Effect of Direct Current on the Semi-Solid Isothermal Heat-Treated Microstructure of ZA84 Magnesium Alloy

2011 ◽  
Vol 189-193 ◽  
pp. 871-875
Author(s):  
Ming Bo Yang ◽  
Xiao Feng Liang ◽  
Yi Zhu
Keyword(s):  
Direct Current ◽  
Current Density ◽  
Dendritic Structure ◽  
Isothermal Treatment ◽  
Structure Evolution ◽  
Dendritic Microstructure ◽  
Experimental Conditions ◽  
Isothermal Temperature ◽  
Heat Treated ◽  
Semi Solid

The effect of direct current on the semi-solid isothermal heat-treated microstructure of ZA84 alloy is investigated. The results indicate that it is possible to produce ZA84 alloy with non-dendritic microstructure by semi-solid isothermal treatment. Furthermore, imposing direct current during the semi-solid isothermal treatment of ZA84 alloy can accelerate the non-dendritic structure evolution of the alloy. Under the experimental conditions of this work, higher the current density, quicker is the rate of non-dendritic structure evolution for the semi-solid isothermal heat-treated ZA84 alloy. Further investigations need to be considered in order to optimize the current density, isothermal temperature and holding time.

Comparison of Microstructure and Mechanical Properties of Semi-Solid Castings Produced Using Billets Made by EMS and SEED

2014 ◽  
Vol 217-218 ◽  
pp. 332-339 ◽  
Author(s):  
Xiao Kang Liang ◽  
Da Quan Li ◽  
Pascal Côté ◽  
Stephen P. Midson ◽  
Qiang Zhu
Keyword(s):  
Mechanical Properties ◽  
Cross Section ◽  
Dendritic Structure ◽  
Casting Process ◽  
Grain Structure ◽  
High Quality ◽  
Microstructure And Mechanical Properties ◽  
Grain Structures ◽  
Heat Treated ◽  
Semi Solid

The spheroidal grains in billets used for semi-solid casting are generally manufactured by electromagnetic stirring (EMS) during the casting process. This method however, is not economically applicable for small quantities of the thixo billets. Swirled Enthalpy Equilibration Device (SEED) has been developed as a rheocasting process, and the SEED process is of interest for developing new thixo alloys, as well as for optimizing the thixocasting processes for high quality components. The objective of this paper is to compare the microstructure and mechanical properties of aluminum alloy 319s billets and castings produced using EMS and SEED feed materials. The experimental results show that for as-cast billets made from SEED process, a well-developed spheroidal grain structure is distributed throughout the cross-section of the billet, while for as-cast EMS billets, the grain structure is inhomogeneous, i.e., a dendritic structure was present adjacent to the surface of the billet, while a uniform, spheroidal structure was present at the centre. After the thixocasting process, however, the both SEED and EMS billets have well-developed, spheroidal grain structures. Mechanical properties of thixocast and T61 heat treated components are comparable for the both SEED and EMS billets.

Compression Deformation Behavior of AZ91D Magnesium Alloy in Semi-Solid State

2007 ◽  
Vol 546-549 ◽  
pp. 151-154
Author(s):  
Ming Bo Yang ◽  
Fu Sheng Pan ◽  
Li Wen Tang ◽  
Hong Jun Hu
Keyword(s):  
Deformation Behavior ◽  
Deformation Rate ◽  
Deformation Temperature ◽  
Dendritic Structure ◽  
Isothermal Treatment ◽  
Compression Stress ◽  
Compression Strain ◽  
Compression Deformation ◽  
Maximum Compression Stress ◽  
Semi Solid

The semi-solid compression deformation behavior of the AZ91D alloy with non-dendritic structure, which was obtained under the semi-solid isothermal treatment condition of 570°C×60min, was studied by means of Gleeble-1500 thermal-mechanical simulator. When the compression strain was lower than 0.7, along with the compression strain increasing, the compression stress firstly increased rapidly, then decreased rapidly, and finally kept a constant stress level gradually. Under the condition of different deformation temperatures and deformation rates, the maximum compression stress was obtained simultaneously when the compression strain value was 0.025 approximatively. Furthermore, when the deformation rate kept a constant, the compression stress decreased along with the deformation temperature increasing, and when the deformation temperature kept a constant, the compression stress increased along with the deformation rate increasing.

Study of Microstructural Evolution and Phase’s Morphology after Partial Remelting in A356 Alloy

2008 ◽  
Vol 141-143 ◽  
pp. 367-372 ◽  
Author(s):  
A. Mahdavi ◽  
M. Bigdeli ◽  
M. Hajian Heidary ◽  
F. Khomamizadeh
Keyword(s):  
Dendritic Structure ◽  
A356 Alloy ◽  
Intermetallic Phases ◽  
Effective Parameters ◽  
Dendritic Microstructure ◽  
Globular Structure ◽  
Needle Morphology ◽  
Sima Process ◽  
Semi Solid ◽  
Globular Form

In this work, effective parameters of SIMA process to obtain non dendritic microstructure in A356 alloy were investigated. In addition, the effect of SIMA process on the evolution of morphology of silicon and intermetallic phases in this alloy was studied. Microstructure images obtained from optical microscopy and SEM observation showed that increase in plastic work up to 40% and then holding of samples in the semi solid state at temperature of 580oC, causes that primary dendritic structure changes to non dendritic, fine and globular structure, but optimum reheating time completely depended on initial thickness of samples. If all parameters of SIMA process are the same, the grain boundaries of thinner samples begin to wet and following globalization will be completed in shorter reheating time rather than thicker ones. Moreover, it was found that the intermetallic phases lost their angular or needle morphology and gradually changed to rounded morphology and even to globular form. Also the optimum reheating time thoroughly depends on primary casting microstructure as the finer casting microstructure begin to globalize faster than thicker one under more little stains.

Prepartion of Semisolid AM60 Alloy by Novel Self-Inoculation Method

2011 ◽  
Vol 189-193 ◽  
pp. 3804-3809 ◽  
Author(s):  
Yuan Dong Li ◽  
Bo Xing ◽  
Ying Ma ◽  
Ti Jun Chen ◽  
Yuan Hao
Keyword(s):  
Slope Angle ◽  
Dendritic Structure ◽  
Primary Phase ◽  
Chemical Pollution ◽  
Cooling Channel ◽  
Dendritic Microstructure ◽  
Pouring Temperature ◽  
Inoculation Method ◽  
Semi Solid ◽  
Slurry Preparation

A research focus on semi-solid metal processing is the preparation of semi-solid slurry with non-dendritic microstructure. During the past several decades, people tended to obtain the non-dendritic structure by stirring melt of alloy which downs to the semi-solid temperature range, such as mechanical stirring and electromagnetic stirring; In recent years, with the technological innovation of semi-solid slurry preparation turned to be more convenient and efficient, most of these processes are based on the control of nucleation and growth process of primary phase during solidification, such as NRC, SSR, SLC, SEED, and CRP. In this paper, a novel process, named as “Self-Inoculation Method (SIM)”, has been proposed for semi-solid slurry preparation. The process involves self-inoculants addition to the melt, and then pouring the melt to mould through a multi-stream mixed cooling channel. The melt was avoided chemical pollution due to the particles of self-inoculants from the same composition as the melt. The semi-solid billets of AM60 alloy with non-dendritic structure were prepared by SIM. The effects of process parameters on the microstructure and the mechanism on refinement of alloy were investigated. The results indicate that pouring temperature, addition amount of self-inoculants and slope angle of the cooling channel are key factors for SIM process. The optimized parameters for the billet preparation of AM60 alloy are obtained: pouring temperature is at 680°C~700°C；addition of self-inoculants are between 5%~7% (mass fraction)；slope angle of the cooling channel is at 30°~45°. The heterogeneous nucleation was enhanced as the addition of self-inoculants; the formation of chill crystal and the fragmentation of dendrites because of cooling and shearing of the cooling channel, resulting in the increase of grains density and a small grain size.

Comparison of Semisolid Microstructure Evolution of Wrought Nickel Based Superalloy GH4037 with Different Solid Fraction

2019 ◽  
Vol 285 ◽  
pp. 105-110
Author(s):  
Guan Fei Xiao ◽  
Ju Fu Jiang ◽  
Ying Wang ◽  
Ying Zhe Liu
Keyword(s):  
Solid Fraction ◽  
Microstructure Evolution ◽  
Isothermal Treatment ◽  
Liquid Droplets ◽  
Soaking Time ◽  
Isothermal Temperature ◽  
Nickel Based Superalloy ◽  
Temperature Ranges ◽  
Semi Solid ◽  
Average Size

The research on semisolid metal forming of Ni-based superalloys is limited because of the difficulties in preparing semisolid billets. Traditional methods for fabricating semisolid billets are SIMA and RAP. In order to decrease the processing procedures, a new method called semi-solid isothermal treatment of wrought superalloy (SSITWS) was used to fabricate semisolid billets in this paper. In order to get the optimal parameters to fabricate Ni-based GH4037 semisolid billets, the effects of isothermal temperature and soaking time on microstructure evolution were investigated. The isothermal temperature ranges from solidus to liquidus, and the soaking time ranges from 10min to 60min. The results show that near-globular grains can be obtained only in the semi-solid state with appropriate solid fractions. When the solid fraction was high, the shape of grains was irregular and the average size of grains was large and inhomogeneous. When the isothermal temperature reached 1350°C, spherical grains appeared, and many small intragranular liquid droplets existed. During the appropriate isothermal temperature range, from 1350°C to 1380°C, the shape of solid grains was globular and the size of solid grains was homogeneous. At the same time, the size of the grains and the roundness of the grains increased with the increasing of isothermal temperature.

Formation Mechanism of Thixotropic Microstructure of AM60 Alloy during Solidification

2014 ◽  
Vol 1030-1032 ◽  
pp. 86-89
Author(s):  
Bo Xing
Keyword(s):  
Formation Mechanism ◽  
Solid Substrate ◽  
Research Field ◽  
Primary Phase ◽  
Solid Particles ◽  
Metallographic Analysis ◽  
Semisolid Slurry ◽  
Dendritic Microstructure ◽  
Quenching Method ◽  
Semi Solid

A research field on semi-solid metal processing is the preparation of semi-solid slurry with non-dendritic microstructure. Nowadays, with the technological innovation of semi-solid slurry preparation, people turn to produce the non-dendritic semisolid microstructure by locally cooling of the alloy melt during solidification. Therefore, it is necessary to investigate the formation mechanism of the non-dendritic microstructure formation because the primary phase undergoes a specially controlled nucleation and growth which distinctly different from the commom solidification. In this paper, the semisolid slurry of AM60 alloy was produced by Self-Inoculation Method (SIM), and the microstructure evolution of primary α-Mg was investigated by water quenching method and metallographic analysis. The results indicate that the semisolid microstructure of AM60 alloy produced by SIM composed of small and globular α-Mg particles, and these grains undergone a coarsing process during quiescent holding. The solid substrate caused by the fusion of solid particles and the dendritic fragments caused by melt flow caused the grain multiplication, and then the grain undergone a steadily growth because of the uniform temperature distribution, resulting in the increase of grains density and a small grain size of the AM60 semisolid slurry.

Effects of T5 and T6 Heat Treatments Applied to Rheocast A356 Parts for Automotive Applications

2008 ◽  
Vol 141-143 ◽  
pp. 237-242 ◽  
Author(s):  
Mario Rosso ◽  
Ildiko Peter ◽  
R. Villa
Keyword(s):  
Fatigue Behaviour ◽  
Cyclic Stress ◽  
Industrial Applications ◽  
Fatigue Tests ◽  
Controlled Cooling ◽  
Test Analysis ◽  
Heat Treated ◽  
Mechanical Performances ◽  
Semi Solid ◽  
Number Of Cycles

The correlation between the evaluation of the mechanical and of the fatigue behaviour of the rheocast, T5 and T6 heat treated SSM A356 aluminium alloy with respect to the microstructures of the component has been investigated. The study has been carried out on a suspension arm injected in a rheocasting 800 tons plant in Stampal S.p.A. The new rheocasting is a process that allows obtaining the alloys in a semisolid state directly from the liquid state, by controlled cooling of the molten alloys. The resulting microstructures are very fine, free from defects and homogeneous: these characteristics improve the mechanical properties of the alloys and specially the response to cyclic stress, an important issue for a suspension component. After a preliminary tensile test analysis, axial high frequency fatigue tests have been carried out at room temperature on specimen cut out from the suspension arm to determine the Wöhler curve and the number of cycles to failure. The results of this work allow a comparison of the effects of heat treatment process, T5 or T6, on Semi-Solid components for industrial applications in the automotive field. On the basis of these analysis the correlation between microstructure and mechanical performances can be established.

Short-Term Oxidation Behavior, Microstructure Evolution and Compression Behavior of Nickel-Based Superalloy GH4037 in Solid and Semi-Solid States

2022 ◽  
Vol 327 ◽  
pp. 11-25
Author(s):  
Guan Fei Xiao ◽  
Ju Fu Jiang ◽  
Ying Wang ◽  
Ying Zhe Liu ◽  
Ying Zhang ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Deformation Mechanism ◽  
Deformation Zone ◽  
Solid Particles ◽  
Isothermal Treatment ◽  
Short Term ◽  
Solid States ◽  
Nickel Based Superalloy ◽  
Semi Solid ◽  
Solid Temperature

Semi-solid processing combines the advantages of traditional forging and casting methods, so it has received much attention recently. However, the research on semi-solid behaviors of Nickel-based superalloys has been rarely reported. In order to investigate the behaviors of Nickel-based superalloy at solid and semi-solid states, oxidation experiments, isothermal treatment experiments and deformation experiments of GH4037 alloy were studied. Short-term oxidation experiments of GH4037 alloy were carried out at a solid temperature (1200 °C) and a semi-solid temperature (1360 °C). The results indicated that the oxides formed at 1200 °C were mainly composed of TiO2, Cr2O3 and a small amount of spinels NiCr2O4, while the oxides formed at 1360 °C consisted of the spinels of NiCr2O4, NiWO4 and NiMoO4 besides TiO2 and Cr2O3. Microstructure evolution of GH4037 alloy after semi-solid isothermal treatment at 1370 °C and 1380 °C was studied. The results indicated that semi-solid microstructures consisted of equiaxed solid grains and liquid phases. The average grains size and shape factor of solid grains were affected by melting mechanism and grain growth mechanism. Compression behaviors of GH4037 alloy after compressed at 1200 °C and 1360 °C were investigated. The results indicated that the flow stress of 1360 °C decreased significantly compared to that of 1200 °C. The deformation zones in the specimens were divided into three parts: the difficult deformation zone, the large deformation zone, and the free deformation zone. At 1200 °C, the deformation mechanism was plastic deformation mechanism. At 1360 °C, sliding between solid particles (SS), liquid flow (LF), flow of liquid incorporating solid particles (FLS), plastic deformation of solid particles (PDS) coexisted in the compression specimen.

scholarly journals The study of Zn–Co alloy coatings electrochemically deposited by pulse current

2012 ◽  
Vol 66 (5) ◽  
pp. 749-757 ◽  
Author(s):  
Jelena Bajat ◽  
Miodrag Maksimovic ◽  
Milorad Tomic ◽  
Miomir Pavlovic
Keyword(s):  
Surface Roughness ◽  
Current Efficiency ◽  
Direct Current ◽  
Current Density ◽  
Pulse Current ◽  
Pulse Plating ◽  
Cathodic Current ◽  
Average Current Density ◽  
Corrosion Stability ◽  
Average Current

The electrochemical deposition by pulse current of Zn-Co alloy coatings on steel was examined, with the aim to find out whether pulse plating could produce alloys that could offer a better corrosion protection. The influence of on-time and the average current density on the cathodic current efficiency, coating morphology, surface roughness and corrosion stability in 3% NaCl was examined. At the same Ton/Toff ratio the current efficiency was insignificantly smaller for deposition at higher average current density. It was shown that, depending on the on-time, pulse plating could produce more homogenous alloy coatings with finer morphology, as compared to deposits obtained by direct current. The surface roughness was the greatest for Zn-Co alloy coatings deposited with direct current, as compared with alloy coatings deposited with pulse current, for both examined average current densities. It was also shown that Zn-Co alloy coatings deposited by pulse current could increase the corrosion stability of Zn-Co alloy coatings on steel. Namely, alloy coatings deposited with pulse current showed higher corrosion stability, as compared with alloy coatings deposited with direct current, for almost all examined cathodic times, Ton. Alloy coatings deposited at higher average current density showed greater corrosion stability as compared with coatings deposited by pulse current at smaller average current density. It was shown that deposits obtained with pulse current and cathodic time of 10 ms had the poorest corrosion stability, for both investigated average deposition current density. Among all investigated alloy coatings the highest corrosion stability was obtained for Zn-Co alloy coatings deposited with pulsed current at higher average current density (jav = 4 A dm-2).

scholarly journals Crystalline modification of a rare earth nucleating agent for isotactic polypropylene based on its self-assembly

2018 ◽  
Vol 5 (5) ◽  
pp. 180247 ◽  
Author(s):  
Yuanming Zhang ◽  
Tingting Sun ◽  
Wei Jiang ◽  
Guangting Han
Keyword(s):  
Hydrogen Bond ◽  
Rare Earth ◽  
Isotactic Polypropylene ◽  
Self Assembly ◽  
Dendritic Structure ◽  
Nucleating Agent ◽  
The Self ◽  
Structure Evolution ◽  
Crystalline Modification ◽  
Assembly Structure

In this paper, the crystalline modification of a rare earth nucleating agent (WBG) for isotactic polypropylene (PP) based on its supramolecular self-assembly was investigated by differential scanning calorimetry, wide-angle X-ray diffraction and polarized optical microscopy. In addition, the relationship between the self-assembly structure of the nucleating agent and the crystalline structure, as well as the possible reason for the self-assembly behaviour, was further studied. The structure evolution of WBG showed that the self-assembly structure changed from a needle-like structure to a dendritic structure with increase in the content of WBG. When the content of WBG exceeded a critical value (0.4 wt%), it self-assembled into a strip structure. This revealed that the structure evolution of WBG contributed to the K β and the crystallization morphology of PP with different content of WBG. In addition, further studies implied that the behaviour of self-assembly was a liquid–solid transformation of WBG, followed by a liquid–liquid phase separation of molten isotactic PP and WBG. The formation of the self-assembly structure was based on the free molecules by hydrogen bond dissociation while being heated, followed by aggregation into another structure by hydrogen bond association while being cooled. Furthermore, self-assembly behaviour depends largely on the interaction between WBG themselves.

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