scholarly journals A New Approach to Determine Tensile Stress-Strain Evolution in Semi-Solid State at Near-Solidus Temperature of Aluminum Alloys

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 396
Author(s):  
Jovid Rakhmonov ◽  
Mohamed Qassem ◽  
Daniel Larouche ◽  
Kun Liu ◽  
Mousa Javidani ◽  
...  
Keyword(s):  
Solid State ◽  
Aluminum Alloys ◽  
Accurate Determination ◽  
Solidus Temperature ◽  
Hot Tearing ◽  
Image Correlation ◽  
Correlation Technique ◽  
Stress Strain ◽  
Strain Evolution ◽  
Semi Solid

Accurate determination of the materials’ strength and ductility in the semi-solid state at near-solidus temperatures is essential, but it remains a challenging task. This study aimed to develop a new method to determine the stress-strain evolution in the semi-solid state of aluminum alloys within the Gleeble 3800 unit. Stress evolution was determined by the newly developed “L-gauge” method, which converted the displacement of the “restrained” jaw, measured using an L-gauge, into the force. This method gives the possibility to determine the flow stress more accurately, especially for the very low stress rang (1–10 MPa) in the semi-solid state at near-solidus temperatures. The digital image correlation technique implemented in the Gleeble unit allowed effective measurement of the heterogeneous strain fields evolving within the specimen under tensile loading. Therefore, the stress-strain curves measured in the semi-solid state help to better understand the alloy’s susceptibility to hot tearing. The results of an AA6111 alloy under different liquid fractions (2.8% at 535 °C and 5.8% at 571 °C) were demonstrated. The reliable stress-strain data and heterogenous strain distribution are beneficial to develop the thermomechanical models and hot-tearing criteria.

Inductive Reheating of Steel Billets into the Semi-Solid State Based on Pyrometer Measurements

2006 ◽  
Vol 116-117 ◽  
pp. 734-737 ◽  
Author(s):  
Alexander Schönbohm ◽  
Rainer Gasper ◽  
Dirk Abel
Keyword(s):  
Solid State ◽  
Measurement Errors ◽  
Liquid Fraction ◽  
Solidus Temperature ◽  
Measurement Data ◽  
Heating Process ◽  
Production Environment ◽  
Loop Control ◽  
Control Scheme ◽  
Semi Solid

The aim of the paper is to demonstrate a control scheme by which it is possible to reproducibly reheat steel billets into the semi-solid state. Usually a heating program is used to reheat the billet into the semi-solid state. Our experiments showed that this control scheme leads to varying semi-solid fractions from one experiment to the next. To gain information about the billet’s state its temperature is often used since there is a known relationship between the temperature and the liquid fraction. Direct measurement of the temperature via thermocouples is not feasible in a production environment, therefore a radiation pyrometer has been used as a contact-less measurement device. The accuracy of the pyrometer depends heavily on the exact knowledge of the radiation coefficient, which can vary from billet to billet due to different surface properties and which is subject to change during the heating process. These uncertainties prohibit the implementation of a closed-loop control scheme since the exact temperature cannot be measured with the required accuracy. In order to be independent of the measurement errors the proposed control scheme only relies on the slope of the temperature. By detecting the distinct change of slope which occurs when the solidus temperature is crossed, the beginning of the melting process can be determined. The energy fed to the billet from this point onward determines the resulting liquid fraction. By detecting the entry into the solidusliquidus interval and then feeding the same amount of energy to each billet, it is guaranteed that the billet reaches the desired liquid fraction even by uncertain absolute value of the temperature and by small variations of the alloy composition. For the experiments the steel alloy X210 has been used and measurement data demonstrate the feasibility of the proposed control scheme.

Reduction of Hot Tearing of Cast Semi-Solid 206 Alloys

2012 ◽  
Vol 192-193 ◽  
pp. 101-106 ◽  
Author(s):  
Alain Lemieux ◽  
Joseph Langlais ◽  
X. Grant Chen
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloys ◽  
Silicon Content ◽  
Hot Tearing ◽  
Silicon Concentration ◽  
Conventional Casting ◽  
Superior Mechanical Properties ◽  
High Silicon ◽  
Semi Solid

The mechanical properties of 206 alloys are among the highest of aluminum alloys. However, these alloys are usually prone to hot tearing. It is known that the addition of silicon can reduce the hot tearing propensity and improve fluidity. However, the commercial 206 alloys used in conventional casting processes limit the silicon concentration ≤0.05 wt% to obtain good mechanical properties. However, the semi-solid forming offers a unique opportunity to increase the silicon content to improve the castability without compromise on mechanical properties. In the present paper, the development of modified 206 alloy compositions to minimize hot tearing during semi-solid forming while maintaining competitive mechanical properties is reported. The effect of high silicon contents with varying copper levels on hot tearing sensitivity is studied. The mechanical properties of a high Si 206 alloy with lowest hot tearing sensitivity are evaluated. It is found that increasing the silicon content in 206 alloys is beneficial to reduce hot tearing. The high Si 206 variants produced by the SEED rheocating process not only reduce significantly the hot tearing sensitivity but also attain superior mechanical properties.

Mechanical Properties Improvement of Semi-Solid State Joining of Aluminum Alloys SSM A356

2015 ◽  
Vol 658 ◽  
pp. 146-150 ◽  
Author(s):  
Atsadawoot Geaowdee ◽  
Prapas Muangjunburee
Keyword(s):  
Mechanical Properties ◽  
Solid State ◽  
Aluminum Alloys ◽  
Welding Speed ◽  
Rotation Speed ◽  
Shielding Gas ◽  
Globular Structure ◽  
A356 Aluminum ◽  
Semi Solid ◽  
Solid State Joining

The aim of this research was to study semi-solid state joining of SSM A356 aluminum alloys which welded at its semi-solid state temperature by using oxygen – acetylene heat source. Then a stirrer was used to stir the weld seam. The joining parameters were rotation speed 1,110 with welding speed 120 mm/min and rotation speed 1,320 rpm with welding speed 160 mm/min. The joining temperatures were 575-590 and 590-610 oC. Joining was performed under nitrogen shielding gas and under argon shielding gas. Physical appearance, macrostructure, microstructure and mechanical properties were analyzed. The results indicated that the weld’s microstructure consisted of globular structure. In addition, porosities were found at the top of weld. However, minimum porosities were obtained from joints under argon shielding gas. The highest tensile strength was achieved from rotation speed at 1,110 rpm with welding speed at 120 mm/min under argon shielding gas with the value of 173 MPa. The joint efficiency was 86 % compared to the base metal.

Evaluation of Friction Stir Welds

2005 ◽  
Author(s):  
S. Adapa ◽  
T. P. Chu ◽  
J. A. Schneider
Keyword(s):  
Digital Image Correlation ◽  
Structural Properties ◽  
Material Properties ◽  
Image Correlation ◽  
Structural Behavior ◽  
Correlation Technique ◽  
Stress Strain ◽  
Friction Stir ◽  
Weld Material ◽  
And Behavior

An Image correlation technique to evaluate the structural properties and behavior of the Friction Stir Welds (FSW) is presented. The technique used is Sub-Pixel Digital Image Correlation (SPDIC). Four weld samples made of Al-2219 and Al-2195 alloys but different surface treatments are tested under tensile loads and the digital images of these samples are correlated using SPDIC. Stress-strain graphs and strain contours are obtained from the results. From the stress-strain graphs the structural properties and the behavior of the weld material are determined. The results indicate that SPDIC is a steadfast tool to determine the structural behavior and material properties of the weld samples.

Influence of Si and Mg Contents on the Mechanical Behavior of Al-Mg-Si Alloys in the Semi-Solid State under Isothermal and Non-Isothermal Conditions

2011 ◽  
Vol 690 ◽  
pp. 73-76
Author(s):  
Eliane Giraud ◽  
Michel Suéry ◽  
Michel Coret
Keyword(s):  
Solid State ◽  
Aluminum Alloys ◽  
Mechanical Behavior ◽  
Solid Fraction ◽  
Solid Alloy ◽  
Isothermal Conditions ◽  
Formation Of Cracks ◽  
Semi Solid ◽  
Si Content ◽  
Mg Content

The shear behavior of aluminum alloys containing increased amounts of Si or Mg compared with the 6061 alloy has been investigated by carrying out isothermal and non-isothermal tests in the mushy state during solidification. In isothermal conditions, it is shown that (i) an increase in Mg content leads to a more resistant semi-solid alloy compared with the 6061 alloy for the same solid fraction and (ii) an increase in Si content leads to a more brittle mushy alloy. In non-isothermal conditions, stress increases continuously with decreasing temperature with the formation of cracks for some compositions. This study shows that an increase in Mg content seems to be the most appropriate solution to reduce the formation of cracks in a solidifying 6061 alloy.

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