Investigation of Superplastic Behavior of NiAI and Ni3Al Duplex Alloy

1996 ◽  
Vol 460 ◽  
Author(s):  
Liu Zhenyun ◽  
Lin Dongliang ◽  
T. L. Lin ◽  
Gu Yuefeng ◽  
Shan Aidang
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Superplastic Deformation ◽  
Empirical Equation ◽  
Tensile Elongation ◽  
Rate Sensitivity ◽  
Superplastic Behavior ◽  
Narrow Temperature Range ◽  
Optical Microstructure ◽  
Duplex Alloy

ABSTRACTThe superplastic behavior of a NiAI and Ni3Al duplex alloy was investigated. It was found that the alloy exhibits superplastic behavior over a narrow temperature range, from 975 °C to 1025°C at the strain rate of 1.52 × 10-4 s-1. A maximum tensile elongation of 149% was obtained at 1000°C with the strain rate sensitivity up to 0.375. The superplastic deformation of the duplex alloy can be approximately described by an empirical equation of the form: ε = Ao2.67 exp(-303,000 / RT). Optical microstructure and TEM observation show that the superplastic behavior mechanism of the investigated alloy is a process of continuous recovery and recrystallization during deformation.

Superplasticity of AlCoCrCuFeNi High Entropy Alloy

2012 ◽  
Vol 735 ◽  
pp. 146-151 ◽  
Author(s):  
Andrey V. Kuznetsov ◽  
Dmitry G. Shaisultanov ◽  
Nikita Stepanov ◽  
Gennady A. Salishchev ◽  
Oleg N. Senkov
Keyword(s):  
Particle Size ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
Tensile Ductility ◽  
Rate Sensitivity ◽  
Particle Growth ◽  
High Entropy Alloy ◽  
Superplastic Behavior ◽  
High Entropy ◽  
Elongation To Failure

An AlCoCrCuFeNi high entropy alloy was multiaxially isothermally forged at 950°C to produce a fine equiaxed structure with the average grain/particle size of ~1.5 µm. The forged alloy exhibited superplastic behavior in the temperature range of 800-1000°C. For example, during deformation at a strain rate of 10-3 s-1, tensile ductility increased from 400% to 860% when the temperature increased from 800°C to 1000°C. An increase in strain rate from 10-4 to 10-2 s-1 at T = 1000°C did not affect ductility: elongation to failure was about 800%. The strain rate sensitivity of the flow stress was rather high, m = 0.6, which is typical to the superplastic behavior. The equiaxed morphology of grains and particles retained after the superplastic deformation, although some grain/particle growth was observed.

Superplastic Behavior of B- and Gd-Containing β-Solidifying TiAl Based Alloy

2018 ◽  
Vol 385 ◽  
pp. 131-136
Author(s):  
Vitaliy Sokolovsky ◽  
Nikita Stepanov ◽  
Sergey Zherebtsov ◽  
Nadezhda Nochovnaya ◽  
Pavel Panin ◽  
...  
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Strain Rate Sensitivity ◽  
Phase Field ◽  
Rate Sensitivity ◽  
Maximum Strain ◽  
Superplastic Behavior ◽  
Β Phase ◽  
Refined Microstructure ◽  
Phase Fields

Mechanical behavior and microstructure evolution of the cast Ti-43.2Al-1.9V-1.1Nb-1.0Zr-0.2Gd-0.2B alloy were studied at temperatures from 1100 to 1250°С and strain rates in the range 0.001-1 s-1. Following phase fields (α2+γ), (α+γ), (α) and (α+β) during heating of alloy were revealed. Microstructure analysis after deformation and mechanical behavior allowed defining main processes of structure formation. Two temperature-strain rate conditions with pronounced superplastic behaviour were found: the first one corresponded to the (α2+γ)-phase field (1100°C), where the microstructure had mainly a lamellar morphology, and the second was associated with the (α+β)-phase field (1250°C), in which the α-phase dominated. At T=1100°C and έ=0.05 s-1the maximum strain rate sensitivitymwas of 0.40. At T=1250°C and έ=0.5 s-1the maximum strain rate sensitivitymwas of 0.59. In the (α2+γ)-phase field, superplastic behavior was associated with the transformation of the lamellar structure into globular one. In the (α+β)-phase field, it was due to the formation of a homogeneous refined microstructure during dynamic recrystallization. The relationship between coefficient m value and microstructure formed was discussed.

The Effect of Controlled Melt-Solidification on the Strain Rate Sensitivity of a Squeeze-Cast Hybrid-Reinforced Aluminum AA 6061 Matrix Composite

2015 ◽  
Vol 16 ◽  
pp. 1-16
Author(s):  
B.O. Malomo ◽  
O.O. Fadodun ◽  
K.M. Oluwasegun ◽  
A.T. Ogunbodede ◽  
S.A. Ibitoye ◽  
...  
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Matrix Composite ◽  
Deformation Behavior ◽  
Squeeze Casting ◽  
Volume Fraction ◽  
Tensile Elongation ◽  
Testing Machine ◽  
Rate Sensitivity ◽  
Cooling Rates

A framework based on the relationship between variations in cooling rates and volume fraction of reinforcements during solidification processing to enhance the deformation behavior of aluminum alloy AA6061 matrix composite produced with a hybrid system of reinforcements is investigated in this study. The aluminum matrix composite with 5 %, 10 % and 20 % volume fraction of reinforcements (Al2O3-SiC) was synthesized by infiltrating molten aluminum AA 6061 at a pouring temperature of 740 °C into prefabricated preforms of reinforcements at a pressure of 80 MPa, die preheat temperature of 300 °C and pressure holding time of 15 s using the squeeze casting method. By employing water jet spraying at the rate of 0.1, 0.2 and 0.3 kg/s and taking measurements using a K-type thermocouple, cooling rates were obtained in correspondence with varying volume fractions of reinforcements. The developed composites were sectioned and microstructural features were examined by optical microscopy. Tensile testing was conducted according to ASTM B557 standard using an MTS testing machine. It was observed that cooling rates decreased as the volume fraction of reinforcements was increased and the cooling time also increased accordingly during this process. With respect to deformation behavior, higher cooling rates are associated with an improvement in mechanical properties at 5 % and 10 % additions of hybrid reinforcement particles but this effect diminishes as the volume fraction of reinforcements was increased to 20 %. Also, the strain rate sensitivity (SRS) exponent increased considerably with strain rates and volume fraction of reinforcements, but the tensile elongation values decreased with increasing volume fraction of reinforcements; and the variations in these properties were most significant for samples containing 20% volume fraction of hybrid reinforcements.From the foregoing, it follows that an experimentally-determined optimal solidification range is critical to the enhancement of deformation parameters as the volume fraction of reinforcements is varied in a squeeze casting process.

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.

Superplastic Deformation Behavior of Spray Formed High Speed Tool Steel at 820°C

2007 ◽  
Vol 561-565 ◽  
pp. 91-94
Author(s):  
Can Dong Zhou ◽  
Jun Fei Fan ◽  
Hai Rong Le ◽  
Jing Guo Zhang
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
High Speed ◽  
Tensile Axis ◽  
Tensile Elongation ◽  
High Speed Steel ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Dislocation Creep

Being examined by tensile tests at 820°C with initial strain rates of 2.5×10-4 s-1, 5.0×10-3 s-1and 1.0×10-1 s-1, the hot-rolled spay formed high speed steel (SF-HSS) had superplastic properties. With έ=2.5×10-4 s-1and 5.0×10-3 s-1, the σ-ε curves indicate that there has occurred dynamic recrystallization at the later stage of deformation.The tensile elongation decreases monotonously with strain rate increasing. The strain rate sensitivity m =dlogσ/dlog έ is about 0.23. In the sub-surface of fractured SF-HSS samples with έ=2.5×10-4 s-1,, most of holes on the subsurface are observed to distribute near the carbides and arranged along the tensile axis direction. The interface between coarse carbides and matrix is very weak sites where the holes are easy to nucleate and connect to cracks during deformation. In the necked region, fine carbide particles on the grain boundary have pinned the slip of dislocations and formed dislocation wall inside the grain. Dynamic recrystallization and some climb of dislocations has occurred. The superplastic deformation mechanism with έ=2.5×10-4 s-1 was dislocation creep mechanism controlled by dynamic recrystallization. During deformation, the role of some carbide in the materials was to retard the grain growth and keep SF-HSS having fine equiaxed grain size and remain stable.

Effect of Hydrogen on the Superplastic Behavior of Ti-6Al-4V Alloy

1990 ◽  
Vol 196 ◽  
Author(s):  
B. Gong ◽  
C. B. Zeang ◽  
Z. H. Lai ◽  
Z. S. Xu
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Superplastic Behavior ◽  
Superplastic Behaviour

ABSTRACTThe superplastic behaviour of Ti-6Al-4V alloy containing various amounts of hydrogen (0.07 ∼ 0.33wt%) has been investigated by tensile tests at temperatures of 800 ∼ 950°C. Results show that the solution of hydrogen in the alloy helps to reduce the flow stress with strain rate in the range of 1.67 ×10−4 ∼ 1.67×10−2 s−1 and makes the temperature of superplastlc deformation become Lower (810∼870°C). Nevertheless, it also causes a decrease of the strain rate sensitivity exponent and tensileelongation, However, by a suitable alloying with hydrogen (∼ 0.1wt%), the alloy can be made to undergo superplastlc deformation at a rather tow temperature (840°C) with an acceptable loss of superptastic ductility.

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