scholarly journals Micromechanisms of Fracture of Magnesium Based Composite After Superplastic Deformation

2016 ◽  
Vol 16 (2) ◽  
pp. 117-122 ◽  
Author(s):  
Beáta Ballóková ◽  
Katarína Sülleiová ◽  
Michal Besterci ◽  
Oksana Velgosová ◽  
Song-Jeng Huang
Keyword(s):  
Statistical Analysis ◽  
Elevated Temperature ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
Strain Rates ◽  
Significant Growth ◽  
Micromechanisms Of Fracture ◽  
Maximum Value

Abstract The micromechanisms of fracture of AZ61 + 1 wt. % Al2O3 composite in the zone of superplastic deformation was analysed and quantified in this work. The specimens were tested at temperature of 200°C at different strain rates. Changing the strain rate, from 1x10-2 s-1 to 1x10-4 s-1, a significant growth of ductility was observed. At maximum value of superplasticity the fracture was transcrystalline ductile with dimples of two size categories. Based on the statistical analysis of fracture micromechanisms at the elevated temperature and strain rates of 10-0- 1x10-4 s-1 hyperbolic dependency was depicted according to Gurland - Plateau theory.

scholarly journals INFLUENCE OF TEMPERATURE AND STRAIN RATE ON SUPERPLASTICITY KINETICS OF COMPOSITE AZ61-F MAGNESIUM MATERIALS

2018 ◽  
Vol 24 (3) ◽  
pp. 200
Author(s):  
Michal Besterci ◽  
Song-Jeng Huang ◽  
Katarína Sülleiová ◽  
Beáta Ballóková
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
Strain Rates ◽  
Maximum Strain ◽  
Influence Of Temperature ◽  
Angular Pressing ◽  
Micromechanisms Of Fracture ◽  
The Mean ◽  
Kinetics Of

Micromechanisms of fracture of AZ61-F composites in the zone of quasi-superplastic deformation were analyzed and quantified in this work. Deformation of AZ61-F magnesium alloys with 1 wt.% of Al<sub>2</sub>O<sub>3</sub> phase was tested at a temperature of 473 K and different strain rates. It was shown that at the temperature of 473 K and the highest strain rate applied from 1<em>× </em>10<em><sup>−</sup></em><sup>2</sup> to 1 <em>× </em>10<em><sup>−</sup></em><sup>4</sup> s<em><sup>−</sup></em><sup>1</sup>, a significant growth of ductility was observed. The mean dimples diameter of the ductile fracture decreased with the decreasing strain rate. The grain size of 0.7 μm was reached by severe plastic deformation using equal channel angular pressing (ECAP). Secondary Mg<sub>17</sub>Al<sub>12</sub> and Al<sub>2</sub>O<sub>3</sub> phases were identified. The maximum strain was reached at the temperature of 473 K and strain rate of 1 <em>× </em>10<em><sup>−</sup></em><sup>4</sup> s<em><sup>−</sup></em><sup>1</sup>.

scholarly journals High Strain Rate Superplasticity in Al-Zn-Mg-Based Alloy: Microstructural Design, Deformation Behavior, and Modeling

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2098 ◽  
Author(s):  
Olga Yakovtseva ◽  
Maria Sitkina ◽  
Ahmed O. Mosleh ◽  
Anastasia Mikhaylovskaya
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
High Strain ◽  
Flow Behavior ◽  
Constant Strain Rate ◽  
Superplastic Forming ◽  
High Strength ◽  
Strain Rate Range ◽  
Strain Rates

Increasing the strain rate at superplastic forming is a challenging technical and economic task of aluminum forming manufacturing. New aluminum sheets exhibiting high strain rate superplasticity at strain rates above 0.01 s−1 are required. This study describes the microstructure and the superplasticity properties of a new high-strength Al-Zn-Mg-based alloy processed by a simple thermomechanical treatment including hot and cold rolling. The new alloy contains Ni to form Al3Ni coarse particles and minor additions of Zr (0.19 wt.%) and Sc (0.06 wt.%) to form nanoprecipitates of the L12-Al3 (Sc,Zr) phase. The design of chemical and phase compositions of the alloy provides superplasticity with an elongation of 600–800% in a strain rate range of 0.01 to 0.6/s and residual cavitation less than 2%. A mean elongation-to-failure of 400% is observed at an extremely high constant strain rate of 1 s−1. The strain-induced evolution of the grain and dislocation structures as well as the L12 precipitates at superplastic deformation is studied. The dynamic recrystallization at superplastic deformation is confirmed. The superplastic flow behavior of the proposed alloy is modeled via a mathematical Arrhenius-type constitutive model and an artificial neural network model. Both models exhibit good predictability at low and high strain rates of superplastic deformation.

Uniaxial Compressive Strengths of Artificial Freshwater Ice

2011 ◽  
Vol 243-249 ◽  
pp. 4634-4637 ◽  
Author(s):  
Li Min Zhang ◽  
Zhi Jun Li ◽  
Qing Jia ◽  
Guang Wei Li ◽  
Wen Feng Huang
Keyword(s):  
Compressive Strength ◽  
Strain Rate ◽  
Uniaxial Compression Test ◽  
Strain Rates ◽  
Precise Control ◽  
Freshwater Ice ◽  
Ice Surface ◽  
Loading Direction ◽  
Maximum Value ◽  
Lower Strain

The uniaxial compression test was performed on artificial freshwater ice with a precise control-temperature unit compression tester of ice under -5, -10, -15, -20 and-30°C temperatures and strain rates ranging from 10-8 to 10-2 s-1. The loading direction was parallel to ice surface. The results showed that the compressive strength was very sensitive to the strain-rate. The uniaxial compressive strengths reached the maximum value at the ductile-brittle transition region, and the region was gradually close to the lower strain-rate with the decreasing temperature of test. Both the strain-rate and uniaxial compressive strength dependences could be expressed in terms of power function in the relevant ductile range of strain-rate. The tests also revealed that failure stress of ice increases with decreasing of temperature at the same strain rate.

The Influence of Microstructure on Superplastic Behaviours of γ-TiAl Alloys

1998 ◽  
Vol 552 ◽  
Author(s):  
J. Sun ◽  
J. S. Wu ◽  
G. X. Hu ◽  
Y. H. He ◽  
B. Y. Huang
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
Maximum Elongation ◽  
Tial Alloys ◽  
Different Temperatures ◽  
Incremental Strain

ABSTRACTIn this work, superplastic behaviours in Ti-33A1–3Cr-0.5Mo (wt%) γ-TiAl alloys with two different initial microstructures of near gamma (NG) and duplex (DM) structure were investigated with respect to the effect of testing temperatures and strain rates. At 1050°C and a strain rate of 8×10–5 S–1, a maximum elongation of 570% was observed for NG-TiAl and a maximum elongation of 467% for DM-TiAl. The relations of flow stress and strain rate sensitivity vs. strain rates at different temperatures were also determined by incremental strain rate tests. The results showed that the value of strain rate sensitivity is higher and the flow stress is lower for NG than those for DM at the same condition. The microstructural evolution during superplastic deformation was examined and correlated to the mechanical properties for these two alloys. The influence of microstructure on the superplastic behaviours of γ-TiAl alloys, and possible superplastic deformation mechanisms were finally discussed.

High Strain Rate Mechanical Properties of SAC-Q With Sustained Elevated Temperature Storage at 100 °C

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Pradeep Lall ◽  
Vishal Mehta ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Elevated Temperature ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Strain Rates ◽  
Electronic Components ◽  
High Aging Temperature ◽  
Fine Pitch ◽  
Duration Of Storage ◽  
Operating Temperatures

Abstract Leadfree electronics in harsh environments often may be exposed to elevated temperature for the duration of storage, transport, and usage in addition to high strain rate triggering loads during drop-impact, vibration, and shock. These electronic components may get exposed to high strain rates of 1 to 100 s−1 and operating temperatures up to 200 °C in critical surroundings. Doped SAC solder alloys such as SAC-Q are being considered for use in fine-pitch electronic components. SAC-Q consists of Sn-Ag-Cu alloy in addition to Bi (SAC+Bi). Prior data presented to date for lead-free solders, such as SAC-Q alloy, at high aging temperature and high strain rate are for 50 °C sustained exposure. In this paper, the effect of sustained exposure to temperature of 100 °C on high strain rate properties of SAC-Q is studied. Thermally aged SAC-Q samples at 100 °C have been tested at a range of strain rates including 10, 35, 50, and 75 s−1 and operating temperatures ranging from 25 °C up to 200 °C. Stress–strain curves are established for the given range of strain rates and operating temperatures. Also, the computed experimental results and data have been fitted to the Anand viscoplasticity model for SAC-Q for comparison.

Effect of Isothermal Aging and High Strain Rate on Material Properties of Innolot

2013 ◽  
Author(s):  
Pradeep Lall ◽  
Geeta Limaye ◽  
Sandeep Shantaram ◽  
Jeff Suhling
Keyword(s):  
Elevated Temperature ◽  
High Strain Rate ◽  
Strain Rate ◽  
Material Properties ◽  
Isothermal Aging ◽  
High Strain ◽  
Image Correlation ◽  
Lead Free ◽  
Strain Rates ◽  
Full Field

Industry migration to lead-free solders has resulted in a proliferation of a wide variety of solder alloy compositions. The most popular amongst these are the Tin-Silver-Copper (Sn-Ag-Cu or SAC) family of alloys like SAC105, SAC305 etc. Recent studies have highlighted the detrimental effects of isothermal aging on the material properties of these alloys. SAC alloys have shown up to 50% reduction in their initial elastic modulus and ultimate tensile strength within a few months of elevated temperature aging. This phenomenon has posed a severe design challenge across the industry and remains a road-block in the migration to Pb-free. Multiple compositions with additives to SAC have been proposed to minimize the effect of aging and creep while maintaining the melting temperatures, strength and cost at par with SAC. Innolot is a newly developed high-temperature, high-performance lead-free substitute by InnoRel™ targeting the automotive electronics segment. Innolot contains Nickel (Ni), Antimony (Sb) and Bismuth (Bi) in small proportions in addition to Sn, Ag and Cu. The alloy has demonstrated enhanced reliability under thermal cycling as compared to SAC alloys. In this paper, the high strain rate material properties of Innolot have been evaluated as the alloy ages at an elevated temperature of 50°C. The strain rates chosen are in the range of 1–100 per-second which are typical at second level interconnects subjected to drop-shock environments. The strain rates and elevated aging temperature have been chosen also to correspond to prior tests conducted on SAC105 and SAC305 alloys at this research center. This paper presents a comparison of material properties and their degradation in the three alloys — SAC105, SAC305 and Innolot. Full field strain measurements have been accomplished with the use of high speed imaging in conjunction with Digital Image Correlation (DIC). Ramberg-Osgood non-linear model parameters have been determined to curve-fit through the experimental data. The parameters have been implemented in Abaqus FE model to obtain full-field stresses which correlates with contours obtained experimentally by DIC.

A Study on the Evolution of the High Strain Rate Mechanical Properties of SAC105 Leadfree Alloy at High Operating Temperatures

2015 ◽  
Author(s):  
Pradeep Lall ◽  
Vikas Yadav ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperature ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Lead Free ◽  
Electronic Systems ◽  
Strain Rates ◽  
High Strain Rates ◽  
Solder Interconnects

Electronics products may often be exposed to high temperature during storage, operation and handling in addition to high strain rate transient dynamic loads during drop-impact. Electronics subjected to drop-impact, shock and vibration may experience strain rates of 1–100 per sec. There are no material properties available in published literature at high strain rate at elevated temperature. High temperature and vibrations can contribute to the failures of electronic system. The reliability of electronic products can be improved through a thorough understanding of the weakest link in the electronic systems which is the solder interconnects. The solder interconnects accrue damage much faster when subjected to Shock and vibration at elevated temperatures. There is lack of fundamental understanding of reliability of electronic systems subjected to thermal loads. Previous studies have showed the effect of high strain rates and thermal aging on the mechanical properties of leadfree alloys including elastic modulus and the ultimate tensile strength. Extended period of thermal aging has been shown to affect the mechanical properties of lead free alloys including elastic modulus and the ultimate tensile strength at low strain rates representative of thermal fatigue [Lee 2012, Motalab 2012]. Previously, the microstructure, mechanical response and failure behavior of leadfree solder alloys when subjected to elevated isothermal aging and/or thermal cycling [Darveaux 2005, Ding 2007, Pang 2004] have been measured. Pang [1998] has showed that young’s modulus and yield stress of Sn-Pb are highly depending on strain rate and temperature. The ANAND viscoplastic constitutive model has been widely used to describe the inelastic deformation behavior of solders in electronic components. Previously, Mechanical properties of lead-free alloys, at different high strain rates (10, 35, 50, 75 /sec) and elevated temperature (25 C-125 C) for pristine samples have been studied [Lall 2012 and Lall 2014]. Previous researchers [Suh 2007 and Jenq 2009] have determined the mechanical properties of SAC105 at very high strain rate (Above 1000 per sec) using compression testing. But there is no data available in published literature at high strain rate and at elevated temperature for aged conditions. In this study, mechanical properties of lead free SAC105 has been determined for high strain rate at elevated temperature for aged samples. Effect of aging on mechanical properties of SAC105 alloy a high strain rates has been studied. Stress-Strain curves have been plotted over a wide range of strain rates and temperatures for aged specimen. Experimental data for the aged specimen has been fit to the ANAND’s viscoplastic model. SAC105 leadfree alloys have been tested at strain rates of 10, 35, 50 and 75 per sec at various operating temperatures of 50°C, 75°C, 100°C and 125°C. The test samples were exposed to isothermal aging conditions at 50°C for different aging time (30, 60, and 120 Days) before testing. Full-field strain in the specimen have been measured using high speed imaging at frame rates up to 75,000 fps in combination with digital image correlation. The cross-head velocity has been measured prior-to, during, and after deformation to ensure the constancy of cross-head velocity.

Heat Treatment of Ti2AlNb Intermetallic and its Superplastic Properties

2007 ◽  
Vol 551-552 ◽  
pp. 453-456 ◽  
Author(s):  
He Ping Guo ◽  
Zhi Qiang Li
Keyword(s):  
Heat Treatment ◽  
Elevated Temperature ◽  
Strain Rate ◽  
Hot Rolling ◽  
Superplastic Deformation ◽  
Volume Fraction ◽  
Grain Structure ◽  
Maximum Elongation ◽  
Superplastic Properties ◽  
Equiaxed Grain

Ti2AlNb orthorhombic alloys exhibit great potential as advanced aerospace and structural materials serviced at elevated temperature. In this paper, pre-heat treatment of as-received hot rolling Ti-22Al-25Nb alloy was conducted. Fine, stable and equiaxed grain structure was obtained by the pre-heat treatment. The volume fraction of B2 increased when annealing at 980°C. The Ti-22Al-25Nb alloy showed characteristics of superplastic deformation when tested at 960°C. Maximum elongation of 280% has been obtained at strain rate of 1.0×10-4s-1.

High Strain Rate Mechanical Properties of SAC-Q With Sustained Elevated Temperature Storage at 100°C

2019 ◽  
Author(s):  
Pradeep Lall ◽  
Vishal Mehta ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Elevated Temperature ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Strain Rates ◽  
Electronic Components ◽  
High Aging Temperature ◽  
Fine Pitch ◽  
Duration Of Storage ◽  
Operating Temperatures

Abstract Leadfree electronics in harsh environments may often be exposed to elevated temperature for the duration of storage, process and usage in addition to high strain rate triggering loads during drop-impact, vibration and shock. These electronic components may get exposed to high strain rates of 1 to 100 per seconds and operating temperature up to 200°C in the critical surroundings. SAC solder alloys (e.g. SAC-Q (CYCLOMAX), and Innolot) are being considered for use in fine-pitch electronic components. SAC-Q consists of Sn-Ag-Cu alloy in addition to Bi (SAC+Bi). The data presented till date for lead-free solders like SAC-Q alloy at high aging temperature and at high strain rate are for 50°C sustained exposure. In this paper, effect of sustained exposure of 100°C on high strain rate properties of SAC-Q is studied. Thermally aged SAC-Q samples at 100°C have been tested at a range of strain rates including 10, 35, 50, and 75 per second and operating temperatures starting from 25°C up to 200°C. Stress-strain curves are established for the given range of strain rates and operating temperatures. Also, the computed experimental results and data have been fit to the Anand Viscoplasticity model for SAC-Q for comparison.

Automated procedures for the determination of high temperature viscoplastic damage constitutive equations

1992 ◽  
Vol 437 (1901) ◽  
pp. 527-544 ◽  
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Strain Rate ◽  
Cyclic Plasticity ◽  
Parameter Determination ◽  
Nominal Composition ◽  
Strain Rates ◽  
Material Parameters ◽  
The Matrix

Methods have been developed for the determination of the material parameters in the Chaboche viscoplasticity model, and in the evolution equation for cyclic plasticity damage. The matrix of cyclic plasticity tests required for parameter determination consists of nine tests to be carried out for three strain ranges, and for each strain range, three strain rates. A programme of uni-axial cyclic plasticity tests has been carried out on cast copper (nominal composition: 99.99% Cu, 0.005% O 2 , B. S. 1035-1037) at strain ranges ± 0.3%, ± 0.6%, and ± 1.0%, each at strain rates 0.6% s -1 , 0.06% s -1 , and 0.006% s -1 . The matrix of tests has been carried out at each of the following temperatures: 20, 50, 150, 250 and 500 °C. At elevated temperature, strain rate has been found to have a significant effect on specimen lifetime. Low strain rates lead to increased creep damage evolution at high temperature, and hence lead to reduced cycles to failure. Cast copper has been found to be a rate sensitive material at temperatures above 150 °C. No strain rate effect was observed at temperatures below 150 °C. Ratchetting tests have been carried out at 20, 150, 250 and 500 °C. The effect of mean stress and stress rate on ratchet rates and lifetimes has been examined. Mean stresses of the order of 1 % of the applied stress range have been found to lead to significant ratchet rates for this material, resulting in failure by plastic collapse at elevated temperature. The methods presented for the determination of the material parameters and the results of the cyclic plasticity testing programme have enabled the viscoplastic damage model to be developed.

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