Advanced Mechanical Testing of Powder Metallurgy Alloys

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 May 2018) | Viewed by 20891

Special Issue Editor

Mechanical Engineering, Dalhousie University, PO Box 15000, Halifax, NC B3H 4R2, Canada
Interests: powder metallurgy processing of light metals; alloy development; mechanical testing; powder forging

Special Issue Information

Dear Colleagues,

The development of advanced powder metallurgy materials and processing technologies has been a central pillar of innovation within the global PM community for decades.  Indeed, the outcomes of these endeavors have underpinned a prolific expansion in the scope of commercial end-use applications. As many of these represent new and exciting areas, conventional mechanical property data, such as hardness and static tensile testing no longer suffice and a heightened need for advanced mechanical property data has frequently emerged.  With this in mind, and your stature as a prolific researcher in this field, I cordially invite you to submit an original manuscript on advanced mechanical testing of powder metallurgy materials to be published as part of a Special Issue in the journal Metals. Focal areas of interest include (but are not limited to) dynamic mechanical testing (fatigue, impact, fracture toughness, etc.), thermal mechanical testing, tribological testing, impulse excitation testing, and elevated temperature testing accompanied by microstructural and/or thermal analyses so as to instill a comprehensive understanding of the observed mechanical behaviour. Ferrous and non-ferrous alloys are both of interest, as well as metal matrix composites made thereof.

Prof. Dr. Paul Bishop
Guest Editor

Manuscript Submission Information

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Keywords

  • Powder Metallurgy Alloys
  • Advanced Mechanical Testing
  • Material Characterization
  • Ferrous alloys
  • Non-ferrous Alloys

Published Papers (5 papers)

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Research

18 pages, 4306 KiB  
Article
Thermal Mechanical Processing of Press and Sinter Al-Cu-Mg-Sn-(AlN) Metal Matrix Composite Materials
by Gregory A. W. Sweet, Mary A. Wells, Alan Taylor, Richard L. Hexemer, Ian W. Donaldson and Donald Paul Bishop
Metals 2018, 8(7), 480; https://doi.org/10.3390/met8070480 - 23 Jun 2018
Cited by 7 | Viewed by 3523
Abstract
The forging of sintered aluminum powder metallurgy alloys is currently viewed as a promising industrial technology for the manufacture of complex engineered products. The powder metallurgy process facilitates the use of admixed ceramic particles to produce aluminum metal matrix composites. However, fundamental data [...] Read more.
The forging of sintered aluminum powder metallurgy alloys is currently viewed as a promising industrial technology for the manufacture of complex engineered products. The powder metallurgy process facilitates the use of admixed ceramic particles to produce aluminum metal matrix composites. However, fundamental data on the thermal-mechanical response of commercially relevant powder metallurgy alloy systems under varying conditions of temperature and strain rate are lacking. To address this constraint, the current study investigates the thermal-mechanical processing response of a family of metal matrix composite materials that employ a commercially exploited base alloy system coupled with admixed additions of aluminum nitride. Industrially-sintered compacts were tested under hot compression using a Gleeble 3500 thermal-mechanical test system to quantify their flow behavior. The nominal workability was assessed as a function of material formulation, sintered preform condition, and processing parameters (temperature and strain rate). Optical metallography and electron backscatter diffraction were used to observe the grain evolution through deformation. Full densification was achieved for materials with ceramic concentrations of 2% volume or less. Zener-Hollomon constituent analyses were also completed to elucidate a more comprehensive understanding the flow behavior inherent to each material. Flow behavior varied directly with the sintered density, which was influenced by the concentration and nature of ceramic particulate. Full article
(This article belongs to the Special Issue Advanced Mechanical Testing of Powder Metallurgy Alloys)
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12 pages, 6058 KiB  
Article
A Hot Extrusion Process without Sintering by Applying MWCNTs/Al6061 Composites
by Hyung Yoon Seo, Long Rui Jiang, Chung Gil Kang and Chul Kyu Jin
Metals 2018, 8(3), 184; https://doi.org/10.3390/met8030184 - 14 Mar 2018
Cited by 4 | Viewed by 3751
Abstract
For carbon nanotube (CNT)/Al composites, compaction forming is conducted for densification processing, and then sintering and secondary processes are conducted. This general process has problems such as the complexity of the processing procedures, and high manufacturing costs. This study presents a hot extrusion [...] Read more.
For carbon nanotube (CNT)/Al composites, compaction forming is conducted for densification processing, and then sintering and secondary processes are conducted. This general process has problems such as the complexity of the processing procedures, and high manufacturing costs. This study presents a hot extrusion process without sintering for fabrication of CNTs/Al6061 composites. Before hot extrusion, preforms are fabricated by the compaction process for the mixture of Al6061 power and CNTs. Several hot extrusion experiments were performed under six types of CNT content; three extrusion ratios and three extrusion temperatures. The formability increased as the extrusion temperature increased for low CNT content. At 620 °C, the forming of all materials except for 10 vol % CNTs/Al6061 was possible at extrusion ratios R = 4, R = 8, and R = 16. As CNT content increases, extrusion pressure almost linearly increases. As the extrusion ratio increases, the extrusion pressure increases. The amount of CNT content increases as Vickers hardness increases. The Vicker’s hardness of 1 vol % CNTs/Al6061 billet is about 100 HV while that of 10 vol % CNTs/Al6061 billet is about 230 HV. There are no significant differences of compression stress according to extrusion ratio as observed in terms of pure Al6061, 1 vol % CNT/Al6061, and 3 vol % CNTs/Al6061. Full article
(This article belongs to the Special Issue Advanced Mechanical Testing of Powder Metallurgy Alloys)
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8041 KiB  
Article
Dependence of Creep Performance and Microstructure Evolution on Solution Cooling Rate in a Polycrystalline Superalloy
by Chao Xu, Feng Liu, Lan Huang and Liang Jiang
Metals 2018, 8(1), 4; https://doi.org/10.3390/met8010004 - 22 Dec 2017
Cited by 11 | Viewed by 4208
Abstract
It is well known that the solution cooling rate has a great effect on the creep life of superalloys. In this research, three typical cooling rates were applied to generate different distributions of γ’ precipitates for creep tests. Ingots used to make specimens [...] Read more.
It is well known that the solution cooling rate has a great effect on the creep life of superalloys. In this research, three typical cooling rates were applied to generate different distributions of γ’ precipitates for creep tests. Ingots used to make specimens were manufactured by hot extrusion, and the master alloy had the composition of an FGH4096 power metallurgy superalloy. SEM and SESD were used to observe the microstructure’s evolution. The experimental results show that the fastest cooling rate corresponds to the highest creep life as well as the smallest rupture strain, and vice versa. The microscopic observations disclose that with an increasing cooling rate, the size and area fraction of γ’ precipitates decrease, and the rupture mechanism changes from transgranular to intergranular. Moreover, some γ’ precipitates changed to cuboid after the creep test. The results will provide new technological processes to design more creep-resistant, nickel-base superalloys. Full article
(This article belongs to the Special Issue Advanced Mechanical Testing of Powder Metallurgy Alloys)
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9552 KiB  
Article
Effect of Compression Process of MWCNT-Reinforced Al6061 Powder on Densification Characteristics and Its Mechanical Properties
by Hyung Yoon Seo, Long Rui Jiang, Chung Gil Kang and Chul Kyu Jin
Metals 2017, 7(10), 437; https://doi.org/10.3390/met7100437 - 18 Oct 2017
Cited by 10 | Viewed by 4101
Abstract
In this paper, aluminium-based (Al6061) composites with 1, 3, 5, 7, and 10 vol % of multi-walled carbon nanotubes (MWCNTs) are investigated. The composites are fabricated by high-energy ball milling, cold-compacting at room temperature under compacting pressures of 400–1600 MPa, and sintering at [...] Read more.
In this paper, aluminium-based (Al6061) composites with 1, 3, 5, 7, and 10 vol % of multi-walled carbon nanotubes (MWCNTs) are investigated. The composites are fabricated by high-energy ball milling, cold-compacting at room temperature under compacting pressures of 400–1600 MPa, and sintering at 620 °C in an argon gas atmosphere. Thereafter, the hardness and microstructure of MWCNTs/Al6061 composites are examined. Further, to improve the relative density and hardness level of the complex material, open-die forging is performed after cold-compacting under 1 GPa pressure at room temperature and sintering at 620 °C. The open-die forging parameters include 1, 3, 5, 7, and 10 vol % MWCNTs/Al6061, and Al6061. The experimental results show that the mechanical properties of the composites are significantly superior to that of the Al6061 alloy after undergoing cold-compacting, sintering, and open-die forging. Full article
(This article belongs to the Special Issue Advanced Mechanical Testing of Powder Metallurgy Alloys)
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6551 KiB  
Article
Effects of Post-Sinter Processing on an Al–Zn–Mg–Cu Powder Metallurgy Alloy
by Matthew David Harding, Ian William Donaldson, Rich Lester Hexemer Junior and Donald Paul Bishop
Metals 2017, 7(9), 370; https://doi.org/10.3390/met7090370 - 13 Sep 2017
Cited by 7 | Viewed by 4500
Abstract
The objective of this work was to study the effects of several post-sinter processing operations (heat-treatment, sizing, shot peening) on a press-and-sinter 7xxx series aluminum powder metallurgy (PM) alloy. The characterization of the products was completed through a combination of non-contact surface profiling, [...] Read more.
The objective of this work was to study the effects of several post-sinter processing operations (heat-treatment, sizing, shot peening) on a press-and-sinter 7xxx series aluminum powder metallurgy (PM) alloy. The characterization of the products was completed through a combination of non-contact surface profiling, hardness measurements, differential scanning calorimetry (DSC), transmission electron microscopy (TEM), X-ray diffraction (XRD), tensile, and three-point bend fatigue testing. It was determined that sizing in the as-quenched state imparted appreciable reductions in surface hardness (78 HRB) and fatigue strength (168 MPa) relative to counterpart specimens that were sized prior to solutionizing (85 HRB and 228 MPa). These declines in performance were ascribed to the annihilation of quenched in vacancies that subsequently altered the nature of precipitates within the finished product. The system responded well to shot peening, as this process increased fatigue strength to 294 MPa. However, thermal exposure at 353 K (80 °C) and 433 K (160 °C) then reduced fatigue performance to 260 MPa and 173 MPa, respectively, as a result of residual stress relaxation and in-situ over-aging. Full article
(This article belongs to the Special Issue Advanced Mechanical Testing of Powder Metallurgy Alloys)
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