The Effect of Copper Content on the Dynamic Grain Growth in AL-Cu-Zr Systems

2007 ◽  
Vol 558-559 ◽  
pp. 803-809 ◽  
Author(s):  
Kasra Sotoudeh ◽  
Pete S. Bate ◽  
John F. Humphreys
Keyword(s):  
Strain Rate ◽  
Grain Growth ◽  
Copper Content ◽  
Texture Evolution ◽  
Uniaxial Tensile ◽  
Sensitivity Index ◽  
High Angle ◽  
Initial Microstructure ◽  
Dynamic Grain Growth ◽  
Effect Of Copper

The effect of copper content on dynamic grain growth in Al-Cu-Zr system was investigated by studying the microstructural development and texture evolution during uniaxial tensile deformation of Al-2wt%Cu-0.3wt.%Zr and Al-4wt%Cu-0.4wt.%Zr alloys at 450°C with a strain rate of 10-3s-1, with a similar initial microstructure in both materials. The initial microstructure consisted of layers of different orientations, the layers being separated by high-angle grain boundaries with low-angle boundaries separating grains within the layers. The initial grain spacing was about 5m and the texture was typical of rolled aluminium alloys. The 4wt.%Cu alloy gave a higher strain rate sensitivity index, m, and a greater ductility compared to the low copper content alloy. An increase in grain size occurred in both materials due to deformation, but this dynamic grain growth (DGG) was much greater in the material with the higher copper content. This was associated with a more rapid conversion of low-angle boundaries to high angle ones in the 4wt%Cu material which is consistent with changes in crystallographic texture occurring during deformation.

Tensile Deformation Behavior of 5A90 Al-Li Alloy Sheet at Elevated Temperature

2011 ◽  
Vol 66-68 ◽  
pp. 70-75 ◽  
Author(s):  
Gao Shan Ma ◽  
Song Yang Zhang ◽  
Han Ying Wang ◽  
Min Wan
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Deformation Behavior ◽  
Tensile Deformation ◽  
Alloy Sheet ◽  
Hot Forming ◽  
Uniaxial Tensile ◽  
Sensitivity Index ◽  
Tensile Deformation Behavior ◽  
Increasing Temperature

Uniaxial tensile deformation behavior of 5A90 aluminium-lithium alloy sheet is investigated in the hot forming with the temperature range of 200-450°C and strain rate range of 0.3×10-3-0.2×10-1s-1. It is found that the flow stress of 5A90 Al-Li alloy in uniaxial tension increase with increasing strain rate and decrease with increasing temperature, however, the tendency of total elongation is just the reverse, and the optimum forming temperature is 400°C. The strain rate sensitivity index (m-value) remarkably increases with increasing temperature for a given strain rate. It is shown that 5A90 Al-Li alloy sheet displays the sensitivity to the strain rate at elevated temperatures. For a given strain rate, the strain hardening index (n-value) decreases with increasing temperature, whereas the n-value increases above 350°C. The constitutive equation of stress, strain and strain rate for 5A90 Al-Li alloy at any temperature is obtained by fitting the experimental data, which gave a good flow stress model for the FEM simulation of hot forming.

The Effect of Strain Rate History on the Dynamic Grain Growth Behaviour of AA 5083

2007 ◽  
Vol 551-552 ◽  
pp. 627-632
Author(s):  
B. Zhang ◽  
Pete S. Bate ◽  
Norman Ridley
Keyword(s):  
Strain Rate ◽  
Grain Growth ◽  
Significant Influence ◽  
Mechanical Behaviour ◽  
Strain Rates ◽  
Growth Behaviour ◽  
Superplastic Behaviour ◽  
Dynamic Grain Growth

Dynamic grain growth in superplastic AA5083 deformed at constant strain rates and varying strain rates has been studied. It has been found that the strain rate history has a significant influence on the grain growth behaviour. It is proposed that differences in mechanical behaviour of AA5083 for the strain rate conditions examined can be attributed to differences in the grain growth behaviour. The influence of dynamic grain growth on the superplastic behaviour of AA5083 is discussed.

Instability of Superplastic Aluminium Alloys

1990 ◽  
Vol 196 ◽  
Author(s):  
H. Iwasaki ◽  
S. Hayami ◽  
K. Higashi ◽  
S. Tanimura
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Grain Growth ◽  
Aluminium Alloys ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
Plastic Instability ◽  
Small Magnitude ◽  
Instability Parameter ◽  
Dynamic Grain Growth

ABSTRACTThe influence of the strain hardening coefficient,γ,and the strain rate sensitivity exponent, m, on the onset and growth of necking has been pointed out in many models about plastic instability controlled by the mechanical properties of materials. In this paper, the instability parameter I (=(l-γ-m)/m) proposed by Hart is used to relate the values of m (=∂lnσ/∂lnέ) and γ (=∂σ/(σ·∂ε)) for some superplastic aluminium alloys. These values of m and γ were calculated from the load-elongation curve at various strain-rates in constant strain-rate tests with periodic m determinations by strain-rate departures of small magnitude. It will be shown that the strain hardening due to grain growth contributes to an increase in the stability of plastic deformation during superplastic flow. However the decrease of m due to dynamic grain growth with strain causes superplastic deformation to be unstable near the onset of fracture. The transition of I values from negative to positive coincides with a decrease in m value and flow stress.It is concluded that the development of necks can be characterized by an instability parameter I which include the effect of strain hardening caused by strain induced grain growth.

scholarly journals Superplastic Behavior of Al-Mg-Mn Alloy: An Experimental & Numerical Investigation

2018 ◽  
Vol 778 ◽  
pp. 45-52
Author(s):  
Tayyaba Zaman ◽  
Rehan Qayyume ◽  
Amjad Ali ◽  
Shaheed Khan ◽  
Chaoli Maa
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Deformation Mechanism ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Uniaxial Tensile ◽  
Sensitivity Index ◽  
Deformation Response ◽  
Surface Optical ◽  
Dominant Deformation Mechanism

Deformation response of Al-4.46Mg-0.48Mn alloy under uniaxial tensile loading was investigated at temperatures ranging from 400°C - 525°C and at strain rates of 3x10-3s-1, 1x 10-3s-1& 10-4s-1. The alloy exhibited a maximum elongation >480% at a strain rate of 10-3s-1and 525°C. At all conditions, the dominant deformation mechanism governing the superplastic deformation was investigated as a function of strain rate and temperature. The contributions of strain-rate sensitivity and strain hardening were analyzed in relation to the observed tensile ductility. The strain rate sensitivity index (m) and average activation energy (Q) values revealed that the dominant deformation mechanism is grain boundary sliding (GBS). The GBS phenomenon was further confirmed through high magnification examination of deformed surface. Optical microscopy (OM) and Scanning Electron Microscopy (SEM) showed that dynamic re-crystallization occurs during hot deformation of the alloy which causes reasonable enhancement of plasticity.

A Superplasticity Theory based on Dynamic Grain Growth

1999 ◽  
Vol 601 ◽  
Author(s):  
M.J. Mayo ◽  
J.R. Seidensticker
Keyword(s):  
Growth Rate ◽  
Strain Rate ◽  
Stress Exponent ◽  
Grain Growth ◽  
Linear Relation ◽  
Growth Strain ◽  
Mathematical Relationship ◽  
Rate Law ◽  
Dynamic Grain Growth

AbstractThe linear relation between dynamic grain growth rate and strain rate appears to be constant across all superplastic materials—regardless of whether the system examined is metallic or ceramic, and regardless of the stress exponent exhibited during deformation. The simplicity and universality of the dynamic grain growth law suggest it might be useful as a foundation for a theory for superplasticity. One attempt at such a theory is presented. It is argued that stress leads to the development of anisotropic grain shapes that then require recovery through directionally biased grain growth events. Once this mathematical relationship between stress and grain growth rate is developed, it is inserted into the existing dynamic grain growth - strain rate law to arrive at a phenomenological law for superplasticity.

scholarly journals Study on the Formability and Texture evolution of AA6061 Alloy Processed by Repetitive Corrugation and Straightening.

2021 ◽  
Vol 19 (5) ◽  
pp. 548-561
Author(s):  
Sergio Elizalde ◽  
Marco Ezequiel ◽  
José María Cabrera ◽  
Ignacio Alejandro Figueroa ◽  
María Teresa Baile ◽  
...  
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Texture Component ◽  
Texture Evolution ◽  
Cube Texture ◽  
Rate Sensitivity ◽  
Distribution Functions ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Ultrafine Grained

The enhanced mechanical properties obtained by refining the grain size down to the ultrafine-grained (UFG) regime have attracted considerable attention in recent years. The severe plastic deformation (SPD) techniques allow obtaining ultrafine-grained materials. Different SPD techniques permit processing sheet shape materials such as repetitive corrugation and straightening (RCS) and accumulative roll bonding (ARB). In this study, the formability of an AA 6061-T6 processed by RCS was evaluated. The forming limit diagrams (FLD) were obtained by Nakazima tests of samples in initial condition (T6 state) and after one and two RCS cycles. The FLD curves showed that the forming capacity decreased from the first RCS cycle. Likewise, uniaxial tensile tests at different temperatures and strain rates were conducted to analyze the effect of the RCS process on the strain rate sensitivity. They showed a relatively high strain rate sensitivity coefficient in the samples after one and two RCS cycles, which indicates an improvement of i) the capacity of the material to delay the onset of the necking and ii) the formability at increasing temperatures. Finally, texture analysis was carried out employing X-ray diffraction, calculating the orientation distribution functions (ODFs). The initial texture showed a predominant cube texture component, whereas, for further RCS cycles, a weakening of the cube texture and an increment of the S texture component were observed.

Determination of Material Parameters during Superplastic Forming of AZ31B Magnesium Alloy at Elevated Temperatures in Uniaxial Tensile Test

2015 ◽  
Vol 787 ◽  
pp. 437-441
Author(s):  
S. Ramesh Babu ◽  
Vijul Shah ◽  
M.P. Shyam
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Elevated Temperatures ◽  
Rate Sensitivity ◽  
Superplastic Forming ◽  
Uniaxial Tensile ◽  
Sensitivity Index ◽  
Percentage Elongation ◽  
Strain Rate Sensitivity Index

Superplasticity is the ability of the material to produce neck free elongations within a material before fracture. For the past three decades superplastic forming has gained a major development in many industries to produce complex shapes. To perform the superplastic forming at elevated temperatures, the material parameters such as strain rate and strain rate sensitivity index has to be determined. These parameters affect the formability in such a way that higher the strain rate during deformation, lesser will be the percentage elongation and which in turn increases the flow stress of the material there by limiting the formability. Similarly, the strain rate sensitivity index is a measure of resistance to neck formation during deformation. Lesser the strain rate sensitivity value, more will be the neck formation thereby limiting the formability. Hence in this work, an experimental setup is designed to perform the uniaxial tensile testing at elevated temperatures to determine the flow stress, percentage elongation, strain rate and strain rate sensitivity. The determination of these parameters will be helpful in executing the forming at certain temperature and pressure to attain maximum formability. Also the SEM photographs of the fractured specimen were analysed to determine at what temperature and strain rate, the cavitation density increases.

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