The Microstructure Evolution of a High Zr-Containing WE Magnesium Alloy Through Isothermal Semi-Solid Treatment

2015 ◽  
Vol 17 (11) ◽  
pp. 1623-1630 ◽  
Author(s):  
M. Moradjoy-Hamedani ◽  
A. Zarei-Hanzaki ◽  
S. M. Fatemi ◽  
Sh. Asqardoust
Keyword(s):  
Magnesium Alloy ◽  
Microstructure Evolution ◽  
Semi Solid

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.

scholarly journals Effect of Y Addition on the Semi-Solid Microstructure Evolution and the Coarsening Kinetics of SIMA AZ80 Magnesium Alloy

2017 ◽  
Author(s):  
Qi Tang ◽  
Hao Sun ◽  
Mingyang Zhou ◽  
Gaofeng Quan
Keyword(s):  
Magnesium Alloy ◽  
Microstructure Evolution ◽  
Shape Factor ◽  
Ostwald Ripening ◽  
Optical Microscope ◽  
Isothermal Treatment ◽  
Az80 Magnesium Alloy ◽  
Coarsening Kinetics ◽  
Semi Solid ◽  
Az80 Alloy

Semi-solid feedstock of AZ80 magnesium alloy modified by minor rare-earth Y element (0, 0.2, 0.4, 0.8 wt.%) were fabricated by strain induces melting activated (SIMA) in the form of extrusion and partial remelting. The effect of Y addition on the microstructure evolution of extruded and isothermal treated alloy was observed by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD) and quantitative analysis. The results show that the Y addition can refine the microstructure and make the β-Mg17Al12 phases agglomerating. During the subsequent isothermal treatment at 570℃, the average solid grain size, shape factor and liquid fractions increased with prolonged soaking time. Smaller spheroidal solid grains and the larger shape factor were obtained due to Y addition. The coalescence and Ostwald ripening of solid grains operated the coarsening process simultaneously. The coarsening rate constants of AZ80M1 (0.2 wt.% Y addition) of 164.22 μm3s-1 was approximately four times less than the un-modified AZ80 alloy of 689.44 μm3s-1. In contrast, the desirable semi-solid structure featured by fine, well globular solid grains and appropriate liquid fractions and shape factor was achieved in AZ80M1 alloy treated at 570℃ for 20-30 min.

The Influence of Electric Current Pulses on the Microstructure of Magnesium Alloy AZ91D

2005 ◽  
Vol 488-489 ◽  
pp. 201-204 ◽  
Author(s):  
Yuan Sheng Yang ◽  
Quan Zhou ◽  
Zhuang Qi Hu
Keyword(s):  
Magnesium Alloy ◽  
Electric Current ◽  
Microstructure Evolution ◽  
Nucleation Rate ◽  
Low Voltage ◽  
Az91d Alloy ◽  
Current Pulses ◽  
Alloy Az91d ◽  
Electric Current Pulses ◽  
Semi Solid

The microstructure evolution of magnesium alloy AZ91D solidified with different electric current pulses and cooling rates was investigated and a new method, Low-voltage Electric Current Pulses (LVECP), to produce semi-slurry magnesium alloy was developed in this paper. The experimental results showed that the electric current pulses during solidification changed morphology of dendrites and the equiaxed, non-dendritic grains formed. The size of the primary a-Mg particles in semi-solid AZ91D alloy and the sphericity of the particles decreased with increase of discharging the voltage and treating time of LVECP. The increase of the cooling rate during the solidification of AZ91D alloy with LVECP promoted the formation of finer a-Mg particles, but the value of the sphericity of the particles rised. The formation of equiaxed, nondendritic structure by LVECP might be attributed to the electric current pulses increase the nucleation rate, restrained growth of the dendrites, and made dendrite arms remelted during the solidification of AZ91D alloy.

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