Editorial

127 KiB

Open AccessEditorial

by Anders E.W. Jarfors

Metals 2016, 6(1), 15; https://doi.org/10.3390/met6010015 - 08 Jan 2016

Cited by 2 | Viewed by 2835

Castings and the cast metals are among the most important facets creating a foundation for modern life. [...] Full article

(This article belongs to the Special Issue Casting Alloy Design and Modification)

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1707 KiB

Open AccessArticle

Effect of Post Heat Treatment on the Microstructure and Microhardness of Friction Stir Processed NiAl Bronze (NAB) Alloy

by Yuting Lv, Liqiang Wang, Xiaoyan Xu and Weijie Lu

Metals 2015, 5(3), 1695-1703; https://doi.org/10.3390/met5031695 - 16 Sep 2015

Cited by 26 | Viewed by 6145

Abstract

NiAl bronze (NAB) alloy is prepared by using friction stir processing (FSP) technique at a tool rotation rate of 1200 rpm and a traverse speed of 150 mm/min. A post heat treatment is performed at the temperature of 675 °C. The effect of [...] Read more.

NiAl bronze (NAB) alloy is prepared by using friction stir processing (FSP) technique at a tool rotation rate of 1200 rpm and a traverse speed of 150 mm/min. A post heat treatment is performed at the temperature of 675 °C. The effect of heat treatment on the microstructure and microhardness is studied. The results show that the microstructure of the FSP NAB alloy consists of high density dislocations, retained β phase (β′ phase) and recrystallized grains. When annealed at 675 °C, discontinuous static recrystallization (DSRX) takes place. The content of β′ phase gradually decreases and fine κ phase is precipitated. After annealing for 2 h, both the microhardness of the FSP sample in the stir zone (SZ) and the difference in hardness between the SZ and base metal decrease due to the reduction of the dislocation density and β′ phase, accompanying recrystallized grain coarsening. With further increasing of the annealing time to 4 h, the aforementioned difference in hardness nearly disappears. Full article

(This article belongs to the Special Issue Casting Alloy Design and Modification)

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1140 KiB

Open AccessArticle

Effect of Material and Process Atmosphere in the Preparation of Al-Ti-B Grain Refiner by SHS

by Iban Vicario, Angeline Poulon-Quintin, Miguel Angel Lagos and Jean-François Silvain

Metals 2015, 5(3), 1387-1396; https://doi.org/10.3390/met5031387 - 30 Jul 2015

Cited by 11 | Viewed by 5594

Abstract

Al-Ti-B master alloys are widely used in the aluminum industry as grain refiners for the control of the microstructure of the aluminum alloys. The SHS (self-propagating high-temperature synthesis) is an ex situ method that uses exothermic reactions to sustain the chemical reaction in [...] Read more.

Al-Ti-B master alloys are widely used in the aluminum industry as grain refiners for the control of the microstructure of the aluminum alloys. The SHS (self-propagating high-temperature synthesis) is an ex situ method that uses exothermic reactions to sustain the chemical reaction in a combustion wave. The advantages of SHS are the low energy requirement, simplicity and product purity. However, the raw material used has to be very pure, with a very small size leading to the necessity of a reactor with a protective gas to produce the reaction. The purpose of this investigation is to fabricate SHS master alloys with commercial standard raw materials, with lower purity and higher grain size without a reactor or protective gas in order to (1) decrease the price and (2) improve the productivity of master alloy manufacturing. The possibility of using cheap borated salts instead of expensive pure boron has been studied. Different compositions of aluminum master alloy have been developed. Bigger TiB₂ grain size has been obtained when using bigger commercial raw materials. Larger titanium powder can produce an aluminum master alloy with a maximum of 30% of aluminum without reactor. In comparison, SHS reaction is much more difficult when using finer titanium powder. Full article

(This article belongs to the Special Issue Casting Alloy Design and Modification)

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1723 KiB

Open AccessArticle

On Thermal Expansion and Density of CGI and SGI Cast Irons

by Taishi Matsushita, Ehsan Ghassemali, Albano Gómez Saro, Lennart Elmquist and Anders E. W. Jarfors

Metals 2015, 5(2), 1000-1019; https://doi.org/10.3390/met5021000 - 04 Jun 2015

Cited by 21 | Viewed by 7385

Abstract

The thermal expansion and density of Compacted Graphite Iron (CGI) and Spheroidal Graphite Iron (SGI) were measured in the temperature range of 25–500 °C using push-rod type dilatometer. The coefficient of the thermal expansion (CTE) of cast iron can be expressed by the [...] Read more.

The thermal expansion and density of Compacted Graphite Iron (CGI) and Spheroidal Graphite Iron (SGI) were measured in the temperature range of 25–500 °C using push-rod type dilatometer. The coefficient of the thermal expansion (CTE) of cast iron can be expressed by the following equation: CTE = 1.38 × 10⁻⁵ + 5.38 × 10⁻⁸ N − 5.85 × 10⁻⁷ G + 1.85 × 10⁻⁸ T − 2.41 × 10⁻⁶ R_P/F − 1.28 × 10⁻⁸ NG − 2.97 × 10⁻⁷ GR_P/F + 4.65 × 10⁻⁹ TR_P/F + 1.08 × 10⁻⁷ G² − 4.80 × 10⁻¹¹ T² (N: Nodularity, G: Area fraction of graphite (%), T: Temperature (°C), R_P/F: Pearlite/Ferrite ratio in the matrix). Full article

(This article belongs to the Special Issue Casting Alloy Design and Modification)

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1377 KiB

Open AccessArticle

Integral Steel Casting of Full Spade Rudder Trunk Carrier Housing for Supersized Container Vessels through Casting Process Engineering (Sekjin E&T)

by Tae Won Kim, Chul Kyu Jin, Ill Kab Jeong, Sang Sub Lim, Jea Chul Mun, Chung Gil Kang, Hyung Yoon Seo and Jong Deok Kim

Metals 2015, 5(2), 706-719; https://doi.org/10.3390/met5020706 - 30 Apr 2015

Cited by 5 | Viewed by 8247

Abstract

In casting steel for offshore construction, integral casted structures are superior to welded structures in terms of preventing fatigue cracks in the stress raisers. In this study, mold design and casting analysis were conducted for integral carrier housing. Casting simulation was used for [...] Read more.

In casting steel for offshore construction, integral casted structures are superior to welded structures in terms of preventing fatigue cracks in the stress raisers. In this study, mold design and casting analysis were conducted for integral carrier housing. Casting simulation was used for predicting molten metal flow and solidification during carrier housing casting, as well as the hot spots and porosity of the designed runner, risers, riser laggings, and the chiller. These predictions were used for deriving the final carrier housing casting plan, and a prototype was fabricated accordingly. A chemical composition analysis was conducted using a specimen sampled from a section of the prototype; the analytically obtained chemical composition agreed with the chemical composition of the existing carrier housing. Tensile and Charpy impact tests were conducted for determining the mechanical material properties. Carrier housing product after normalizing (920 °C/4.5 h, air-cooling) has 371 MPa of yield strength, 582 MPa of tensile strength, 33.4% of elongation as well as 64 J (0 °C) of impact energy. Full article

(This article belongs to the Special Issue Casting Alloy Design and Modification)

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769 KiB

Open AccessCommunication

Effects of Different Heat Treatment on Microstructure, Mechanical and Conductive Properties of Continuous Rheo-Extruded Al-0.9Si-0.6Mg (wt%) Alloy

by Di Tie, Ren-guo Guan, Ning Guo, Zhouyang Zhao, Ning Su, Jing Li and Yang Zhang

Metals 2015, 5(2), 648-655; https://doi.org/10.3390/met5020648 - 21 Apr 2015

Cited by 10 | Viewed by 6318

Abstract

Al-0.9Si-0.6Mg (wt%) alloy conductive wires were designed and produced by continuous rheo-extrusion process. The effects of different heat treatment on microstructure, mechanical and conductive properties of the wires were studied. Results show that, after T6 heat treatment, conductive property of the alloy increased [...] Read more.

Al-0.9Si-0.6Mg (wt%) alloy conductive wires were designed and produced by continuous rheo-extrusion process. The effects of different heat treatment on microstructure, mechanical and conductive properties of the wires were studied. Results show that, after T6 heat treatment, conductive property of the alloy increased while elongation decreased with the higher aging temperature and longer aging time. After T8 and T9 heat treatment, acicular strengthening phase β''-Mg₂Si homogeneously precipitated, which effectively improved mechanical and conductive property of the alloy. The tensile strength, elongation and resistivity of T8 heat treated alloy reached 336 MPa, 13.7% and 29.3 nΩm respectively. After T9 heat treatment, the alloy’s tensile strength, elongation and resistivity was 338 MPa, 6.0% and 30.2 nΩ·m respectively. Full article

(This article belongs to the Special Issue Casting Alloy Design and Modification)

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4745 KiB

Open AccessArticle

Research on Semisolid Microstructural Evolution of 2024 Aluminum Alloy Prepared by Powder Thixoforming

by Pubo Li, Tijun Chen, Suqing Zhang and Renguo Guan

Metals 2015, 5(2), 547-564; https://doi.org/10.3390/met5020547 - 03 Apr 2015

Cited by 32 | Viewed by 8745

Abstract

A novel method, powder thixoforming, for net-shape forming of the particle-reinforced Aluminum matrix composites in semi-solid state has been proposed based on powder metallurgy combining with thixoforming technology. The microstructural evolution and phase transformations have been investigated during partial remelting of the 2024 [...] Read more.

A novel method, powder thixoforming, for net-shape forming of the particle-reinforced Aluminum matrix composites in semi-solid state has been proposed based on powder metallurgy combining with thixoforming technology. The microstructural evolution and phase transformations have been investigated during partial remelting of the 2024 bulk alloy, prepared by cold pressing of atomized alloy powders to clarify the mechanisms of how the consolidated powders evolve into small and spheroidal primary particles available for thixoforming. The effect of heating temperature on the resulting semisolid microstructure has also been discussed. The results indicate that the microstructural evolution includes three stages—the initial rapid coarsening of the fine grains within the powders, the formation of continuous liquid layer on the primary particle surface (the original powder), and the final coarsening—that result from the phase transformations of θ→α, α→L, and α→L and L→α, respectively. The coarsening rate of the primary particles is low, and one original powder always evolves into one spheroidal particle with a continuous liquid layer surface. Properly raising the heating temperature is beneficial for obtaining an ideal semisolid microstructure. Full article

(This article belongs to the Special Issue Casting Alloy Design and Modification)

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1989 KiB

Open AccessArticle

A Comparative Characterization of the Microstructures and Tensile Properties of As-Cast and Thixoforged in situ AM60B-10 vol% Mg₂Si_p Composite and Thixoforged AM60B

by Suqing Zhang, Tijun Chen, Faliang Cheng and Pubo Li

Metals 2015, 5(1), 457-470; https://doi.org/10.3390/met5010457 - 13 Mar 2015

Cited by 18 | Viewed by 5324

Abstract

The microstructure and tensile properties of the thixoforged in situ Mg₂Si_p/AM60B composite were characterized in comparison with the as-cast composite and thixoforged AM60B. The results indicate that the morphology of α-Mg phases, the distribution and amount of β phases [...] Read more.

The microstructure and tensile properties of the thixoforged in situ Mg₂Si_p/AM60B composite were characterized in comparison with the as-cast composite and thixoforged AM60B. The results indicate that the morphology of α-Mg phases, the distribution and amount of β phases and the distribution and morphology of Mg₂Si particles in thixoforged composite are completely different from those in as-cast composite. The Mg₂Si particles block heat transfer and prevent the α-Mg particles from rotation or migration during reheating. Both the thixoforged composite and thixoforged AM60B alloy exhibit virtually no porosity in the microstructure. The thixoforged composite has the highest comprehensive tensile properties (ultimate tensile strength (UTS)) of 209 MPa and an elongation of 10.2%. The strengthening mechanism of the Mg₂Si particle is the additive or synergetic effect of combining the load transfer mechanism, the Orowan looping mechanism and the dislocation strengthening mechanism. Among them, the load transfer mechanism is the main mechanism, and the latter two are minor. The particle splitting and interfacial debonding are the main damage patterns of the composite. Full article

(This article belongs to the Special Issue Casting Alloy Design and Modification)

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1779 KiB

Open AccessArticle

Effects of Rare Earth on the Microstructure and Impact Toughness of H13 Steel

by Jinzhu Gao, Paixian Fu, Hongwei Liu and Dianzhong Li

Metals 2015, 5(1), 383-394; https://doi.org/10.3390/met5010383 - 11 Mar 2015

Cited by 106 | Viewed by 9223

Abstract

Studies of H13 steel suggest that under appropriate conditions, additions of rare-earth metals (REM) can significantly enhance mechanical properties, such as impact toughness. This improvement is apparently due to the formation of finer and more dispersive RE inclusions and grain refinement after REM [...] Read more.

Studies of H13 steel suggest that under appropriate conditions, additions of rare-earth metals (REM) can significantly enhance mechanical properties, such as impact toughness. This improvement is apparently due to the formation of finer and more dispersive RE inclusions and grain refinement after REM additions. In this present work, the microstructure evolution and mechanical properties of H13 steel with rare earth additions (0, 0.015, 0.025 and 0.1 wt.%) were investigated. The grain size, inclusions and fracture morphology were systematically studied by means of optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that REM addition of 0.015 wt.% can result in good improvement of performance compared to the REM additions of 0.025 wt.% and 0.1 wt.%. It is found that the impact toughness is significantly enhanced with the addition of 0.015% REM, which can be improved 90% from 10 J to 19 J. Such an addition of REM can result in a huge volume fraction of finer and more dispersive inclusions which are extremely good to toughness. Full article

(This article belongs to the Special Issue Casting Alloy Design and Modification)

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1901 KiB

Open AccessArticle

Vacuum Die Casting Process and Simulation for Manufacturing 0.8 mm-Thick Aluminum Plate with Four Maze Shapes

by Chul Kyu Jin, Chang Hyun Jang and Chung Gil Kang

Metals 2015, 5(1), 192-205; https://doi.org/10.3390/met5010192 - 04 Feb 2015

Cited by 14 | Viewed by 10757

Abstract

Using vacuum die casting, 0.8 mm-thick plates in complicated shapes are manufactured with the highly castable aluminum alloy Silafont-36 (AlSi9MgMn). The sizes and shapes of the cavities, made of thin plates, feature four different mazes. To investigate formability and mechanical properties by shot [...] Read more.

Using vacuum die casting, 0.8 mm-thick plates in complicated shapes are manufactured with the highly castable aluminum alloy Silafont-36 (AlSi9MgMn). The sizes and shapes of the cavities, made of thin plates, feature four different mazes. To investigate formability and mechanical properties by shot condition, a total of six parameters (melt temperatures of 730 °C and 710 °C; plunger speeds of 3.0 m/s and 2.5 m/s; vacuum pressure of 250 mbar and no vacuum) are varied in experiments, and corresponding simulations are performed. Simulation results obtained through MAGMA software show similar tendencies to those of the experiments. When the melt pouring temperature is set to 730 °C rather than 710 °C, formability and mechanical properties are superior, and when the plunger speed is set to 3.0 m/s rather than to 2.5 m/s, a fine, even structure is obtained with better mechanical properties. The non-vacuumed sample is half unfilled. The tensile strength and elongation of the sample fabricated under a melt temperature of 730 °C, plunger speed of 3.0 m/s, and vacuum pressure of 250 mbar are 265 MPa and 8.5%, respectively. Full article

(This article belongs to the Special Issue Casting Alloy Design and Modification)

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