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3951 KiB

Open AccessArticle

Evaluation of Subsequent Heat Treatment Routes for Near-β Forged TA15 Ti-Alloy

by Zhichao Sun, Huili Wu and He Yang

Materials 2016, 9(11), 872; https://doi.org/10.3390/ma9110872 - 26 Oct 2016

Cited by 2 | Viewed by 4194

Abstract

TA15 Ti-alloy is widely used to form key load-bearing components in the aerospace field, where excellent service performance is needed. Near-β forging technology provides an attractive way to form these complicated Ti-alloy components but subsequent heat treatment has a great impact on the [...] Read more.

TA15 Ti-alloy is widely used to form key load-bearing components in the aerospace field, where excellent service performance is needed. Near-β forging technology provides an attractive way to form these complicated Ti-alloy components but subsequent heat treatment has a great impact on the final microstructure and mechanical properties. Therefore evaluation and determination of the heat treatment route is of particular significance. In this paper, for the near-β forged TA15 alloy, the formation and evolution of microstructures under different subsequent heat treatment routes (annealing, solution and aging, toughening and strengthening) were studied and the cooling mode after forging was also considered. Then, the type and characteristics of the obtained microstructures were discussed through quantitative metallographic analysis. The corresponding mechanical properties (tensile, impact toughness, and fracture toughness) and effects of microstructural characteristics were investigated. Finally, for a required microstructure and performance a reasonable heat treatment route was recommended. The work is of importance for the application and development of near-β forging technology. Full article

(This article belongs to the Special Issue Physical Metallurgy of High Performance Alloys)

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7109 KiB

Open AccessArticle

Grain Refinement Efficiency in Commercial-Purity Aluminum Influenced by the Addition of Al-4Ti Master Alloys with Varying TiAl₃ Particles

by Jianhua Zhao, Jiansheng He, Qi Tang, Tao Wang and Jing Chen

Materials 2016, 9(11), 869; https://doi.org/10.3390/ma9110869 - 26 Oct 2016

Cited by 10 | Viewed by 4459

Abstract

A series of Al-4Ti master alloys with various TiAl₃ particles were prepared via pouring the pure aluminum added with K₂TiF₆ or sponge titanium into three different molds made of graphite, copper, and sand. The microstructure and morphology of TiAl [...] Read more.

A series of Al-4Ti master alloys with various TiAl₃ particles were prepared via pouring the pure aluminum added with K₂TiF₆ or sponge titanium into three different molds made of graphite, copper, and sand. The microstructure and morphology of TiAl₃ particles were characterized and analyzed by scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). The microstructure of TiAl₃ particles in Al-4Ti master alloys and their grain refinement efficiency in commercial-purity aluminum were investigated in this study. Results show that there were three different morphologies of TiAl₃ particles in Al-4Ti master alloys: petal-like structures, blocky structures, and flaky structures. The Al-4Ti master alloy with blocky TiAl₃ particles had better and more stable grain refinement efficiency than the master alloys with petal-like and flaky TiAl₃ particles. The average grain size of the refined commercial-purity aluminum always hereditarily followed the size of the original TiAl₃ particles. In addition, the grain refinement efficiency of Al-4Ti master alloys with the same morphology, size, and distribution of TiAl₃ particles prepared through different processes was almost identical. Full article

(This article belongs to the Special Issue Physical Metallurgy of High Performance Alloys)

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8838 KiB

Open AccessArticle

Microstructure Evolution of HSLA Pipeline Steels after Hot Uniaxial Compression

by Yongchang Liu, Yi Shao, Chenxi Liu, Yan Chen and Dantian Zhang

Materials 2016, 9(9), 721; https://doi.org/10.3390/ma9090721 - 24 Aug 2016

Cited by 10 | Viewed by 3994

Abstract

The mechanical properties of the high-strength low-alloy pipeline steels were mainly controlled by the subsequent phase transformations after rolling. The influence of hot uniaxial compression on the phase transformation of acicular ferrite was explored by viewing of the deformation degree, the deformation temperature, [...] Read more.

The mechanical properties of the high-strength low-alloy pipeline steels were mainly controlled by the subsequent phase transformations after rolling. The influence of hot uniaxial compression on the phase transformation of acicular ferrite was explored by viewing of the deformation degree, the deformation temperature, and the strain rate. The results show that the increase of deformation amounts raises the transformation starting and finishing temperature during the subsequent cooling and also promotes the polygonal ferrite transformation, which leads to the decrease of Vickers hardness accordingly. With the increasing of the deformation temperature, the achieved microstructure becomes coarsened and thus decreases the hardness. As the strain rate increases, the microstructure is refined and thus the hardness increases gradually; increasing the strain rate appropriately is beneficial to the refinement of the microstructure. Full article

(This article belongs to the Special Issue Physical Metallurgy of High Performance Alloys)

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4386 KiB

Open AccessArticle

Tailorable Burning Behavior of Ti14 Alloy by Controlling Semi-Solid Forging Temperature

by Yongnan Chen, Wenqing Yang, Haifei Zhan, Fengying Zhang, Yazhou Huo, Yongqing Zhao, Xuding Song and Yuantong Gu

Materials 2016, 9(8), 697; https://doi.org/10.3390/ma9080697 - 16 Aug 2016

Cited by 11 | Viewed by 5157

Abstract

Semi-solid processing (SSP) is a popular near-net-shape forming technology for metals, while its application is still limited in titanium alloy mainly due to its low formability. Recent works showed that SSP could effectively enhance the formability and mechanical properties of titanium alloys. The [...] Read more.

Semi-solid processing (SSP) is a popular near-net-shape forming technology for metals, while its application is still limited in titanium alloy mainly due to its low formability. Recent works showed that SSP could effectively enhance the formability and mechanical properties of titanium alloys. The processing parameters such as temperature and forging rate/ratio, are directly correlated with the microstructure, which endow the alloy with different chemical and physical properties. Specifically, as a key structural material for the advanced aero-engine, the burn resistant performance is a crucial requirement for the burn resistant titanium alloy. Thus, this work aims to assess the burning behavior of Ti14, a kind of burn resistant alloy, as forged at different semi-solid forging temperatures. The burning characteristics of the alloy are analyzed by a series of burning tests with different burning durations, velocities, and microstructures of burned sample. The results showed that the burning process is highly dependent on the forging temperature, due to the fact that higher temperatures would result in more Ti₂Cu precipitate within grain and along grain boundaries. Such a microstructure hinders the transport of oxygen in the stable burning stage through the formation of a kind of oxygen isolation Cu-enriched layer under the burn product zone. This work suggests that the burning resistance of the alloy can be effectively tuned by controlling the temperature during the semi-solid forging process. Full article

(This article belongs to the Special Issue Physical Metallurgy of High Performance Alloys)

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3730 KiB

Open AccessArticle

Effects of Rapid Thermal Annealing on the Structural, Electrical, and Optical Properties of Zr-Doped ZnO Thin Films Grown by Atomic Layer Deposition

by Jingjin Wu, Yinchao Zhao, Ce Zhou Zhao, Li Yang, Qifeng Lu, Qian Zhang, Jeremy Smith and Yongming Zhao

Materials 2016, 9(8), 695; https://doi.org/10.3390/ma9080695 - 13 Aug 2016

Cited by 19 | Viewed by 7193

Abstract

The 4 at. % zirconium-doped zinc oxide (ZnO:Zr) films grown by atomic layer deposition (ALD) were annealed at various temperatures ranging from 350 to 950 °C. The structural, electrical, and optical properties of rapid thermal annealing (RTA) treated ZnO:Zr films have been evaluated [...] Read more.

The 4 at. % zirconium-doped zinc oxide (ZnO:Zr) films grown by atomic layer deposition (ALD) were annealed at various temperatures ranging from 350 to 950 °C. The structural, electrical, and optical properties of rapid thermal annealing (RTA) treated ZnO:Zr films have been evaluated to find out the stability limit. It was found that the grain size increased at 350 °C and decreased between 350 and 850 °C, while creeping up again at 850 °C. UV–vis characterization shows that the optical band gap shifts towards larger wavelengths. The Hall measurement shows that the resistivity almost keeps constant at low annealing temperatures, and increases rapidly after treatment at 750 °C due to the effect of both the carrier concentration and the Hall mobility. The best annealing temperature is found in the range of 350–550 °C. The ZnO:Zr film-coated glass substrates show good optical and electrical performance up to 550 °C during superstrate thin film solar cell deposition. Full article

(This article belongs to the Special Issue Physical Metallurgy of High Performance Alloys)

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8739 KiB

Open AccessArticle

Comparison of Ductile-to-Brittle Transition Behavior in Two Similar Ferritic Oxide Dispersion Strengthened Alloys

by Jesus Chao, Rosalia Rementeria, Maria Aranda, Carlos Capdevila and Jose Luis Gonzalez-Carrasco

Materials 2016, 9(8), 637; https://doi.org/10.3390/ma9080637 - 29 Jul 2016

Cited by 14 | Viewed by 6728

Abstract

The ductile-to-brittle transition (DBT) behavior of two similar Fe-Cr-Al oxide dispersion strengthened (ODS) stainless steels was analyzed following the Cottrell–Petch model. Both alloys were manufactured by mechanical alloying (MA) but by different forming routes. One was manufactured as hot rolled tube, and the [...] Read more.

The ductile-to-brittle transition (DBT) behavior of two similar Fe-Cr-Al oxide dispersion strengthened (ODS) stainless steels was analyzed following the Cottrell–Petch model. Both alloys were manufactured by mechanical alloying (MA) but by different forming routes. One was manufactured as hot rolled tube, and the other in the form of hot extruded bar. The two hot forming routes considered do not significantly influence the microstructure, but cause differences in the texture and the distribution of oxide particles. These have little influence on tensile properties; however, the DBT temperature and the upper shelf energy (USE) are significantly affected because of delamination orientation with regard to the notch plane. Whereas in hot rolled material the delaminations are parallel to the rolling surface, in the hot extruded material, they are randomly oriented because the material is transversally isotropic. Full article

(This article belongs to the Special Issue Physical Metallurgy of High Performance Alloys)

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6318 KiB

Open AccessArticle

Enhanced Thermoelectric Performance of Cu₂SnSe₃-Based Composites Incorporated with Nano-Fullerene

by Degang Zhao, Jiai Ning, Di Wu and Min Zuo

Materials 2016, 9(8), 629; https://doi.org/10.3390/ma9080629 - 28 Jul 2016

Cited by 14 | Viewed by 5122

Abstract

In this study, nano-sized fullerene C₆₀ powder was sufficiently mixed with Cu₂SnSe₃ powder by ball milling method, and the C₆₀/Cu₂SnSe₃ composites were prepared by spark plasma sintering technology. The fullerene C₆₀ distributed uniformly [...] Read more.

In this study, nano-sized fullerene C₆₀ powder was sufficiently mixed with Cu₂SnSe₃ powder by ball milling method, and the C₆₀/Cu₂SnSe₃ composites were prepared by spark plasma sintering technology. The fullerene C₆₀ distributed uniformly in the form of clusters, and the average cluster size was less than 1 μm. With increasing C₆₀ content, the electrical conductivity of C₆₀/Cu₂SnSe₃ composites decreased, while the Seebeck coefficient was enhanced. The thermal conductivity of composites decreased significantly, which resulted from the phonon scattering by the C₆₀ clusters located on the grain boundaries of the Cu₂SnSe₃ matrix. The highest figure of merit ZT of 0.38 was achieved at 700 K for 0.8% C₆₀/Cu₂SnSe₃ composite. Full article

(This article belongs to the Special Issue Physical Metallurgy of High Performance Alloys)

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Review

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9606 KiB

Open AccessReview

Advancement of Compositional and Microstructural Design of Intermetallic γ-TiAl Based Alloys Determined by Atom Probe Tomography

by Thomas Klein, Helmut Clemens and Svea Mayer

Materials 2016, 9(9), 755; https://doi.org/10.3390/ma9090755 - 6 Sep 2016

Cited by 44 | Viewed by 6818

Abstract

Advanced intermetallic alloys based on the γ-TiAl phase have become widely regarded as most promising candidates to replace heavier Ni-base superalloys as materials for high-temperature structural components, due to their facilitating properties of high creep and oxidation resistance in combination with a low [...] Read more.

Advanced intermetallic alloys based on the γ-TiAl phase have become widely regarded as most promising candidates to replace heavier Ni-base superalloys as materials for high-temperature structural components, due to their facilitating properties of high creep and oxidation resistance in combination with a low density. Particularly, recently developed alloying concepts based on a β-solidification pathway, such as the so-called TNM alloy, which are already incorporated in aircraft engines, have emerged offering the advantage of being processible using near-conventional methods and the option to attain balanced mechanical properties via subsequent heat-treatment. Development trends for the improvement of alloying concepts, especially dealing with issues regarding alloying element distribution, nano-scale phase characterization, phase stability, and phase formation mechanisms demand the utilization of high-resolution techniques, mainly due to the multi-phase nature of advanced TiAl alloys. Atom probe tomography (APT) offers unique possibilities of characterizing chemical compositions with a high spatial resolution and has, therefore, been widely used in recent years with the aim of understanding the materials constitution and appearing basic phenomena on the atomic scale and applying these findings to alloy development. This review, thus, aims at summarizing scientific works regarding the application of atom probe tomography towards the understanding and further development of intermetallic TiAl alloys. Full article

(This article belongs to the Special Issue Physical Metallurgy of High Performance Alloys)

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