Superplastic Deformation of Twin Roll Cast AZ31 Magnesium Alloy

2008 ◽  
Vol 604-605 ◽  
pp. 267-277 ◽  
Author(s):  
Lorella Ceschini ◽  
Mohamad El Mehtedi ◽  
Alessandro Morri ◽  
Giuliano Sambogna ◽  
S. Spigarelli
Keyword(s):  
Magnesium Alloy ◽  
Superplastic Deformation ◽  
Large Fraction ◽  
Tensile Tests ◽  
Testing Temperature ◽  
Grain Boundary Sliding ◽  
Az31 Magnesium Alloy ◽  
Molten Metals ◽  
Superplastic Behaviour ◽  
Twin Roll

The aim of the present work was to evaluate the potential for superplastic deformation of the AZ31 magnesium alloy produced by Twin Roll Casting (TRC), a continuous casting technology able to convert molten metals directly into a coiled strip. In order to develop a superplastic microstructure, the TRC sheets were heated at 400 °C for 2 h, then rolled by multiple passes with re-heating between them, with a total thickness reduction of about 60%. The superplastic behaviour of the alloy was studied by tensile tests, carried out at in the temperature range from 400 °C to 500 °C and with initial strain rates of 1•10-3 s-1 and 5•10-4 s-1. The microstructural and fractographic characterization of the alloy was carried out by means of optical (OM) and scanning electron microscopy (SEM). The tensile tests evidenced a superplastic behaviour of the processed AZ31 Mg alloy, with a maximum elongation to failure of about 500% at 460 °C, with a strain rate of 5•10-4 s-1. The microstructure of the alloy after superplastic deformation showed fine and equiaxed grains, with a large fraction of high angle boundaries. Analyses of the fracture surfaces evidenced flow localization around the grains, suggesting that grain boundary sliding (GBS) was the main deformation mechanism. Failure occurred by cavitation, mainly at the higher testing temperature, due to the prevailing effect of grain growth.

STUDY ON HIGH STRAIN RATE COMPRESSION SUPERPLASTICITY OF AS-EXTRUDED AZ31 MAGNESIUM ALLOY

2013 ◽  
Vol 27 (19) ◽  
pp. 1341022 ◽  
Author(s):  
FEI LIN ◽  
JIE LI ◽  
HONGWEI ZHAO ◽  
LULU SUN ◽  
ZHITONG CHEN ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
High Strain Rate ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
High Strain ◽  
Orthogonal Experiment ◽  
True Strain ◽  
Grain Boundary Sliding ◽  
Az31 Magnesium Alloy ◽  
Boundary Sliding

The grain size of as-extruded AZ31 magnesium alloy was refined by isothermal annealing pretreatment through orthogonal experiment. By using the Gleeble-3800 thermal simulator, the compression superplasticity of as-extruded AZ31 magnesium alloy was studied. The high strain rate superplastic compression was realized. The process parameters of the superplastic compression were established and the mechanism of the superplastic deformation was analyzed. The effects of deformation temperature and strain rate on the superplastic flow were investigated. The results indicated that at 250°C–300°C and strain rate at 1×10-2 s -1, the true strain values were all more than 2.03. As the temperature was 300°C and the strain rate was 1×10-2 s -1–1×10 s -1, the true strain values were all more than 2.18. The results showed that the as-extruded AZ31 magnesium alloy being refined presented good compression superplasticity. The main mechanism for the superplastic compressive deformation of the as-extruded AZ31 magnesium alloy was grain-boundary sliding, meanwhile, dynamic recrystallization also played a harmonious role during the superplastic deformation.

Enhanced Grain-Boundary Sliding at Room Temperature in AZ31 Magnesium Alloy

2003 ◽  
Vol 419-422 ◽  
pp. 237-242 ◽  
Author(s):  
R. Ohyama ◽  
Junichi Koike ◽  
T. Kobayashi ◽  
Mayumi Suzuki ◽  
Kouichi Maruyama
Keyword(s):  
Magnesium Alloy ◽  
Grain Boundary ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Az31 Magnesium Alloy ◽  
Boundary Sliding

SUPERPLASTIC FORMABILITY OF AZ31 MAGNESIUM ALLOY SHEETS PRODUCED BY TWIN ROLL CASTING AND SEQUENTIAL HOT ROLLING

2013 ◽  
Vol 27 (19) ◽  
pp. 1341020
Author(s):  
YANDONG YU ◽  
KAI LIN ◽  
PENG JIANG
Keyword(s):  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Hot Rolling ◽  
Tensile Testing ◽  
Az31 Magnesium Alloy ◽  
Twin Roll Casting ◽  
Roll Casting ◽  
Three Stages ◽  
The Common ◽  
Twin Roll

In this paper, superplastic tensile testing and gas bulging forming of AZ31 and AZ31 + Y + Sr magnesium alloys produced by twin roll casting (TRC) and sequential hot rolling were carried out. At 673 K, the superplastic formability of the TRC AZ31 magnesium alloy sheets added Y and Sr elements has improved significantly compared to the common TRC AZ31 sheets. Formations of cavities on the bulging part go through three stages of the nucleation, growth and aggregation, finally cavities merging lead to rupture at the top of the bulging part.

Evaluation of Plastic Workability Limit of Magnesium Alloy by Cavitations in High Temperature Uni and Biaxial Test

2012 ◽  
Vol 735 ◽  
pp. 67-72
Author(s):  
Kunio Funami ◽  
Daisuke Yamashita ◽  
Kohji Suzuki ◽  
Masafumi Noda
Keyword(s):  
Fine Structure ◽  
High Temperature ◽  
Magnesium Alloy ◽  
Grain Boundary ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Az31 Magnesium Alloy ◽  
Temperature Deformation ◽  
Alloy Plate ◽  
Boundary Sliding

Abstract. This study examined the critical plastic formability limit of a fine-structure AZ31 magnesium alloy plate under warm and high temperature based on the strength of a magnesium alloy that has cavities at room temperature. The cyclic hot free-forging process as pre-form working following rolling at a light reduction ratio fabricated a fine-structure AZ31 magnesium alloy plate. The appearance of the cavities was examined in detail together with changes in the structure and preparation methods before further damage at high temperatures with increasing uni-and biaxial plastic deformation. The allowable deformation limit in the super plasticity process can be estimated from the strength of the deformed material and forming limit diagram (FLD) at room temperature. During high-temperature deformation, cavities are produced by stress concentrations at grain boundary triple points and striation bands due to grain boundary sliding. The cavitations growth behavior is dependent upon deformation conditions, and a high percentage of large cavities occupy the sample surface as a large amount of grain boundary sliding is present, i.e., as uniform elongation grows larger, the cavity size also increases. In a case where 200% uniaxial strain was applied to a fine-grained structure material at a temperature of 623K under a strain rate of 10-4s-1, the tensile strength at room temperature decreased about 13%, and elongation was 10% less, compared with that of a material to which no load was applied due to the influence of cavities. In a case of biaxial deformation, the values were 28% lower. It is possible to draw a FLD based on the cavity incidence fraction .

scholarly journals Determination of the Hot Cracking Tendency of a Twin-Roll Cast AZ31 Magnesium Alloy by Means of Gleeble Tests

2018 ◽  
Vol 918 ◽  
pp. 40-47
Author(s):  
Heike Wemme ◽  
Christina Krbetschek ◽  
Madlen Ullmann ◽  
Anna Freigang ◽  
Stefan Plach ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Az31 Alloy ◽  
Hot Cracking ◽  
Az31 Magnesium Alloy ◽  
Cast Magnesium ◽  
Twin Roll Cast ◽  
Twin Roll ◽  
Cracking Tendency

The knowledge about the formation of hot cracking in magnesium alloys, such as in twin-roll cast magnesium sheets and strips, is fundamental for a good quality of the strips during the further processing by rolling or welding and minimize the reject. Hot cracking often occurs in the so-called mushy zone, when solid phases and melt coexist, at temperatures where the material no longer exhibits ductility. For the evaluation of the hot cracking tendency of an alloy, the width of the HTBR (High-temperature brittleness range) can be used. On the basis of a test on a Gleeble HDS-V40, the HTBR was determined for a twin-roll cast AZ31 magnesium alloy. The transition between ductile forming behaviour and complete brittle reaction of the AZ31 alloy is confirmed by the observation of the fracture surfaces (determination of the fracture type) in the scanning electron microscope (SEM) and is located at 555 °C. The HTBR shows a range 35 K.

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