Effect of Disturbing Conditions in Semi-Solid State on Microstructure Evolution of Magnesium Alloy

2006 ◽  
Vol 116-117 ◽  
pp. 296-299 ◽  
Author(s):  
Hong Jin Zhao ◽  
Yong Lin Kang ◽  
Zhao Hui Wang ◽  
Hai Liang Du
Keyword(s):  
Solid State ◽  
Magnesium Alloy ◽  
Microstructure Evolution ◽  
High Efficiency ◽  
External Disturbance ◽  
Dendritic Structure ◽  
Good Effect ◽  
Mechanical Stirring ◽  
Β Phase ◽  
Semi Solid

In this paper the microstructure evolution of AZ91HP magnesium alloy casts produced under different disturbing treatment conditions such as non-disturbing, argon blowing and mechanical stirring in semi-solid state after holding a short time was studied. The results show that the grains of AZ91HP alloy casts refined, the secondary dendritic arms grown and the dendrites tend to rosette shape with the decrease of holding temperature. External disturbance can accelerate the evolution process, and the spherical primary α phase formed easily under mechanical stirring treatment condition. The formation of non-dendritic structure is owing to ripening of the dendritic arms, refinement of the grains and movement of the primary formed solid phases. Disturbing treatments in semi-solid state induce more equilibrium solidification and decrease the amount of brittle β-Mg17Al12 phase. Blowing argon into the refined and modified magnesium alloy in semi-solid state can obtain homogeneous non-dendritic structure and the net shaped β phase distributed on α-Mg phase boundaries become fine and thin, this may be have a good effect on the mechanical properties of the magnesium alloy casts. Due to the low disturbing strength, argon blowing can maintain the metallurgy quality of the semi-solid slurry well, and also have high efficiency to make it. This technology need not new complex equipments and can be practiced in conventional casting conditions, so it may be used in industrialize manufacture.

Microstructure Evolution of Deformed Magnesium Alloy in Semi-Solid State

2005 ◽  
Vol 488-489 ◽  
pp. 313-316
Author(s):  
Sen Yuan ◽  
Wu Xiao Wang ◽  
Bai Ling Jiang
Keyword(s):  
Solid State ◽  
Magnesium Alloy ◽  
Microstructure Evolution ◽  
High Energy ◽  
Mg Alloy ◽  
Continuous Heating ◽  
Heating Process ◽  
Semisolid State ◽  
Semi Solid ◽  
Temperature Time

Magnesium alloy slurry was prepared using Strain-Induced Melt Activation(SIMA) technique. The samples were quenched into water so as to fix the high temperature instantaneous microstructures. The microstructure evolution of compressed deformation Mg alloy is studied in the process of continuous heating and iso-temperature of semi-solid state. The results indicate that deformed Mg alloy (AZ91) has first occurred to have the conversion of dendrite crystal-oriented isometric crystals in the continuous heating process. When the temperature rises to the range of semisolid state, the region with high energy at the pressed stripes begins to melt, showing that the cellular structures emerge in the crystal boundary and melting micro-pool phenomena appear within the crystals. With the iso-temperature time in semisolid state prolongs, the isometric crystals can be gradually converted into spherical crystal grains.

Study on Semi-Solid Magnesium Alloy Produced by Mechanical Stirring

2010 ◽  
Vol 146-147 ◽  
pp. 1723-1728
Author(s):  
Bing Feng Zhou ◽  
Hong Yan
Keyword(s):  
Magnesium Alloy ◽  
Cooling Rate ◽  
Dendritic Structure ◽  
Spherical Particles ◽  
Solid Alloy ◽  
Mechanical Stirring ◽  
Stirring Rate ◽  
Stirring Time ◽  
Semi Solid ◽  
Spherical Grains

Semi-solid magnesium alloy slurry was produced by a newly self-developed mechanical stirring machine in order to prepare continuous semi-solid slurry. The changing principle of semi-solid microstructure was studied under different conditions—the changing of temperature, stirring rate, cooling rate and stirring time. It was showed that the lower the temperature of slurry, the higher the stirring rate, the longer the stirring time and the faster the cooling rate, the grain will be smaller and more evenly rounded. When the stirring speed and temperature are the same, better semi-solid spherical grains can be gained by increasing the stirring time. At the same stirring temperature and higher stirring speed, semi-solid spherical particles are smaller, rounder and more evenly; at a low stirring speed, we can't get ideal semi-solid spherical grains even if we increase the stirring time. The ideal technological parameters of semi-solid AZ61 alloy produced with no-dendritic structure were recommended to be 600°C～605°C (stirring end temperature) 、3min～ 5min(stirring time) and 500r/min(stirring rate). Compared with conventional casting alloy, semi-solid alloy mechanical properties were greatly improved. The non-dendrite semi-solid forming mechanism was studied; mechanical stirring semi-solid non-dendritic formation was the result of a variety of factors, the key cause is mechanical shear stress.

Microstructural evolution of an ECAE-formed ZK60-RE magnesium alloy in the semi-solid state

2009 ◽  
Vol 506 (1-2) ◽  
pp. 8-15 ◽  
Author(s):  
Zude Zhao ◽  
Qiang Chen ◽  
Yanbin Wang ◽  
Dayu Shu
Keyword(s):  
Solid State ◽  
Magnesium Alloy ◽  
Microstructural Evolution ◽  
Semi Solid

Microstructure and Mechanical Properties of Sn-Bi Alloy Treated in the Semi-Solid State by Mechanical Stirring Process

2010 ◽  
Vol 150-151 ◽  
pp. 1768-1771 ◽  
Author(s):  
Feng Li ◽  
Yong Jun Hu ◽  
Xiao Ling Cheng ◽  
Xiao Ting Xiao
Keyword(s):  
Mechanical Properties ◽  
Solid State ◽  
Die Casting ◽  
Percentage Elongation ◽  
Mechanical Stirring ◽  
Microstructure And Mechanical Properties ◽  
Stirring Time ◽  
Microstructures And Mechanical Properties ◽  
Semi Solid

In this work, the effect of stirring time on the solidifed microstructures and mechanical properties of semi-solid Sn-Bi slurry was investigated by the mechanical stirring method. The results indicated that a fine round granular solidifed structure of Sn-Bi semi-solid slurry was obtained at 142 and stirred for 8 min. Compared with the Sn-Bi alloy prepared conventional die casting, the mechamical properties of semi-solid Sn-Bi alloy was improved prominently. The percentage elongation of semi-solid Sn-Bi alloy was increased 67 % compared with that of the Sn-Bi alloy prepared conventional die casting.

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.

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