Thixotropic Behavior of Semi-Solid Magnesium Alloy

2006 ◽  
Vol 116-117 ◽  
pp. 648-651 ◽  
Author(s):  
Hsueh I Chen ◽  
Jyh Chen Chen
Keyword(s):  
Shear Stress ◽  
High Temperature ◽  
Magnesium Alloy ◽  
Shear Rate ◽  
Experiment Data ◽  
Az91d Magnesium Alloy ◽  
Thixotropic Behavior ◽  
Semi Solid ◽  
Rising Time ◽  
Shear Thinning Fluid

By a high-temperature Couette type viscometer, we studied the thixotropic behavior of the semi-solid AZ91D magnesium alloy slurry. According to different variable conditions, we could measure the change of the shear stress. The results showed that the shear stress of semi-solid AZ91D magnesium alloy slurry increased at starting shearing, and the shear stress fell down at the maintained shear rate shearing. In our experiment data, we found that the semi-solid AZ91D magnesium alloy slurry had the behavior of shear thinning fluid. As the maximum shear rate increased, the measured shear stress increased at a dissimilar level. When the rising time was shorter, the increasing range of shear stress was larger. As the shearing time of the maintained shear rate increased, the falling down degree of the shear stress increased and it can be presented as a function of shearing time, such as: e 0.0159t min 11331 τ = − . At the same shear rate, the area of hysteresis loop was bigger and the thixotropic behavior was more obvious.

Study on Static Shear-Rheologic Characteristics of Semi-Solid AZ91D Magnesium Alloy by Reheating

2006 ◽  
Vol 116-117 ◽  
pp. 738-741
Author(s):  
Ze Sheng Ji ◽  
Mao Liang Hu ◽  
Xiao Ping Zheng
Keyword(s):  
Shear Stress ◽  
Magnesium Alloy ◽  
Critical Shear Stress ◽  
Critical Value ◽  
Holding Time ◽  
Az91d Magnesium Alloy ◽  
Coarse Grains ◽  
Small Grains ◽  
Semi Solid ◽  
Static Shear

Static shear-rheology for self-made semi-solid AZ91D magnesium alloy slurry was studied by using the tester and a universal electronic machine. Shear-stress along with cylindrical surface in the sample was produced by using the tester and then shear-rheologic deformation happened. It showed that on the condition of the same loading, the longer the loading time and holding time were, the larger the deforming rate was. When the holding time attained a certain value, small grains acquired enough energy to grow up or amalgamate with prolonging the holding time and coarse grains started to melt from intergranular or grain boundaries, but the critical shear-stress kept a constant. The sample didn’t flow but appeared to instantaneous shear-strains with starting to load. When the loading exceeded the critical value, the sample started to flow and had the phenomena of elastic after-working, elastic before-working and remained deformation. The rheologic characteristics of semi-solid AZ91D magnesium alloy were expressed by the five element mechanical model: H1—(N1/H2)—(N2/S).

Thixotropic Strength and Thixotropic Criteria in Semi-Solid Processing

2008 ◽  
Vol 141-143 ◽  
pp. 319-323 ◽  
Author(s):  
W.C. Keung ◽  
Y.F. Lee ◽  
Wei Wei Shan ◽  
Shou Jing Luo
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Shape Factor ◽  
Shear Thickening ◽  
Solid Material ◽  
Solid Content ◽  
Solid Particles ◽  
Thixotropic Behavior ◽  
Semi Solid ◽  
Constant Shear Rate

Thixotropy is essential to semi-solid processing, and because of it the semi-solid material is characterized by ‘shear shinning’. Here, thixotropic strength and thixotropic criteria in semi-solid processing are put forward based on related theories and experiments, and thixotropic mechanism and its influencing factors are also investigated. The results are as follows: 1) the term of thixotropic strength means that with constant shear rate at semi-solid temperature, the semi-solid body begins to flow when the shear stress reach a certain value. This value of shear stress is defined as the thixotropic strength; 2) Thixotropic behavior happens with ‘shear thinning’ because of the deagglomeration of solid particles, while ‘shear thickening’ happens because of the agglomeration at the same time. With increasing shear time, the shear stress increases first and then decreases rapidly to reach a stable value. 3) There are three important factors that influence ‘thixotropic strength’: temperature (hence solid content), initial microstructure (including size, shape factor and uniformity of solid particles) and shear rate.

Microstructure Evaluate System of Semi-Solid Forming

2007 ◽  
Vol 546-549 ◽  
pp. 93-96 ◽  
Author(s):  
Xiao Peng Cui ◽  
Yong Bing Liu ◽  
Zhan Yi Cao ◽  
You Fa Zhang ◽  
Qian Qian Zhang
Keyword(s):  
Magnesium Alloy ◽  
The Other ◽  
Microstructure Analysis ◽  
Analysis Software ◽  
Az91d Magnesium Alloy ◽  
Alloy Microstructure ◽  
Semi Solid

The evaluating rules for semi-solid microstructure were brought up, and the analysis software was developed on MATLAB 7.0 platform in this study. Furthermore, this system can be used not only in the Thixomolding AZ91D magnesium alloy microstructure analysis, but also in the other semi-solid processing microstructure.

Study on Semi-Solid Continuous Roll-Casting Strips of AZ91D Magnesium Alloy

2008 ◽  
pp. 469-473
Author(s):  
Shui Sheng Xie ◽  
You Feng He ◽  
Guo Jie Huang ◽  
Mao Peng Geng ◽  
Ying Zhang
Keyword(s):  
Magnesium Alloy ◽  
Az91d Magnesium Alloy ◽  
Roll Casting ◽  
Semi Solid

scholarly journals Semi-solid forming of strain-induced AZ91D magnesium alloy.

1995 ◽  
Vol 45 (10) ◽  
pp. 560-565 ◽  
Author(s):  
Kazutoshi SEKIHARA ◽  
Satoshi OHNISHI ◽  
Shigeharu KAMADO ◽  
Yo KOJIMA
Keyword(s):  
Magnesium Alloy ◽  
Az91d Magnesium Alloy ◽  
Semi Solid

Simplified Rheocasting of Al-Si Alloys Sheared by Mechanical Stirring

2015 ◽  
Vol 651-653 ◽  
pp. 1545-1550 ◽  
Author(s):  
Alfredo Hernández ◽  
J. Federico Chávez ◽  
Raquel E. Hernández
Keyword(s):  
Stainless Steel ◽  
Solid State ◽  
Shear Rate ◽  
Microstructural Characterization ◽  
Dendritic Morphology ◽  
Solid Alloy ◽  
Mechanical Stirring ◽  
Simplified Method ◽  
Thixotropic Behavior ◽  
Semi Solid

A rheocasting prototype for the semi-solid processing of Al-Si alloys was designed and assembled at laboratory scale, this is the first attempt for the development of S2P equipment in Mexico. This work describes the simplified method of mechanical stirring and the calculation of the theoretical parameters for the operation of the experimental device in order to provide shear rate into the slurry by a stainless steel impeller inside a crucible made of hot work steel. Moreover, a vertical pressure die-rheocasting system it is applied with the semi-solid alloy flowing counter the position of the injector during the displacement of the crucible in order to fill the mold. New design is applied in this rheocasting equipment.The semi-solid state with thixotropic behavior is produced in the stirred AlSi7Mg alloy; this condition allows the non-dendritic morphology because the intensively stirring at the beginning of the solidification produces the trimming of dendrites, growing so the primary solid (α) in globular shape surrounded by eutectic microstructure. Preliminary microstructural characterization was performed.

Numerical Simulation of Thixoforging of an AZ91D Magnesium Alloy Magazine Plate and Experimental Validation

2008 ◽  
Vol 141-143 ◽  
pp. 623-628 ◽  
Author(s):  
Ju Fu Jiang ◽  
Ying Wang ◽  
Zhi Ming Du ◽  
Shou Jing Luo
Keyword(s):  
Numerical Simulation ◽  
Magnesium Alloy ◽  
Experimental Validation ◽  
Equivalent Strain ◽  
Technological Parameters ◽  
Billet Temperature ◽  
Az91d Magnesium Alloy ◽  
Punch Velocity ◽  
Die Temperature ◽  
Semi Solid

In this paper, thixoforging of a magazine plate made of AZ91D magnesium alloy were investigated by means of numerical simulation and experiments. Numerical simulation results show that with increasing punch displacement, local bending, formation of a concave shell part and bulk plastic deformation occurs in billet continuously. Equivalent strain and stress increase and the temperature of the semi-solid billet decreases. When the temperature of the semi-solid billet or the die temperature is elevated, equivalent stain and stress decrease. Optimal technological parameters such as a billet temperature of 545°C, die temperature of 450°C and punch velocity of 15 mm/s were obtained by numerical simulation. Experimental results demonstrate that magazine plates with high mechanical properties such as tensile strength of 316.8 MPa, yield strength of 228.3 MPa and elongation of 12.6 % can be manufactured successfully when the optimal technological parameters selected according to the results of numerical simulation are applied.

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