scholarly journals Effect of Reheating to the Semisolid State on the Microstructure of the A356 Aluminum Alloy Produced by Ultrasonic Melt-Treatment

2008 ◽  
Vol 141-143 ◽  
pp. 499-504 ◽  
Author(s):  
W. Khalifa ◽  
Yoshiki Tsunekawa ◽  
Masahiro Okumiya
Keyword(s):  
Growth Rate ◽  
Aluminum Alloy ◽  
Rate Constants ◽  
Ostwald Ripening ◽  
A356 Aluminum Alloy ◽  
Semisolid State ◽  
Melt Treatment ◽  
A356 Aluminum ◽  
Ultrasonic Melt Treatment ◽  
Semi Solid

The effect of reheating to the semisolid state (soaking treatment) on the microstructure evolution of the A356 aluminum alloy prepared by ultrasonic melt treatment was studied in this paper. The results showed that in general the longer the soaking process the larger and the more round the grains obtained. Higher roundness occurs at shorter soaking times in the fine-grained ascast samples, and at longer times in the inhomogeneous or the coarser-grained as-cast structures. The optimum thixotropic condition (high roundness, 0.72, and small globule sizes < 90 μm) are achieved after 5 min. soaking in the samples treated by UST at 623 and 620oC, which is the typical soaking time dictated by the industrial practice in SSM. The amount of entrapped eutectic as observed after soaking treatments is uniquely very small, suggesting that the UST-treated ingots will have better formability in the semisolid state. The growth rate constants are substantially low: in the order of 479-748 μm3/s. These growth rate constants are much lower than those reported for MHDcast A356 ingots. The growth rates of the samples produced by UST in the liquid state (i.e., 626, 623 and 620oC. Note that liquidus temperature is 619oC) are lower than those of the samples treated in the semi-solid temperatures, i.e., 617 and 614oC. The Ostwald ripening is most likely the dominant growth mechanism in the UST-treated samples during the soaking treatments. These results reveal the feasibility and competence of UST as a potential route for thixotropic feedstock production.

Influence of Morphology on the Rheological Behavior of Semi-Solid A356 Aluminum Alloy

2006 ◽  
pp. 601-605
Author(s):  
Heng Hua Zhang ◽  
Xian Nian Zhang ◽  
Guang Jie Shao ◽  
Luo Ping Xu ◽  
Yi Tao Yang ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Rheological Behavior ◽  
A356 Aluminum Alloy ◽  
A356 Aluminum ◽  
Semi Solid

The Research on the Annulus Electromagnetic Stirring for Preparing the Semisolid A356 Aluminum Alloy Slurry

2014 ◽  
Vol 217-218 ◽  
pp. 241-246
Author(s):  
Yue Long Bai ◽  
Jun Xu ◽  
Zhi Feng Zhang
Keyword(s):  
Aluminum Alloy ◽  
Electromagnetic Stirring ◽  
A356 Aluminum Alloy ◽  
Primary Particles ◽  
A356 Aluminum ◽  
Semi Solid ◽  
Gap Width

The effects of annulus gap width, stirring power and stirring frequency on the microstructure of the semi-solid A356 aluminum alloy slurry have been investigated by the annulus electromagnetic stirring (AEMS) technology The results show that narrow annulus gap , strong stirring power and high stirring frequency are advantageous to obtain the small spherical primarymicrostructure, the smaller the annulus gap width is, the bigger the stirring power is, and the higher the stirring frequency is, the more uniform, the smaller and the more spherical the microstructure is. So the high stirring frequency, narrow annulus gap, strong stirring power are beneficial to obtain the fine and spherical semisolid microstructure in AEMS. Also the results indicate that the primary particles are globular, small and distribute homogeneously in the AEMS.

Visualization of Micro-Segregations in A356 Aluminum Alloy by a Color Etching Method

2014 ◽  
Vol 794-796 ◽  
pp. 9-14
Author(s):  
Li Gao ◽  
Yohei Harada ◽  
Shinji Kumai
Keyword(s):  
Aluminum Alloy ◽  
Grain Growth ◽  
Solid Phase ◽  
Color Difference ◽  
Water Quenching ◽  
A356 Aluminum Alloy ◽  
Dendritic Microstructure ◽  
Spheroidal Microstructure ◽  
A356 Aluminum ◽  
Semi Solid

An A356 aluminum alloy billet which has a dendritic microstructure was compressed and then partially re-melted to semi-solid state before water quenching, by which the spheroidization of Al grains was realized. A color etchant called Weck's reagent was used to characterize both the dendritic and spheroidal microstructure. In both cases, distinct color differences were observed inside Al grains by normal optical microscopy. Interestingly, a dendritic-shaped structure inside the spheroidal Al grains was visualized, which should be the reflection of the original dendrite before heating and partial re-melting. Also, the grain growth during water quenching could be clearly visualized after etching with this reagent. As a result, solid fractions could be evaluated more precisely by excluding the grain growth when measuring the area of solid phase in 2-D micrographs. In order to investigate the coloring mechanism, electron probe micro-analyses were carried out to characterize the micro-segregations inside an Al grain. Results showed that the micro-segregation of Ti had a strong correlation with the color difference. Detailed investigation found that the micro-segregation of Ti could be preserved after heating and partial re-melting due to the extremely low diffusion rate of Ti in Al.

Study on Microstructures and Mechanical Properties of Rheo-Die Casting Semi-Solid A356 Aluminum Alloy

2006 ◽  
Vol 116-117 ◽  
pp. 453-456 ◽  
Author(s):  
Yong Lin Kang ◽  
Yue Xu ◽  
Zhao Hui Wang
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Die Casting ◽  
A356 Alloy ◽  
Experimental Results ◽  
A356 Aluminum Alloy ◽  
Microstructures And Mechanical Properties ◽  
A356 Aluminum ◽  
Semi Solid

In this paper, with a newly self-developed rotating barrel rheomoulding machine(RBRM), microstructures and mechanical properties of rheo-die casting A356 alloy were studied. In order to clearly show the characteristic of rheo-die casting, liquid die casting and semi-solid casting were done too. The experimental results showed that microstructures of rheo-die casting were composed of solid grains, which were finer and rounder, and had fewer pores. In the three technologies, integrated mechanical properties of semi-solid rheo-die casting were the best.

Influence of Morphology on the Rheological Behavior of Semi-Solid A356 Aluminum Alloy

2006 ◽  
Vol 116-117 ◽  
pp. 601-605
Author(s):  
Heng Hua Zhang ◽  
Xian Nian Zhang ◽  
Guang Jie Shao ◽  
Luo Ping Xu ◽  
Yi Tao Yang ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Solid State ◽  
Rheological Behavior ◽  
Apparent Viscosity ◽  
Flow Behavior ◽  
A356 Alloy ◽  
Solid Alloy ◽  
A356 Aluminum Alloy ◽  
A356 Aluminum ◽  
Semi Solid

The morphology of semi-solid alloy is one of the key influence factors on the rheological behavior of slurry during die filling and the mechanical properties of formed parts. However, it is difficult to study such effect due to hard controlling of morphology in semi-solid state. In this paper, a self-developed Searle-type viscometer was used to determine the rheological behavior of A356 aluminum alloy in different morphology, which was refined with the salts mixture of K2TiF6 and KBF4. The results indicated that the flow behavior of refined A356 alloy in the semi-solid state possesses obviously thixotropic behavior under isothermal shearing condition with less time to reach steady state and lower steady apparent viscosity as compared to that of the A356 alloy. During continuous cooling at a constant shearing rate, the apparent viscosity of refined A356 slurry in the same solid fraction decreased with the content of Ti. It is shown from quantitative image analysis that the primary α-Al grain in the refined alloy evolves from dendrites to rosettes or sphericitys, and then tends to be rounder and finer in higher Ti content. The mechanism of the influence of morphology on rheological behavior was also discussed in this paper.

Microstructure and Mechanical Properties of Semi-Solid Die-Cast A356 Aluminum Alloy

2016 ◽  
Vol 877 ◽  
pp. 39-44
Author(s):  
Si Min Lei ◽  
Li Gao ◽  
Yohei Harada ◽  
Shinji Kumai
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
A356 Aluminum Alloy ◽  
Microstructure And Mechanical Properties ◽  
Die Cast ◽  
Microstructural Evaluation ◽  
Cast Machine ◽  
A356 Aluminum ◽  
Semi Solid ◽  
The Relationship

The present work deals with the relationship between microstructure and mechanical properties of A356 aluminum alloy which was produced via thixocasting process under different casting conditions. Feedstock billets were heated to a target temperature to obtain a semi-solid slurry with the required solid fraction. Some billets were heated to a fully-melted condition. In order to obtain fine and spheroidized Al grains, some billets for the partially melting were compressed axially by 33% at a room temperature before heating. The completely-melted and partially-melted slurries were die-cast by using a die-cast machine, and hour glass-shaped rod-type tensile specimens and small-size plate-type tensile specimens were obtained. Small cubic specimens were also collected from the die-cast products for microstructural evaluation. They were polished, and etched by Weck’s reagent. The partially-melted specimen which was compressed before heating shows the spherical Al grains. But the grain of the strain-free partially-melted specimen exhibited complicated morphology. The fully-melted specimen shows the fine and dendrite structure.

scholarly journals Structure and mechanical properties of A356-C alloys

2018 ◽  
Vol 243 ◽  
pp. 00024
Author(s):  
Marina Khmeleva ◽  
Anton Khrustalev ◽  
Alexander Vorozhtsov
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Mechanical Characteristics ◽  
Casting Alloy ◽  
A356 Aluminum Alloy ◽  
Mechanical Mixing ◽  
Alloy Structure ◽  
Melt Treatment ◽  
Mechanical Tensile ◽  
A356 Aluminum

The paper deals with influence of mechanical mixing and vibration treatment on the structure and mechanical characteristics of the aluminum alloy containing ≤ 1 wt.% of nanodiamonds (A356-C). The alloy was obtained from industrial A356 Al-Si casting alloy by means of an integrated effect of mechanical mixing and vibration. It has been shown that the introduction of nanodiamond particles contributes to improving the alloy structure and increasing its mechanical tensile properties. The structure of the A356 aluminum alloy has been refined with introduction of 0.2 wt% nanodiamonds and application of vibration melt treatment. The introduction of nanodiamonds into the melt and the vibration melt treatment enable one to increase the yield strength and tensile strength of the A356 aluminum alloy without any change in ductility.

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