EBSD study of superplastically strained Al-Mg-Li alloy

In this study, electron back scatter diffraction (EBSD) was employed to examine the microstructure evolved during superplastic deformation of advanced Al-Mg-Li alloy. In contrast to the widelyaccepted conception of superplasticity, the microstructure was found to be characterized by elongated grains, a notable fraction of low-angle boundaries, and a distinct (though a very weak) crystallographic texture. All these observations suggested a significant activity of intragranular sli

Superplastic behavior of fine-grained Al-Mg-Li alloy

The superplastic behavior of fine-grained 1420 Al-Mg-Li alloy was investigated using a modern electron microscopy technique based on automatic analysis of electron backscattered diffraction patterns (EBSD analysis

EBSD study of superplasticity: New insight into a well-known phenomenon

Electron backscatter diffraction (EBSD) was applied to investigate the superplastic behavior of a fine-grain Al-Mg-Li alloy. It was found that microstructural changes were noticeably influenced by the occurrence of continuous dynamic recrystallization. This mechanism involved a transverse subdivision of pre-elongated grains which eventually transformed into chains of nearly-equiaxed grain

EBSD characterization of cryogenically rolled type 321 austenitic stainless steel

Electron backscatter diffraction was applied to investigate microstructure evolution during cryogenic rolling of type 321 metastable austenitic stainless steel. As expected, rolling promoted deformation-induced martensitic transformation which developed preferentially in deformation bands. Because a large fraction of the imposed strain was accommodated by deformation banding, grain refinement in the parent austenite phase was minima

Annealing behavior of cryogenically-rolled Cu-30Zn brass

The static-annealing behavior of cryogenically-rolled Cu-30Zn brass over a wide range of temperature (100-900 °C) was established. Between 300 and 400 °C, microstructure and texture evolution were dominated by discontinuous recrystallization. At temperatures of 500 °C and higher, annealing was interpreted in terms of normal grain growth. The recrystallized microstructure developed at 400 °C was ultrafine with a mean grain size of 0.8 μm, fraction of high-angle boundaries of 90 pct., and a weak crystallographic texture

EBSD study of superplastically strained Al-Mg-Li alloy

In this study, electron back scatter diffraction (EBSD) was employed to examine the microstructure evolved during superplastic deformation of advanced Al-Mg-Li alloy. In contrast to the widely-accepted conception of superplasticity, the microstructure was found to be characterized by elongated grains, a notable fraction of low-angle boundaries, and a distinct (though a very weak) crystallographic texture. All these observations suggested a significant activity of intragranular slip

Microstructure evolution and some properties of hard magnetic FeCr30Co8 alloy subjected to torsion combined with tension

The hard magnetic alloy FeCr30Co8 alloy was subjected to severe plastic deformation (SPD) by torsion combined with tension in the temperature range of 750 °C to 850 °C. This range of deformation temperatures corresponds to the α solid solution on the Fe–Cr–Co phase diagram. The study of the alloy after SPD by means of X-ray diffraction (XRD) and scanning and transmission electron microscopy techniques showed the formation of a gradient microstructure with fine grain size in the surface layer and precipitation of the hard intermetallic σ-phase. Next, the magnetic and mechanical properties of the deformed alloy after short annealing at 1000 °C and magnetic treatment were studied. A slight decrease in coercive force was found, along with a significant gain in plasticity and strength. The effective deformation temperature was determined to obtain the optimal magnetic and mechanical characteristics of the alloy. This method of deformation can be applied for the improvement of the mechanical properties of some magnets (high-speed rotors) which should have good magnetic properties within their volume while maintaining good mechanical properties on the surfac

EBSD investigation of microstructure evolution during cryogenic rolling of type 321 metastable austenitic steel

Electron backscatter diffraction (EBSD) was employed to establish microstructure evolution in type 321 metastable austenitic stainless steel during rolling at a near-liquid-nitrogen temperature. A particular emphasis was given to evaluation of microstructure-strength relationship.As expected, cryogenic rolling promoted strain-induced martensite transformation. The transformation was dominated by the γ→α′ sequence but clear evidence of the γ→ε→α′ transformation path was also found. The martensitic reactions were found to occur almost exclusively within deformation bands, i.e., the most-highly strained areas in the austenite. This prevented a progressive development of deformation-induced boundaries and thus suppressed the normal grain-subdivision process in this phase. On the other hand, the preferential nucleation of martensite within the deformation bands implied a close relationship between the transformation process and slip activity in parent austenite grains. Indeed, the martensite reactions were found to occur preferentially in austenite grains with crystallographic orientations close to Goss {110} and Brass {110}. Moreover, the martensitic transformations were governed by preferential variant selection which was most noticeable in ε-martensite. The sensitivity of the martensitic reactions to the crystallographic orientation of the austenite grains resulted in re-activation of the transformation process after development of a deformation-induced texture in the austenitic phase at high strains. Both martensitic phases were concluded to experience plastic strain which resulted in measurable changes in misorientation distributions. Cryogenic rolling imparted dramatic strengthening resulting in a more-than-sixfold increase in yield strength. The main source of hardening was the martensitic transformation with lesser contributions from dislocations and subboundary strengthening of the austenite

Microstructure response of cryogenically-rolled Cu-30Zn brass to electric-current pulsing

The effect of transient electric-current pulses (ECP) on the evolution of microstructure and texture of cryogenically-rolled Cu-30Zn brass was determined. The pulsing was shown to lead to recrystallization followed by grain growth. The mean grain size in the recrystallized material was 0.5 μm, thus indicating that cryogenic rolling coupled with ECP is suitable for the production of an ultrafine-grain microstructure in Cu-30Zn brass. The differences in the recrystallization texture in pulsed versus statically-annealed conditions suggested a distinct recrystallization mechanism during ECP

Temperature and strain rate dependence of microstructural evolution and dynamic mechanical behavior in nanocrystalline Ti

The mechanical behavior of commercial purity titanium with a nanocrystalline (NC) grain size was investigated using split Hopkinson pressure bar tests at high strain rates and over a range of temperatures. The study was accompanied by detailed microstructural investigations before and after compression testing. The results show that rotary dynamic recrystallization operates during compressive deformation at strain rates of ~3000 and ~4500 s?1 at temperatures from 298 to 573 K but cells form at 673 K. The dynamic mechanical behavior of NC Ti shows a strong dependence on temperature and strain rate such that the flow stress and the strain hardening rate both increase with increasing strain and decreasing temperature. A constitutive equation is derived to relate the flow stress to the temperature, strain rate and true strain and to predict the yield strength and the peak stress of NC Ti subjected to dynamic deformation at elevated temperatures