to 5 N. High temperature tribology tests showed high COF values from 0.4 to 1 but low wear for SiOC-ZrSi2 coating, and low COF from 0.2 to 0.3 for SiOC-Ag coatings at lower temperature ranges. Low load friction tests at room temperature showed negligible wear in SiOC-ZrSi2 coatings, suggesting good wear resistant and lubricating properties due to formation of t-ZrO2 and carbon. Low COF and high amount of wear was observed in SiOC-Ag composite coatings at room temperature due to high ductility of Ag and smearing of wear debris in the wear track. The coatings and wear tracks were characterized to evaluate the lubrication and wear behavior.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-71176 (URN)10.1038/s41598-018-33441-8 (DOI)
Note

Validering;2018;Nivå 2;2018-10-12 (johcin)

Available from: 2018-10-12 Created: 2018-10-12 Last updated: 2018-10-12Bibliographically approved
Jiang, Z., Zhu, G., Feng, P. & Akhtar, F. (2018). In Situ Fabrication and Properties of 0.4MoB-0.1SiC-xMoSi2 Composites by Self-propagating Synthesis and Hot-press sintering. Ceramics International, 44(1), 51-56
Open this publication in new window or tab >>In Situ Fabrication and Properties of 0.4MoB-0.1SiC-xMoSi2 Composites by Self-propagating Synthesis and Hot-press sintering
2018 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 44, no 1, p. 51-56Article in journal (Refereed) Published
Abstract [en]

Mo, Si and B4C powders were used to fabricate 0.4MoB-0.1SiC-xMoSi2 composites by self-propagating high-temperature synthesis (SHS) and hot pressing (HP). The effects of MoSi2 content (x=1, 0.75, 0.5 and 0.25) on phase composition, microstructure and properties of the composites were investigated. The results showed that the 0.4MoB-0.1SiC-xMoSi2 composite exhibited Vickers hardness of 10.7–15.2 GPa, bending strength of 337–827 MPa and fracture toughness of 4.9–7.0 MPa∙m1/2. The fracture toughness increased with the increasing volume fraction of MoB and SiC particles which were promoted by the toughening mechanisms, such as crack bridging, cracks deflection and crack branching. Moreover, the electrical resistivity showed an increasing trend with decreasing volume fraction of MoSi2.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-66006 (URN)10.1016/j.ceramint.2017.08.207 (DOI)000416877900007 ()
Note

Validerad;2017;Nivå 2;2017-11-09 (andbra)

Available from: 2017-10-09 Created: 2017-10-09 Last updated: 2017-12-21Bibliographically approved
Jiao, X., Wang, X., Feng, P., Liu, Y., Zhang, L. & Akhtar, F. (2018). Microstructure Evolution and Pore Formation Mechanism of Porous TiAl3 Intermetallics via Reactive Sintering. Acta Metallurgica Sinica (English Letters), 31(4), 440-448
Open this publication in new window or tab >>Microstructure Evolution and Pore Formation Mechanism of Porous TiAl3 Intermetallics via Reactive Sintering
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2018 (English)In: Acta Metallurgica Sinica (English Letters), ISSN 1006-7191, E-ISSN 2194-1289, Vol. 31, no 4, p. 440-448Article in journal (Refereed) Published
Abstract [en]

Porous TiAl3 intermetallics were fabricated through vacuum reactive sintering from Ti–75Al at.% elemental powder mixture. The phase compositions, expansion behaviors, pore characteristics and microstructure evolution of TiAl3 intermetallics were investigated, and the pore formation mechanism was also proposed. It was found that the actual temperature of compacts showed an acute climb from 668 to 1244 °C in 166s, while the furnace temperature maintained the linear growth of 5 °C/min, which indicated that an obvious thermal explosion (TE) reaction occurred during sintering, and only single-phase TiAl3 intermetallic was synthesized in TE products. The open porosity increased from 22.2 (green compact) to 32.8% after reactive diffusion sintering at 600 °C and rised to 58.7% after TE, then decreased to 51.2% after high-temperature homogenization at 1100 °C. Therefore, TE reaction is the dominated pore formation mechanism of porous TiAl3 intermetallics. The pore evolution in porous TiAl3 intermetallics occurred by the following mechanisms: certain intergranular pores remained among powder particles of green compact, then low-temperature sintering resulted in a further increase in porosity due to the Kirkendall effect. Moreover, TE reaction gave rise to a dramatic volume expansion because of the rapid increase in temperature, and high-temperature sintering caused densification and a slight shrinkage.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Intermetallics, Porous materials, Powder metallurgy, Reaction synthesis, Thermal explosion synthesis
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-66364 (URN)10.1007/s40195-017-0663-7 (DOI)000429386300011 ()
Note

Validerad;2018;Nivå 2;2018-03-14 (rokbeg)

Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2018-04-26Bibliographically approved
Cai, X., Liu, Y., Wang, X., Jiao, X., Wang, J., Akhtar, F. & Feng, P. (2018). Oxidation Resistance of Highly Porous Fe-Al Foams Prepared by Thermal Explosion. Metallurgical and Materials Transactions. A, 49A(8), 3683-3691
Open this publication in new window or tab >>Oxidation Resistance of Highly Porous Fe-Al Foams Prepared by Thermal Explosion
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2018 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49A, no 8, p. 3683-3691Article in journal (Refereed) Published
Abstract [en]

Open-cell Fe-Al intermetallic foams were successfully prepared by a simple and energy-saving thermal explosion (TE) process. The effects of the Fe/Al molar ratio (Fe-(40–50) at. pct Al) and thermal treatment temperature on the TE temperature profile, phase composition, pore characteristics, and oxidation resistance of the prepared foams were investigated. The results showed that the Al content significantly influenced the ignition (Tig) and combustion (Tc) temperatures of the TE process; in particular, as the Al content decreased, Tig increased gradually from 623 °C to 636 °C and Tc decreased from 1059 °C to 981 °C. FeAl was identified as the dominant phase in the thermally treated foams. The Fe-Al intermetallic foams displayed an open porosity of 60 vol pct, with pores connected with each other to form an open pore structure. The formation of the pores was attributed to the expansion of interparticle pores in the pressed body during the TE reaction. X-ray photoelectron spectroscopy analysis of the Fe-50Al foam showed that the Al 2p and O 1s binding energies were 74.5 eV and at 531.4 eV, respectively. The formation of a surface alumina layer in the early stages of the oxidation process resulted in the parabolic oxidation rate law, and the Fe-50Al foams exhibited an excellent resistance to oxidation at 650 °C in air. These results suggest that the synthesized Fe-Al foams represent promising materials for applications involving an oxidizing environment and high temperatures.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-69047 (URN)10.1007/s11661-018-4680-6 (DOI)000436905100049 ()2-s2.0-85047921551 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-08-06 (rokbeg)

Available from: 2018-06-01 Created: 2018-06-01 Last updated: 2018-08-06Bibliographically approved
Saeidi, K., Neikter, M., Olsen, J., Shen, Z. J. & Akhtar, F. (2017). 316L stainless steel designed to withstand intermediate temperature. Materials & design, 135, 1-8
Open this publication in new window or tab >>316L stainless steel designed to withstand intermediate temperature
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2017 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 135, p. 1-8Article in journal (Refereed) Published
Abstract [en]

Austenitic stainless steel 316L was fabricated for withstanding elevated temperature by selective laser melting (SLM). Tensile tests at 800 °C were carried out on laser melted 316L with two different strain rates of 0.05 S− 1 and 0.25 S− 1. The laser melted 316L showed tensile strength of approximately 400 MPa at 800 °C, which was superior to conventional 316L. Analysis of fracture surface showed that the 316L fractured in mixed mode, ductile and brittle fracture, with an elongation of 18% at 800 °C. In order to understand the mechanical response, laser melted 316L was thermally treated at 800 °C for microstructure and phase stability. X-ray diffraction (XRD) and Electron back scattered diffraction (EBSD) of 316L treated at 800 °C disclosed a textured material with single austenitic phase. SEM and EBSD showed that the characteristic and inherent microstructure of laser melted 316L, consisting of elongated grains with high angle grain boundaries containing subgrains with a smaller misorientation, remained similar to as-built SLM 316L during hot tensile test at 800 °C. The stable austenite phase and its stable hierarchical microstructure at 800 °C led to the superior mechanical response of laser melted 316L.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-65565 (URN)10.1016/j.matdes.2017.08.072 (DOI)000413236300001 ()2-s2.0-85028815416 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-09-11 (andbra)

Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2018-03-05Bibliographically approved
Zhang, H., Feng, P. & Akhtar, F. (2017). Aluminium matrix tungsten aluminide and tungsten reinforced composites by solid-state diffusion mechanism. Scientific Reports, 7(1), Article ID 12391.
Open this publication in new window or tab >>Aluminium matrix tungsten aluminide and tungsten reinforced composites by solid-state diffusion mechanism
2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, no 1, article id 12391Article in journal (Refereed) Published
Abstract [en]

In-situ processing of tungsten aluminide and tungsten reinforced aluminium matrix composites from elemental tungsten (W) and aluminium (Al) was investigated by thermal analysis and pulsed current processing (PCP). The formation mechanism of tungsten aluminides in 80 at.% Al-20 at.% W system was controlled by atomic diffusion. The particle size of W and Al in the starting powder mixture regulated the phase formation and microstructure. PCP of micron sized elemental Al and W resulted in formation of particulate reinforcements, W, Al4W and Al12W, dispersed in Al matrix. W particles were surrounded by a ~3 μm thick dual-layer structure of Al12W and Al4W. The hardness of Al matrix, containing Al12W reinforcements, was increased by 50% compared to pure Al, from 0.3 GPa to 0.45 GPa and W reinforcements showed a hardness of 4.35 GPa. On PCP of 80 at.% Al-20 at.% W mixture with particle size of W and Al ~70 nm, resulted in formation of Al4W as major phase along with small fractions of Al5W and unreacted W phase. This suggested strongly that the particle size of the starting elemental Al and W could be the controlling parameter in processing and tailoring of phase evolution, microstructure of particulate reinforced Al matrix composite.

Place, publisher, year, edition, pages
Nature Publishing Group, 2017
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-65925 (URN)10.1038/s41598-017-12302-w (DOI)000412000100006 ()28959027 (PubMedID)2-s2.0-85030115396 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-10-03 (andbra)

Available from: 2017-10-03 Created: 2017-10-03 Last updated: 2018-06-14Bibliographically approved
Ogunmuyiwa, E. N., Sacks, N., Bergström, L. M. & Akhtar, F. (2017). Effect of 10wt%VC on the friction and sliding wear of spark plasma sintered WC-12wt%Co cemented carbides (ed.). Tribology Transactions, 60(2), 276-283
Open this publication in new window or tab >>Effect of 10wt%VC on the friction and sliding wear of spark plasma sintered WC-12wt%Co cemented carbides
2017 (English)In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 60, no 2, p. 276-283Article in journal (Refereed) Published
Abstract [en]

The effect of 10wt%VC addition on the friction and sliding wear response of WC-12wt%Co cemented carbides produced by spark plasma sintering (SPS) was studied. The SPS of WC-12wt%Co alloys with and without 10wt% VC, at 1100 °C and 1130 °C respectively, yielded dense materials with minimal porosity. No eta phase was found in any of the alloys. The WC-12wt%Co-10wt%VC alloy showed the formation of the hard WV4C5 phase, which improved the alloy hardness. Friction and dry sliding wear tests were done using a ball-on-disk configuration under an applied load of 10 N, a sliding speed of 0.26 m.s−1, and a 100Cr-steel ball used as the counterface. A significant improvement in the sliding wear response of the harder and more fracture tough WC-12wt%Co-10wt%VC alloy compared to the WC-12wt%Co alloy was found. Analysis of the worn surfaces by scanning electron microscopy showed that the wear mechanisms included plastic deformation, preferential binder removal, adhesion, and carbide grain cracking and fragmentation.  

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-15071 (URN)10.1080/10402004.2016.1159360 (DOI)000396779900009 ()2-s2.0-84980315835 (Scopus ID)e8855eea-d52a-42ba-9e60-6de9604df5cf (Local ID)e8855eea-d52a-42ba-9e60-6de9604df5cf (Archive number)e8855eea-d52a-42ba-9e60-6de9604df5cf (OAI)
Note

Validerad; 2017; Nivå 2; 2017-02-16 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Jiao, X., Wang, X., Kang, X., Feng, P., Zhang, L. & Akhtar, F. (2017). Effect of heating rate on porous TiAl-based intermetallics synthesized by thermal explosion. Materials and Manufacturing Processes, 32(5), 489-494
Open this publication in new window or tab >>Effect of heating rate on porous TiAl-based intermetallics synthesized by thermal explosion
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2017 (English)In: Materials and Manufacturing Processes, ISSN 1042-6914, E-ISSN 1532-2475, Vol. 32, no 5, p. 489-494Article in journal (Refereed) Published
Abstract [en]

TiAl-based porous materials were synthesized by a novel process of thermal explosion (TE) reaction. The effect of heating rate on expansion behavior of powder assemblies, phase compositions and pore structures were investigated. Results showed that the actual temperature of specimen increased rapidly from 655-661 °C (furnace temperature) to 1018–1136 °C (combustion temperature) in a short time interval of 25–55 s, indicating that an obvious TE reaction occurred at different heating rates (1, 2, 5 and 10°C · min−1). TE reaction in Ti/Al powder assemblies resulted in formation of open-celled TiAl-based intermetallics. When the heating rate was set at 5 °C · min−1, the maximum open porosity of 59% was obtained in Ti-Al bodies, which experienced the highest combustion temperature (1136°C) and underwent maximum volume expansion (48%). The pore size distribution was uniform and pores were interconnected in TE products.

National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-59935 (URN)10.1080/10426914.2016.1232826 (DOI)000395350100006 ()2-s2.0-85000961915 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-03-06 (rokbeg)

Available from: 2016-10-25 Created: 2016-10-25 Last updated: 2018-07-10Bibliographically approved
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