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Alloying of two-phase alloy based on the Ti–Al–Mo–V system (VT14) with Fe and B makes it possible to obtain fine-grained structure, reduce β-transus and temperature equal volume fractions α and β phases, and as result, to decrease superplastic deformation temperature., В ходе работы было показано, что легирование двухфазного сплава на базе системы Ti–Al–Mo–V (ВТ14) добавками 0,1 %B и 1,8 %Fe позволяет получить ультрамелкозернистую структуру, понизить температуру β-трансуса и температуру равенства объемных долей α и β фаз, и, как следствие, снизить температурный интервал проявления сверхпластичности.

During grain boundary sliding in ultrafine-grain materials at intermediate temperatures and high strain rates (~10 s), apparent creep parameters usually deviate from the theoretical values, due to microstructural coarsening. An analysis has been carried out in a severely friction stir processed (FSP) 7075 alloy with three different ultra-fine grain sizes (L), obtaining explicit grain size dependence of the creep parameters n = n(L) and Q = Q(L), confirming the validity of the theoretical values of these parameters in the constitutive equation.

The 7075 Al alloy was processed by accumulative roll bonding (ARB) at 350 °C using 2:1, 3:1 and 4:1 thickness reductions per pass (R) up to 8, 6 and 3 passes, respectively. Microstructural examinations of the processed samples revealed that ARB leads to a microstructure composed of equiaxed crystallites with a mean size generally lower than 500 nm. It was found that, due to both the stored energy throughout the processing and the particle pinning effect, the alloy is affected by discontinuous recrystallisation during the inter-pass heating stages, the precise microstructural evolution being dependent on R. Mechanical testing of the ARBed samples revealed that the main active deformation mechanism in the ARBed samples in the temperature range from 250 to 350 °C at intermediate and high strain rates is grain boundary sliding, the superplastic properties being determined by both the microstructure after ARB and its thermal stability.

The high-temperature mechanical behavior of extruded Mg97-3x Y2x Zn x (at. pct) alloys is evaluated from 473 K to 673 K (200 C to 400 C). The microstructure of the extruded alloys is characterized by Long Period Stacking Ordered structure (LPSO) elongated particles within the magnesium matrix. At low temperature and high strain rates, their creep behavior shows a high stress exponent (n = 11) and high activation energy. Alloys behave as a metal matrix composite where the magnesium matrix transfers part of its load to the LPSO phase. At high-temperature and/or low stresses, creep is controlled by nonbasal dislocation slip. At intermediate and high strain rates at 673 K (400 C) and at intermediate strain rates between 623 K and 673 K (350 C and 400 C), the extruded alloys show superplastic deformation with elongations to failure higher than 200 pct. Cracking of coarse LPSO second-phase particles and their subsequent distribution in the magnesium matrix take place during superplastic deformation, preventing magnesium grain growth. © 2013 The Minerals, Metals & Materials Society and ASM International.

Quick Plastic Forming (QPF) is a recent adaptation of Superplastic Forming (SPE) that allows economical fabrication of complex components using superplastic material. QPF requires refined, equiaxed grains and high-angle grain boundaries in the microstructure to enhance sheet deformation by GBS at the high strain rates involved. This study evaluates the effects of laboratory rolling conditions on continuously cast AA5083 in the hot-band condition in anticipation of QPF., The original document contains color images.

This study evaluated dome test samples of a superplastic AA5083 aluminum alloy deformed at nominally constant strain rates under biaxial strain conditions. Dome test samples resulted from gas-pressure forming of sheet material; for this study, samples were deformed at strain rates corresponding either to grain boundary sliding or dislocation creep control of deformation. Orientation Imaging Microscopy was utilized to determine texture development, grain size and grain-to-grain misorientation angle distributions for locations located along a line of latitude of the dome samples. The goal was to identify the location of the transition from grain boundary sliding to dislocation creep. Grain boundary sliding, which dominates at lower strain rates, can be recognized by a randomized texture and a higher concentration of high disorientation angles. Dislocation creep, which dominates at higher strain rates, is characterized by fiber texture formation and development of a peak at lower angles in the grain-to-grain misorientation angle distribution., The original document contains color images.

At the time of initiation of this research, the materials community was just becoming aware of the pioneering work on nanophase materials by Prof. Gleiter, in Germany, and the forecasts of new materials with highly desirable properties were being offered. For ceramic materials, the potential for low temperature sintering and superplastic deformation were very exciting possibilities, while the effect of nanoscale grain structures on other properties were also of interest. This research, therefore, was initiated to evaluate the properties of monolithic, nanophase ceramic materials., The original document contains color images. All DTIC reproductions will be in black and white.

In previous work, the room temperature mechanical properties of an Al-10Mg-0.1Zr alloy were evaluated after simulated, superplastic forming at a temperature of 300 C (573K). A variation of ductility from 1 to 14% elongation was observed in the room temperature test data. To examine the cause of this variability, the processing schedule was changed to one incorporating more severe reductions during rolling. This resulted in a lesser range of variability in room temperature ductility, but the material no longe behaved superplastically. Elongations at 300 C of only 161% at a maximum were recorded although the small grain size required for good superplasticity apparently was developed. SEM and optical microscopy was then done to investigate the cause of this loss of superplastic behavior. Keywords: Superplasticity, Ductility, Aluminum magnesium, Alloys, thermomechanical, Processing, Aluminum alloys.

A ceramic-base material containing a matrix of 80% fine-grained iron carbide with 20 wt.% Fe, prepared from rapidly solidified powders, exhibited superplastic behaviour at elevated temperatures. High strain-rate-sensitivity exponents, m, of 0.5-0.7, were observed from 675-1000 deg C and at strain rates as high as 10 exp --2 s exp --1 . The fine-grained (3-4 mu m) material remained equiaxed, and exhibited no significant grain growth, after superplastic deformation. The ductility in the high m region was shown to be a strong function of temperature and strain rate, and to increase as the product epsilon exp(Qc/RT) decreased. This trend is associated with the increasing contribution of superplastic flow during grain boundary separation.

An Al-6%Mg -0.3%Sc-0.3%Mn alloy was subjected to equal-channel angular extrusion (ECAE) at 325⁰C to a total strain of about 16 that resulted in an average grain size of about 1 µm. Superplastic properties and microstructural evolution of the alloy were studied in tension at strain rates ranging from 1.4x10־⁵ to 1.4 s־¹ in the temperature interval from 250⁰ to 500⁰C, Belgorod State University

The hot deformation behaviors of the aluminium alloy PM2014 and metal matrix composite PM2014-20% Al₂O₃p, produced via powder metallurgy, have been compared by tension tests in the range of temperatures and strain rates of T=450-525°C and ε=10⁻¹⁴-1.1 s⁻¹ respectively, Belgorod State University

Experiments were conducted to evaluate the influence of zirconium and copper additions on superplastic behavior of a 6061 aluminum alloy. The results suggest the addition of Zr provides high stability of the fine-grained structure under superplastic deformation at high temperatures by precipitation of Al₃Zr dispersoids. Apparently, the increased amount of liquid phase caused by the copper addition can enhance the superplastic properties of the 6061 alloy, Belgorod State University

This study evaluated dome test samples of a superplastic AA5083 aluminum alloy deformed at nominally constant strain rates under biaxial strain conditions. Dome test samples resulted from gas-pressure forming of sheet material; for this study, samples were deformed at strain rates corresponding either to grain boundary sliding or dislocation creep control of deformation. Orientation Imaging Microscopy was utilized to determine texture development, grain size and grain-to-grain misorientation angle distributions for locations located along a line of latitude of the dome samples. The goal was to identify the location of the transition from grain boundary sliding to dislocation creep. Grain boundary sliding, which dominates at lower strain rates, can be recognized by a randomized texture and a higher concentration of high disorientation angles. Dislocation creep, which dominates at higher strain rates, is characterized by fiber texture formation and development of a peak at lower angles in the grain-to-grain misorientation angle distribution., http://archive.org/details/identificationof109451204, Ensign, United States Navy, Approved for public release; distribution is unlimited.

The aim of this study is to examine a modified processing route for the 2219 alloy, and the superplastic behavior of the processed alloy, Belgorod State University

Superplasticity in a 7055 aluminum alloy subjected to intense plastic straining through equal-channel angular extrusion (ECAE) was studied in tension over a range of strain rates from 1.4×10⁻⁵ to 5.6×10⁻¹ s⁻¹ in the temperature interval 300-450°C. The alloy had a grain size of ~1 µm. A maximum elongation-to-failure of ~750% appeared at a temperature of 425°C and an initial strain rate of 5.6×10⁻⁴ s⁻¹, where the strain rate sensitivity coefficient, m, was about 0.46, Belgorod State University

The possibility of superplastic deformation of ultrafine-grained materials is discussed in terms of the influence of grain boundary structure on mechanisms of superplastic flow, Belgorod State University

In the composite with uniform distribution of the whiskers the spacing between surfaces of CGBS in units of average matrix grain size is slightly less than in the another state of the composite. In addition, the occurrence of grain boundary sliding was observed to decrease. The origin of high strain rate superplasticity (HSRS) in metal matrix composites (MMC) is discussed, Belgorod State University

Comparing the present results with the superplastic behaviour of the 7055 Al subjected to thermomechanical processing (TMP), the highest tensile elongation in the ECAE processed material occurred at lower temperatures because ECAE produces a finer grained structure, Belgorod State University

Superplastic behavior of this alloy was examined in the temperature range 150-250°C at strain rates ranging from 1.4x10⁻⁵ to 5.6x10⁻² s⁻¹. The strain rate sensitivity was measured as ~0.32 at these conditions. This temperature is exceptionally low for superplasticity in Al-based alloys, as it has been reported to date. Features of superplastic deformation at such the low temperature are considered, Belgorod State University

The aim of the present work is to study the annealing behavior of a 304-type stainless steel with an ultra fine-grained microstructure, which was developed by warm multi-axial deformation, Belgorod State University

A specific objective of this work is to examine the microstructural evolution, cavitation, and fracture caused by high-strain-rate superplastic deformation, Belgorod State University

Grain structure and texture evolution during superplastic deformation were studied on the PM2014-20%Al2O3 metal matrix composite produced via a powder technology method. Samples were deformed in tension at different stwww.lw20.comrains in the range of true strain rates 10-4-100 s-1 at temperature T = 500° C. It was shown that in the initial stage of superplastic flow deformation bands are formed in the aluminum matrix along the tension direction, Belgorod State University

A novel commercial Al-Li-Mg-Cu-Sc alloy was fabricated by casting and subjected to intense plastic deformation through equal-channel angular extrusion at 598K to a total strain of ~16. The microstructure evolution and cavitation during superplastic deformation were examined, Belgorod State University

The data of microstructural observation and misorientation analysis show that low-angle boundaries (LAB) gradually convert to high-angle boundaries (HAB) resulting in an extensive flow softening. It was shown that grain boundary sliding (GBS) provides superplastic flow at all strains. Concurrently, GBS plays an important role in the dynamic evolution of new grains facilitating conversion of LABs to HABs, Belgorod State University

The superplastic properties of a cold-rolled Al±6Mg±0.3Sc alloy were studied at temperatures between 450 and 5608C and strain rates between 10⁻⁴ and 100⁰ s⁻¹. The alloy was observed to exhibit super- plasticity over wide temperature (475±5208C). It was found that the addition of Sc to Al±Mg alloys resulted in a uniform distribution of fine coherent Al₃Sc precipitates which effectively pinned subgrain and grain boundaries during static and dynamic recrystallization. In this paper, the microstructural evolution during superplastic deformation was systematically examined using both opti- cal and transmission electron microscopy, Belgorod State University