Fluidity and Microstructures Characteristics of AZ 91D by Using New Type Semi-Solid Injection Process

2006 ◽  
Vol 116-117 ◽  
pp. 534-537 ◽  
Author(s):  
Rudi S. Rachmat ◽  
Takuya Tamura ◽  
Kenji Miwa
Keyword(s):  
Temperature Distribution ◽  
Solid Particles ◽  
Permanent Mold ◽  
Uniform Temperature ◽  
Injection Speed ◽  
Injection Process ◽  
Fraction Solid ◽  
New Type ◽  
Semi Solid ◽  
Fluidity Test

This research has been investigated fluidity and microstructures characteristics of AZ 91 D alloy using new type semi-solid injection machine. To ensure good casting products, uniform temperature distribution was required during heating in the injection cylinder of this machine. So, the injection cylinder was divided with six heating zones. Then temperature distribution in the injection cylinder was precisely controlled. AZ 91 D billets were heated to the desired temperatures in the injection cylinder, and injected into the permanent mold with injection speed about 430 mm/s. Fluidity was measured by using spiral permanent mold with the cavity of 1045 mm in length and 5 mm in thickness. The fluidity test has been done with the fraction solid from 0% - 60%. The fluidity was 905 to 153 mm for fraction solid 0% to 60%, respectively. At the fraction solid from 50% to 60% microstructures are consisted of spherical solid particles and the solid particles surrounded by liquid phase. The shape of solid particles begins to change at the fraction solid of 40%.

Effect of Volume Fraction Solid and Injection Speed on Mechanical Properties in New Type Semi-Solid Injection Process

2008 ◽  
Vol 141-143 ◽  
pp. 761-766 ◽  
Author(s):  
Naoki Omura ◽  
Yuichiro Murakami ◽  
Ming Jun Li ◽  
Takuya Tamura ◽  
Kenji Miwa
Keyword(s):  
Mechanical Properties ◽  
Magnesium Alloy ◽  
Volume Fraction ◽  
Testing Machine ◽  
Permanent Mold ◽  
Injection Speed ◽  
Injection Process ◽  
Fraction Solid ◽  
New Type ◽  
Semi Solid

We have developed new type semi-solid injection process, that is, runner-less injection process which can obtain high material yield of about 90% for magnesium alloy. In this process, alloy billets are heated to the semi-solid temperature in the injection cylinder and are injected into a permanent mold. In order to investigate the effects of volume fraction solid and injection speed on microstructure and mechanical properties of AZ91D magnesium alloy injected into the permanent mold, semi-solid forming testing machine which has the same system as a runner-less injection machine, has been made on an experimental basis. The magnesium billet precisely controlled at given temperature has been injected into a permanent mold with two kinds (slow and high) of speed and plate-like specimens with each fraction solid have been fabricated. Microstructure has been observed by optical microscopy and X-ray computerized tomography (CT) scanner. Mechanical properties have been measured by tensile test. The effects of volume fraction solid of the alloy slurry and injection speed on mechanical properties have been clarified.

Effect of Solid Fraction on Microstructure and Casting Faults of AZ91D Alloys in New Type Semi-Solid Injection Process

2006 ◽  
Vol 116-117 ◽  
pp. 441-444 ◽  
Author(s):  
Kenji Miwa ◽  
Rudi S. Rachmat ◽  
Takuya Tamura
Keyword(s):  
Solid Fraction ◽  
Testing Machine ◽  
Solid Particles ◽  
Casting Defects ◽  
Permanent Mold ◽  
Forming Process ◽  
Injection Process ◽  
Controlling System ◽  
New Type ◽  
Semi Solid

We have developed new type semi-solid injection process, that is, runner-less injection process. In order to investigate the effects of solid fraction on microstructure and casting defects of AZ91D in new type semi solid injection process, semi-solid forming testing machine which has the same system as a runner-less injection machine has been made on an experimental basis. Its temperature controlling system has been established to obtain the homogeneous solid-liquid coexisted state in its injection cylinder. AZ91D billets are injected into a permanent mold by this machine in the semi-solid state. A shearing in the part of nozzle of injection cylinder is the most important to reveal thixotropic property of alloy slurry in semi solid forming process by injection machine. So it needs controlling of solid fraction to affect thixotropic property. In order to decrease casting defects and hold homogeneous structure, solid fraction more over 50% is needed. But when the solid fraction increases more than 50%, primary solid particles grow coarser, and then controlling method is required to suppress coarsening. In the case of less than 50% of solid fraction, liquid part preferentially fills inside the permanent mold and alloy slurry continue to fill the mold behind alloy liquid. Then large casting defects form at the boundary of both flows.

Development of New Type Semi-Solid Injection Process for Magnesium Alloy

2014 ◽  
Vol 217-218 ◽  
pp. 361-365
Author(s):  
Yuichiro Murakami ◽  
Kenji Miwa ◽  
Naoki Omura ◽  
Shuji Tada
Keyword(s):  
Magnesium Alloy ◽  
Volume Fraction ◽  
Solid Particles ◽  
Casting Defects ◽  
Microstructure Observation ◽  
Injection Process ◽  
Fraction Solid ◽  
The Matrix ◽  
New Type ◽  
Semi Solid

We have developed new type semi-solid injection process for magnesium alloy. This process does not require to use any cover gases and the special magnesium billet such as thixo-billet. In this study, plate specimens were produced by injecting the semi-solid billet with different fraction solid. The microstructure observation, detection of casting defects by an X-ray computed tomography scanner, and tensile test were carried out. With increasing fraction solid, the size and shape of α-Mg solid particles became smaller and more spherical. In the condition of low fraction solid or forming in liquid state, the casting defects were located in the center of the specimen at the thickness direction. Additionally, the volume fraction of the casting defect decreased with increasing fraction solid. Moreover, the casting defects can be reduced by preventing solidifying and clogging of the top of the nozzle. Then, the specimen which has few casting defects could be obtained by injecting the slurry of fraction solid 0.5. However, the tensile strength and yield strength were highest in fraction solid 0.4. It is contemplated that the composition of the solid solution component element in the matrix was increased in fraction solid of 50%, therefore the matrix became brittle.

Effect of Injection Speed on Microstructure of AZ91D Magnesium Alloy in Semi-Solid Injection Process

2012 ◽  
Vol 53 (6) ◽  
pp. 1094-1099 ◽  
Author(s):  
Yuichiro Murakami ◽  
Naoki Omura ◽  
Mingjun Li ◽  
Takuya Tamura ◽  
Kenji Miwa
Keyword(s):  
Magnesium Alloy ◽  
Injection Speed ◽  
Az91d Magnesium Alloy ◽  
Injection Process ◽  
Semi Solid

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.

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