Biaxial Tensile Deformation Behavior and Microstructural Evolutions of Superplasticity in AZ31 Magnesium Alloy

2007 ◽  
Vol 551-552 ◽  
pp. 225-230 ◽  
Author(s):  
M. Noda ◽  
Hideharu Shimizu ◽  
Kunio Funami ◽  
H. Mori
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Tensile Deformation ◽  
Grain Boundary Slide ◽  
Mg Alloys ◽  
Biaxial Stress ◽  
Recrystallization Temperature ◽  
Boundary Separation ◽  
Biaxial Tensile ◽  
Grain Structures

Magnesium alloys show promise in meeting the demand for materials of lighter weight and higher rigidity. Mg alloys are hard to process and normally require grain refining for improved formability and mechanical properties. To process these fine-grained Mg alloys effectively, it is important to relate their load stress and mechanical properties to changes in their microstructures. Using a biaxial tensile machine and cruciform specimens, to evaluate the mechanical properties, microstructure, and plasticity, in a high temperature biaxial stress state, used of AZ31 Mg alloy sheet. With biaxial deformation, grain boundary slide occurred more frequently than with uniaxial deformation, causing grain boundary separation and formation of micro-voids between the grains. In the vicinity of the cracks and at the locations of grain boundary separation, although deformation temperature at higher than the recrystallization temperature, fine grains (about 2 )m) showing in duplex grain structures were formed locally. The formation of duplex grain structures as a result of local formation of fine grains during the deformation process is a major issue to be solved from the viewpoint of plasticity processing.

Study on the Interface Characteristic of Superplastic Diffusion Bonding Joint of Dissimilar Steels

2007 ◽  
Vol 551-552 ◽  
pp. 157-162
Author(s):  
Min Wang ◽  
Hong Zhen Guo
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Grain Boundary Slide ◽  
Alloy Sheet ◽  
Mg Alloys ◽  
Biaxial Stress ◽  
Recrystallization Temperature ◽  
Local Formation ◽  
Boundary Separation ◽  
Grain Structures

Magnesium alloys show promise in meeting the demand for materials of lighter weight and higher rigidity. Mg alloys are hard to process and normally require grain refining for improved formability and mechanical properties. To process these fine-grained Mg alloys effectively, it is important to relate their load stress and mechanical properties to changes in their microstructures. Using a biaxial tensile machine and cruciform specimens, to evaluate the mechanical properties, microstructure, and plasticity, in a high temperature biaxial stress state, used of AZ31 Mg alloy sheet. With biaxial deformation, grain boundary slide occurred more frequently than with uniaxial deformation, causing grain boundary separation and formation of micro-voids between the grains. In the vicinity of the cracks and at the locations of grain boundary separation, although deformation temperature at higher than the recrystallization temperature, fine grains (about 2 μm) showing in duplex grain structures were formed locally. The formation of duplex grain structures as a result of local formation of fine grains during the deformation process is a major issue to be solved from the viewpoint of plasticity processing.

Deformation Behavior of Fine Grained Al-Mg Alloy under Biaxial Stress

2006 ◽  
Vol 503-504 ◽  
pp. 475-480 ◽  
Author(s):  
Masafumi Noda ◽  
Kunio Funami
Keyword(s):  
Grain Boundary ◽  
Tensile Deformation ◽  
Grain Boundary Sliding ◽  
Biaxial Stress ◽  
Mg Alloy ◽  
Strain Rates ◽  
Fine Grained ◽  
Biaxial Tensile ◽  
Wide Range ◽  
Boundary Sliding

The grain boundary sliding and the formation of slipped bands and cavitations during biaxial tensile deformation were examined in fine grained Al-Mg alloy. Biaxial tensile testing was conducted with cruciform specimens at initial strain rates of 10-4 to 101s-1. It was found that at the same equivalent strain conditions, the number of cavities under biaxial tension is significantly greater than that under uniaxial tension. A greater prevalence of slipped bands and grain separations were clearly observed under biaxial stress than under uniaxial stress. It was suggested that development of slipped bands resulted from the formation of elongated cavities and multiple deformed bands under biaxial stress. Additionally, the m-value under biaxial stress remained at about 0.3 over a wide range of strain rates. The effects of grain separation and formation of cavities were related to the motion of grain boundary sliding, grain size and loading conditions.

scholarly journals Effect of deformation and annealing temperature on the mechanical properties and microstructure of Al-4.5Zn-1.5Mg-0.9Cr (wt. %) alloy fabricated by squeeze casting

2018 ◽  
Vol 153 ◽  
pp. 01001
Author(s):  
Maya Putri Agustianingrum ◽  
Nuzulian Akbar Arandana ◽  
Risly Wijanarko ◽  
Bondan Tiara Sofyan
Keyword(s):  
Mechanical Properties ◽  
Squeeze Casting ◽  
Deformation Behaviour ◽  
Optical Microscope ◽  
Dislocation Motion ◽  
Hot Tearing ◽  
Mg Alloys ◽  
Recrystallization Temperature ◽  
Forming Process ◽  
Mechanical Properties And Corrosion

In order to produce structural products, Al-Zn-Mg alloys undergo various forming processes. Problems that are usually found in the forming process include peripheral coarse grain (PCG) and hot tearing which decrease mechanical properties and corrosion resistance of the alloys. Addition of microalloying element such as chromium (Cr) is an alternative to overcome these problems. The presence of Cr in Al-Zn-Mg alloys supresses the grain growth by preventing excess recrystallization. In this research 0.9 wt. % Cr was added to Al-4.5Zn-1.5Mg alloy and the deformation behaviour as well as subsequent recrystallization was observed. The alloy was fabricated by squeeze casting followed by homogenization at 400 °C for 4 h. The samples were cold rolled for 5, 10, and 20 %. The 20 % deformed samples were then annealed at 300, 400, and 500 °C for 2 h. Material characterization consisted of microstructure analysis using optical microscope and Scanning Electron Microscope (SEM) – Energy Dispersive Spectroscopy (EDS), hardness testing using Micro Vicker methods. The results showed that the deformed grain ratio was 1.6, 2.84, and 2.99 in the 5, 10, and 20 % deformed samples, respectively. The elongated dendrites were effective to increase the hardness of the alloy. Recrystallization was not detected during annealing at 300 and 400 °C, but was observed at 500 °C. Whereas, for the samples without Cr addition, recrystallization occurred at 400 °C. It means that the addition of Cr increased the recrystallization temperature of the alloy. It occured because (Al, Zn)7Cr dispersoids with size less than 1 μm impeded the dislocation motion during annealing, so that recrystallization was retarded. On the other hand (Al, Zn)7Cr dispersoids with size more than 1 μm promoted the formation of new grains around them by Particle Stimulated Nucleation (PSN) mechanism. In this case, the fine (Al, Zn)7Cr dominated so that recrystallization was slower.

Accommodation of Grain Boundary Sliding in AZ31 Alloy

2007 ◽  
Vol 345-346 ◽  
pp. 581-584
Author(s):  
Yong Nam Kwon ◽  
Young Seon Lee ◽  
S.W. Kim ◽  
Jung Hwan Lee
Keyword(s):  
Grain Boundary ◽  
Tensile Deformation ◽  
Texture Evolution ◽  
Grain Morphology ◽  
Superplastic Forming ◽  
Az31 Alloy ◽  
Grain Boundary Sliding ◽  
Processing Technique ◽  
Mg Alloys ◽  
Boundary Sliding

Mg alloys could be the lightest alloys among the industrially applicable engineering alloys. Since wrought Mg alloy has limited applications due to the poor formability, casting is currently the main processing technique to fabricate Mg components even though wrought alloys are superior in terms of mechanical properties and reliability. While a lot of research and development has been focused on warm forming under the temperature condition of around 250°C where more formability could be expected, superplastic forming could be another way to get over the low formability of Mg alloys. Like other superplastic materials grain boundary sliding is the main deformation mechanism of Mg superplasticity. Accommodation of stress concentration around triple point of grain boundary should be done favorably if grain boundary sliding continues without any fracture. In the present study, superplastic behavior of AZ31 alloys with several grain sizes was examined firstly. Accommodation of grain boundary sliding of AZ31 alloy would be discussed on the basis of grain morphology and texture evolution after tensile deformation.

scholarly journals Effect of the Zn/Mg Ratio on Microstructures, Mechanical Properties and Corrosion Performances of Al-Zn-Mg Alloys

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3299
Author(s):  
Keda Jiang ◽  
Yanquan Lan ◽  
Qinglin Pan ◽  
Yunlai Deng
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Grain Boundary ◽  
Stress Corrosion ◽  
Intergranular Corrosion ◽  
Optical Microscope ◽  
Mg Alloys ◽  
Sensitivity Index ◽  
Second Phase ◽  
Mechanical Properties And Corrosion

The effect of the Zn/Mg ratio on microstructures, mechanical properties and corrosion performances of Al-Zn-Mg alloys was studied. Microstructures were characterized using the optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). Tensile tests, intergranular corrosion (IGC) and stress corrosion cracking (SCC) tests were conducted to study the properties. Microstructures results indicated that with the decrease of the Zn/Mg ratio, the recrystallization proportion and the fraction of second phase decreased, while the size of η’ (MgZn2) phases in grain interior also significantly decreased. The number density of η’ phases in grain interior increased and grain boundary precipitates developed discontinuous distribution with the decrease of the Zn/Mg ratio. These microstructures contributed to the significant improvement of the strength and corrosion resistance. The tensile strength and yield strength increased by 34.1% and 47.4%, respectively, with the Zn/Mg ratio decreased from 11.4 to 6.1. Calculating results indicated that the enhancement of strength mainly contributed from the solid-solution strengthening, grain-boundary strengthening and precipitation strengthening. The intergranular corrosion degree was greatly relieved and the stress corrosion sensitivity index decreased from 0.031 to 0.007 with the Zn/Mg ratio decreased from 11.4 to 6.1.

Improvement of Strength and Ductility by Controlling PFZ with Microalloying Elements in Al-Zn-Mg Alloys

2007 ◽  
Vol 561-565 ◽  
pp. 235-238 ◽  
Author(s):  
Tomo Ogura ◽  
Shoichi Hirosawa ◽  
Tatsuo Sato
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Tensile Test ◽  
Tensile Properties ◽  
Aging Process ◽  
Mg Alloys ◽  
Proof Stress ◽  
Mode Change ◽  
Microalloying Elements ◽  
Strength And Ductility

The effectiveness of microalloying addition and two-step aging on the mechanical properties of the Al-Zn-Mg alloy has been investigated using TEM, tensile test and nanoindentation. By decreasing width of PFZ and size of grain boundary precipitates through the addition of (Ag+Sn) or two-step aging process, tensile properties of Al-Zn-Mg alloys are markedly improved. The elongation was quantitatively related to the three microstructural factors; i.e. the width of PFZ, size of grain boundary precipitates and the level of proof stress, to predict ductility of the alloys with known microstructural factors. The fracture mode change is reasonably in terms of the hardness difference between grain interiors and PFZ region by a noindentation technique.

Microstructure and Formability of Different-Speeds Rolled AZ31 Mg Sheet

2007 ◽  
Vol 544-545 ◽  
pp. 407-410 ◽  
Author(s):  
Jae Seol Lee ◽  
Hyeon Taek Son ◽  
Young Kyun Kim ◽  
Ik Hyun Oh ◽  
Chang Seog Kang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Yield Strength ◽  
Grain Boundary ◽  
Microstructure Evolution ◽  
Hot Rolling ◽  
Potential Application ◽  
Plastic Anisotropy ◽  
Mg Alloys ◽  
Az31 Mg Alloy

The aims of this study ares to investigate the microstructure evolution of AZ31 Mg alloys with normal rolling and different speeds rolling during hot rolling affects microstructure, texture and mechanical properties of AZ31 Mg alloy. In the microstructures of as-rolled both samples, twins are clearly apparent, small and recrystallized grains are visible along some grain boundary and twinned regions. The tensile strength and yield strength of DSR sample were slightly higher than that of NR sample. Also, in the case of the NR sample, tensile strength indicated different values to the rolling directions. From this result, NR sample compared to DSR sample strongly indicated to the plastic anisotropy tendency. Therefore, it is noted that DSR sample could be presented to the good formability, comparing to the NR sample. DSR samples deformed at 473K and 523K could be perfectly formed, indicating the potential application of the DSR process to improve formability of the Mg alloys at warm temperatures.

scholarly journals Mechanical Behavior and Microstructural Analysis of Molybdenum-TZM Alloy Subjected to Different Annealing Temperature

2020 ◽  
Vol 1 (1) ◽  
pp. 25-29
Author(s):  
Muhamad Anas Munawwar Ghazali ◽  
Mohd Azhar Harimon ◽  
Mohammad Sukri Mustapa
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Annealing Temperature ◽  
Microstructural Analysis ◽  
Hardness Test ◽  
Optical Microscope ◽  
Recrystallization Temperature ◽  
Micro Hardness ◽  
Annealing Heat Treatment ◽  
Vickers Micro Hardness

Mo-TZM alloy is one of the most famous economic molybdenum-based alloys. The percentage of chemical composition in mass of Mo-TZM alloy are Mo-0.5Ti-0.08Zr-0.03C. By adding some Titanium and Zirconium so that the mechanical properties and recrystallization temperature of molybdenum has been corresponding improvement. The purpose of this study is to determine the effect of different annealing temperature on mechanical properties of Mo-TZM alloy. The samples will be heated at two different temperature which are 1000 oC and 1300 oC in 1 hour and 40 minutes to change their microstructure behavior. The mechanical properties of the sample like hardness will be analyzed by using Vickers Micro hardness test. The force applied is 4.903 N and Vickers micro hardness number is 0.5 HVN for 10 second. Then to observe the microstructure changes, optical microscope and Scanning Electron Microscope (SEM) is be used. At annealing temperature 1000 oC, it show values of hardness is 249.54 VHN and the grain boundary size is 0.0898mm. While at annealing temperature 1300 oC, it show the lowest values of hardness which is 243.55 VHN and the highest grain boundary size which is 0.1068 mm. By doing annealing heat treatment it will decreases hardness values and increases the size of grain boundary

scholarly journals Grain Size Dependent Mechanical Properties in Nanophase Materials

1994 ◽  
Vol 362 ◽  
Author(s):  
Richard W. Siegel ◽  
Gretchen E. Fougere
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Grain Size ◽  
Grain Boundary ◽  
Present Knowledge ◽  
New Materials ◽  
Size Dependent ◽  
Grain Structures ◽  
Nanophase Materials ◽  
Property Changes

AbstractIt has become possible in recent years to synthesize metals and ceramics under well controlled conditions with constituent grain structures on a nanometer size scale (below 100 nm). These new materials have mechanical properties that are strongly grain-size dependent and often significantly different than those of their coarser grained counterparts. Nanophase metals tend to become stronger and ceramics are more easily deformed as grain size is reduced. The observed mechanical property changes appear to be related primarily to grain size limitations and the large percentage of atoms in grain boundary environments. A brief overview of our present knowledge about the grain-size dependent mechanical properties of nanophase materials is presented.

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