Sheet Orientation Effects on the Hot Formability Limits of Lightweight Alloys

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Fadi Abu-Farha ◽  
Louis G. Hector
Keyword(s):  
Rolling Direction ◽  
Superplastic Forming ◽  
Strain Ratio ◽  
Forming Limit ◽  
Specific Strain ◽  
Plastic Forming ◽  
Lightweight Alloys ◽  
Quick Plastic Forming ◽  
The Relationship ◽  
5083 Aluminum Alloy

The formability curves of AZ31B magnesium and 5083 aluminum alloy sheets were constructed using the pneumatic stretching test at two different sets of forming conditions. The test best resembles the conditions encountered in actual hydro/pneumatic forming operations, such as the superplastic forming (SPF) and quick plastic forming (QPF) techniques. Sheet samples were deformed at (400 °C and 1 × 10−3 s−1) and (450 °C and 5 × 10−3 s−1), by free pneumatic bulging into a set of progressive elliptical die inserts. The material in each of the formed domes was forced to undergo biaxial stretching at a specific strain ratio, which is simply controlled by the geometry (aspect ratio) of the selected die insert. Material deformation was quantified using circle grid analysis (CGA), and the recorded planar strains were used to construct the forming limit curves of the two alloys. The aforementioned was carried out with the sheet oriented either along or across the direction of major strains in order to establish the relationship between the material’s rolling direction and the corresponding limiting strains. Great disparities in limiting strains were found in the two orientations for both alloys; hence, a “composite FLD” is introduced as an improved means for characterizing material formability limits.

Forming Limit Diagrams for AA5083 under SPF and QPF Conditions

2007 ◽  
Vol 551-552 ◽  
pp. 129-134 ◽  
Author(s):  
Mary Anne Kulas ◽  
Paul E. Krajewski ◽  
John R. Bradley ◽  
Eric M. Taleff
Keyword(s):  
Strain Rate ◽  
Plane Strain ◽  
Superplastic Forming ◽  
Forming Limit ◽  
Forming Limit Diagrams ◽  
Commercial Grade ◽  
Bulge Testing ◽  
Macroscopic Fracture ◽  
Plastic Forming ◽  
Quick Plastic Forming

Forming Limit Diagrams (FLD’s) for AA5083 aluminum sheet were established under both Superplastic Forming (SPF) and Quick Plastic Forming (QPF) conditions. SPF conditions consisted of a strain rate of 0.0001/s at 500°C, while QPF conditions consisted of a strain rate of 0.01/s at 450°C. The forming limit diagrams were generated using uniaxial tension, biaxial bulge, and plane strain bulge testing. Forming limits were defined using two criteria: (1) macroscopic fracture and (2) greater than 2% cavitation. Very little difference was observed between the plane strain limits in the SPF and QPF conditions indicating comparable formability between the two processes with a commercial grade AA5083 material.

Sheet Orientation Effects on the Formability Limits of the AZ31B Magnesium Alloy at SPF Conditions

2011 ◽  
Author(s):  
Fadi Abu-Farha ◽  
Brad Deeter
Keyword(s):  
Magnesium Alloy ◽  
Rolling Direction ◽  
Constant Strain Rate ◽  
Forming Limit Diagram ◽  
Superplastic Forming ◽  
Strain Ratio ◽  
Forming Limit ◽  
Az31b Magnesium Alloy ◽  
Novel Approach ◽  
Mechanical Stretching

The formability curves of the AZ31B magnesium alloy were constructed by following a novel approach that best resembles the conditions of actual Superplastic Forming (SPF) operations. Sheet samples were formed at 400 °C and a constant strain rate of 1×10−3 s−1, by free pneumatic bulging into a set of progressive elliptical die inserts. By doing so, the material in each of the formed domes was forced to undergo biaxial stretching at a distinct strain ratio, which is simply controlled by the geometry (aspect ratio) of the selected die insert. Material deformation was quantified using circle grid analysis (CGA), and the recorded planar strains were used to construct the forming limit diagram (FLD) of the material. The aforementioned was carried out with the sheet oriented either along or across the direction of major strains, in order to establish the relationship between the material’s rolling direction and the corresponding limiting strains. Great deviations between the two sets of formability curves are realised, hence a compound forming limit diagram is constructed as an improved way for characterising the material behaviour. The presented pneumatic stretching approach is shown to produce accurate friction-independent formability diagrams, with clear distinction between the safe and unsafe deformation zones, even though the developed diagrams are confined to the biaxial strain region (right side quadrant of an FLD). Moreover, the approach proves to be a viable means for providing formability maps under conditions where traditional mechanical stretching techniques (Nakajima and Marciniak tests) are limited.

Tribological Testing of Graphite and Boron Nitride Lubricant Formulations for High Temperature Aluminum Sheet Forming Processes

2007 ◽  
Author(s):  
M. David Hanna ◽  
Paul E. Krajewsk ◽  
James G. Schroth
Keyword(s):  
High Temperature ◽  
Boron Nitride ◽  
Superplastic Forming ◽  
Solid Lubricants ◽  
Sheet Forming ◽  
Aluminum Sheet ◽  
Plastic Forming ◽  
Quick Plastic Forming ◽  
Performance And Evaluation

The tribological behavior of AA5083 aluminum sheet sliding against tool steel impacts the quality of components manufactured with the elevated temperature metal forming processes such as Quick Plastic Forming (QPF), Superplastic Forming (SPF), or warm forming. This study focuses on the tribological performance and evaluation of alternative solid lubricants using a flat-on-flat tribo-tester to simulate sheet forming at high temperature applications. Improved lubricant formulations containing boron nitride with graphite additions were found to enhance lubricity while maintaining good adherence to the surface of the aluminum blank at a temperature of 450°C.

Forming Limit Diagram of Magnesium Alloy ZK60 at Elevated Temperature

2011 ◽  
Vol 308-310 ◽  
pp. 2442-2445 ◽  
Author(s):  
Hong Wei Liu ◽  
Sheng Jie Yao ◽  
Wen Liang Liu ◽  
Zhao Duo Zhang
Keyword(s):  
Elevated Temperature ◽  
Magnesium Alloy ◽  
Grain Boundaries ◽  
Forming Limit Diagram ◽  
Strain Ratio ◽  
Instability Criterion ◽  
Forming Limit ◽  
Relationship Of ◽  
Zk60 Magnesium Alloy ◽  
The Relationship

The forming limit diagram of magnesium alloy ZK60 was developed with Hill’s instability criterion and M-K analysis. The relationship of forming limit with stain path, temperature and the thickness irregular coefficient were analyzed. The results show that the forming limit of ZK60 magnesium alloy increased little with the rising of strain ratio, but influenced greatly by the failure definition , and forming limit of is increased with the rising of temperature and thickness irregular coefficient, the most suitable value of f0 is 0.99, the fracture occur on the grain boundaries with significant cavities formation.

Hot Tensile Behavior of Superplastic and Commercial AA5083 Sheets at High Temperature and Strain Rate

2013 ◽  
Vol 554-557 ◽  
pp. 63-70 ◽  
Author(s):  
Stefania Bruschi ◽  
Andrea Ghiotti ◽  
Francesco Michieletto
Keyword(s):  
High Temperature ◽  
Strain Rate ◽  
Automotive Industry ◽  
Hot Stamping ◽  
Superplastic Forming ◽  
Tensile Behavior ◽  
Tensile Behaviour ◽  
Fine Grained ◽  
Plastic Forming ◽  
Quick Plastic Forming

Since the last two decades, the automotive industry has dedicated an increasing attention to the manufacturing of sheet components made of high-resistant aluminium alloys; the superplastic AA5083 grade is currently utilized in both the conventional superplastic forming and the recently patented quick plastic forming, which assures higher productivity compared to that of superplastic forming, while the commercial AA5083 grade is rarely employed. The objective of the paper is to compare the hot tensile behaviour of commercial and fine-grained AA5083 sheets when processed at high temperature and strain rate, which are typical of hot stamping processes. The results are presented and commented in terms of flow stress, anisotropy, strain at failure, microstructural and hardness features as a function of temperature and strain rate. On the basis of the obtained results, the set of optimal forming conditions for the two grades is identified.

scholarly journals Coupled Thermomechanical Response Measurement of Deformation of Nickel-Based Superalloys Using Full-Field Digital Image Correlation and Infrared Thermography

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2163
Author(s):  
Krzysztof Żaba ◽  
Tomasz Trzepieciński ◽  
Sandra Puchlerska ◽  
Piotr Noga ◽  
Maciej Balcerzak
Keyword(s):  
Surface Temperature ◽  
Strain Rate ◽  
Rolling Direction ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Response Measurement ◽  
Sheet Rolling ◽  
Inconel Alloys ◽  
The Relationship

The paper is devoted to highlighting the potential application of the quantitative imaging technique through results associated with work hardening, strain rate and heat generated during elastic and plastic deformation. The aim of the research presented in this article is to determine the relationship between deformation in the uniaxial tensile test of samples made of 1-mm-thick nickel-based superalloys and their change in temperature during deformation. The relationship between yield stress and the Taylor–Quinney coefficient and their change with the strain rate were determined. The research material was 1-mm-thick sheets of three grades of Inconel alloys: 625 HX and 718. The Aramis (GOM GmbH, a company of the ZEISS Group) measurement system and high-sensitivity infrared thermal imaging camera were used for the tests. The uniaxial tensile tests were carried out at three different strain rates. A clear tendency to increase the sample temperature with an increase in the strain rate was observed. This conclusion applies to all materials and directions of sample cutting investigated with respect to the sheet-rolling direction. An almost linear correlation was found between the percent strain and the value of the maximum surface temperature of the specimens. The method used is helpful in assessing the extent of homogeneity of the strain and the material effort during its deformation based on the measurement of the surface temperature.

scholarly journals Optimization of Superplastic Forming Process of AA7075 Alloy for the Best Wall Thickness Distribution

2021 ◽  
Vol 6 (4) ◽  
pp. 251-261
Author(s):  
Manh Tien Nguyen ◽  
Truong An Nguyen ◽  
Duc Hoan Tran ◽  
Van Thao Le
Keyword(s):  
Wall Thickness ◽  
Deformation Temperature ◽  
Numerical Optimization ◽  
Thickness Distribution ◽  
Superplastic Forming ◽  
Forming Process ◽  
Wall Thickness Distribution ◽  
Surface Method ◽  
Series Of Experiments ◽  
The Relationship

This work aims to optimize the process parameters for improving the wall thickness distribution of the sheet superplastic forming process of AA7075 alloy. The considered factors include forming pressure p (MPa), deformation temperature T (°C), and forming time t (minutes), while the responses are the thinning degree of the wall thickness ε (%) and the relative height of the product h*. First, a series of experiments are conducted in conjunction with response surface method (RSM) to render the relationship between inputs and outputs. Subsequently, an analysis of variance (ANOVA) is conducted to verify the response significance and parameter effects. Finally, a numerical optimization algorithm is used to determine the best forming conditions. The results indicate that the thinning degree of 13.121% is achieved at the forming pressure of 0.7 MPa, the deformation temperature of 500°C, and the forming time of 31 minutes.

Enhancement of Superplastic Forming Limit of Magnesium Sheets by Counter-Pressurizing

2011 ◽  
pp. 385-387
Author(s):  
Wonkyu Bang ◽  
Hyun-Seok Lee ◽  
Hyung-Lae Kim ◽  
Young-Won Chang
Keyword(s):  
Superplastic Forming ◽  
Forming Limit

Cavity Nucleation in AL 5083 Alloys

1999 ◽  
Vol 601 ◽  
Author(s):  
N. Chandra ◽  
Z. Chen
Keyword(s):  
Electron Microscopy ◽  
Rolling Direction ◽  
Interfacial Strength ◽  
Superplastic Forming ◽  
Simplified Model ◽  
Hard Phase ◽  
Cavity Nucleation ◽  
Material Parameters ◽  
State Of Stress ◽  
Process Material

AbstractIn this paper we address the controversial issue of nucleation of cavities in Al 5083 alloys. We focus on the origin of cavities during the manufacture of these alloys into SPF (superplastic forming) sheet form. Experimental observations on the pre-existing cavities in this alloy are made using optical and electron microscopy. The effects of rolling direction and state of stress during superplastic deformations on the formation of cavities are also discussed. Numerical simulations of the sheet manufacturing process are carried out to understand the effect of hard phase/matrix, mechanical properties and interfacial strength on the origin of cavities. Based on the numerical results, a simplified model relating the process, material parameters and the cavity nucleation is presented.

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