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A damping alloy with a nominal composition of 50Al–49.9Zn–0.1Ce (at%) was tested in hot compression (60% depression) using a Gleeble-3800 thermomechanical simulator at deformation temperatures and strain rates ranging from 573 to 648 K and 0.01 to 10 s−1, respectively. According to the true stress-strain curves, two constitutive equation models based on peak stress and strain compensation were constructed. The microstructure of the alloy after deformation was characterized and analyzed by means of X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that the flow stress increases with decreasing deformation temperature and increasing strain rate. The theoretical predictions of the constitutive equation model at low temperature and high strain rate are well fitted to the measured values with low average absolute relative errors. At low strain rates and high temperatures, the α + η eutectoid structure tends to transform from lamellar to granular morphologies, which is accompanied by the increased sizes of α and η phases. Also, the obvious dissolution of η into α phase has been occurred and some tiny holes induced by thermal-force coupling have been formed during compression. In this work, the Al–Zn–Ce damping alloy is more suitable for thermomechanical processing at relatively lower temperatures and meanwhile higher strain rates (such as at 573 K/0.1 s−1, 573 K/10 s−1 and 623 K/10 s−1). [ABSTRACT FROM AUTHOR]

The hot deformation process significantly affects the performance of the manufactured Zr alloy components in nuclear reactors. The hot deformation behavior of the Zr-1wt.% Nb alloy with an initial β-quenched microstructure was evaluated using hot compression test at the temperature range of 600-950 °C and the strain rate range of 0.001-0.8 s−1. The constitutive equation was determined using kinetic analysis. The strong effect of Nb on decreasing self-diffusion in Zr was the reason for the obtained large activation energy of 390 kJ/mol in the Zr-1Nb alloy. Based on the dynamic material model, the processing map was constructed at the strain of 0.8 to show the stable and unstable hot deformation regions. The microstructural features of the hot deformed samples were observed using optical and scanning electron microscopes. The results indicated that the hot deformed microstructures were fully recrystallized so that the grain size of the as-received microstructure of the Zr-1Nb alloy was reduced from 1 mm to less than 4 μm after hot deformation at 800 °C. The optimum region in the hot deformation of the Zr-1Nb alloy with dynamic recrystallized microstructure and the peak efficiency of 40% was located at the temperature range of 675-775 °C and the strain rate range of 0.001-0.01 s−1. On the other hand, flow localization and macro-surface cracking occurred within the strain rate range of 0.1-0.8 s−1. [ABSTRACT FROM AUTHOR]

Cu–9Ni–6Sn alloys have received widespread attention due to their good mechanical properties and resistance to stress relaxation in the electronic and electrical industries. The hot compression deformation behaviors of the Cu–9Ni–6Sn–0.3Mn–0.2Zn alloy were investigated using the Gleeble-3500 thermal simulator at a temperature range of 700–900 °C and a strain rate range of 0.001–1 s−1. The microstructural evolution of the Cu–9Ni–6Sn alloy during hot compression was studied by means of an optical microscope and a scanning electron microscope. The constitutive equation of hot compression of the alloy was constructed by peak flow stress, and the corresponding 3D hot processing maps were plotted. The results showed that the peak flow stress decreased with the increase in the compression temperature and the decrease in the strain rate. The hot deformation activation energy was calculated as 243.67 kJ/mol by the Arrhenius equation, and the optimum deformation parameters for the alloy were 740–760 °C and 840–900 °C with a strain rate of 0.001~0.01 s−1. According to Deform-3D finite element simulation results, the distribution of the equivalent strain field in the hot deformation samples was inhomogeneous. The alloy was more sensitive to the deformation rate than to the temperature. The simulation results can provide a guideline for the optimization of the microstructure and hot deformation parameters of the Cu–9Ni–6Sn–0.3Mn–0.2Zn alloy. [ABSTRACT FROM AUTHOR]

High-cycle fatigue (HCF) is a critical property of metastable β Ti alloys in aerospace applications. In this work, the HCF behavior and corresponding microscale deformation mechanisms of a metastable Ti-5Al-5Mo-5V-1Cr-1Fe (Ti55511) alloy with a basket-weave structure were investigated. HCF and its deformation mechanisms of a Ti55511 alloy were systematically studied in the deformed condition by using a scanning electron microscope (SEM), a transmission electron microscope (TEM), and electron backscatter diffraction (EBSD). It was found that the Ti55511 alloy exhibited an excellent HCF strength (107 cycles, Kt = 1, R = 0.06) of 738 MPa. The fractographic investigation demonstrated that fatigue striations and secondary cracks were the main features in the crack initiation zone. Dislocation analyses indicated that the HCF deformation of the basket-weave microstructure was mainly affected by the dislocation slipping of the primary α (αp) phase. In addition, the dislocation pile-up at the αp/βtrans interface led to crack initiation. EBSD analyses indicated that the prismatic type slip system of the αp phase was preferentially activated during the HCF deformation process of the Ti55511 alloy, followed by the basal type and pyramid type systems. [ABSTRACT FROM AUTHOR]

In this work a new nanoscale surface marking technique, namely electron beam damage induced surface marking (EBDISM), is developed and tested for the first time on a fine-grained pure Mg surface. This technique utilizes focused high-energy electron beam of a scanning electron microscope to "burn" dense arrays of nano-scale grid patterns on the sample surface, and it is proved to be very effective for identifying and measuring localised deformation behaviours. However, the surface marking deposited by EBDISM is not permanent and it tends to deteriorate overtime. Cheap, easy to use and versatile, the EBDISM technique has a huge potential for quantitative measurement of strain field and nano-scale deformation analysis. [ABSTRACT FROM AUTHOR]

A novel biomaterial Ti-17Mo (mass%) was designed for orthopedic implant applications. Hot working behavior and deformation characteristics were studied in the β-single structure by hot compression tests in the strain rate range 0.01–10 s−1 and temperature range 1123–1273 K using a Thermec Master-Z simulator. The microstructural evolutions of the deformed alloy were studied by a scanning electron microscope equipped with an electron backscattered diffraction detector. The microstructures of the hot deformed alloy showed that dynamic recovery was more active than dynamic recrystallization (DRX). However, partial discontinuous DRX by grain boundary bulging is activated at high temperatures and low strain rates, e.g., 1273 K and 0.01 s−1. Due to the high stacking fault energy of the β phase with a bcc structure, the Ti-17Mo alloy possessed comparatively low activation energy of hot deformation (283 kJ/mol) compared with the conventional Ti alloys bearing multiple alloying elements. [ABSTRACT FROM AUTHOR]

• The mechanical properties of microstructures depend on mesoscopic slip and fracture behavior. • There exist many long slip traces directly passing through the microtextured regions. • Blocked slip arouses a high stress concentration in microtextured region. • Slip transmission is related to alignment between two slip systems and their Schmidt factors. In this paper, the tensile behavior and deformation mechanism of two typical bimodal microstructures in Ti6242S alloy were investigated through the in-situ scanning electron microscope (SEM) test and electron backscatter diffraction (EBSD). The results showed that the two microstructures presented different mechanical properties due to the different microscopic slip and fracture behaviors. In the homogeneous microstructure (with homogeneous crystallographic orientation), most of the slip traces were restricted within the grains because the slip transmissions between neighboring grains were blocked. The slip deformation was relatively homogeneous. Therefore, the fracture mechanism was micro-void accumulation fracture. In the inhomogeneous microstructure (with many microtextured regions), there existed many long slip traces directly passing through the microtextured region (the region of α phase with similar crystallographic orientation), the slip behavior was closely related to the same basal slip. The blocked slip aroused a high stress concentration in microtextured region, which was easy to induce the formation of microcrack, and then the microcrack propagated along the slip band. This can be attributed to the fact that slip transmission behavior was closely related not only to the alignment between slip planes and slip directions in two neighboring slip systems , but also to their Schmidt factors (SFs). Thus, the fracture mechanism was the coexistence of micro-void accumulation facture and cleavage fracture. [ABSTRACT FROM AUTHOR]

Tensile ductility of the Ti-based composites, which consist of a β-Ti phase surrounded by ultrafine structured intermetallics, is tunable through the control of intermetallics. The two Ti-based alloys studied exhibit similar compressive yield strength (about 1000MPa) and strain (about 35%-40%) but show a distinct difference in their tensile plasticity. The alloy Ti71.8Nb14.1Ni7.4Al6.7 fractures at the yield stress while the alloy Ti71.8Nb14.1Co7.4Al6.7 exhibits about 4.5% of tensile plastic deformation. To clarify the effect of microstructure on the deformation behavior of these alloys, tensile tests were carried out in the scanning electron microscope. It is shown that the distribution as well as the type of intermetallics affects the tensile ductility of the alloys. [ABSTRACT FROM AUTHOR]

In this study, a Mg-9Gd-4Y-2Zn-0.5Zr (wt.%) alloy was subjected, after solution treatment, to hot compression deformation at different temperatures (350 °C, 400 °C and 450 °C) and different strain rates (0.001 s−1, 0.01 s−1, 0.1 s−1 and 0.5 s−1) on a Gleeble-3800 thermal simulator. The evolution of the stress–strain curves under different conditions was compared. The changes in microstructure caused by the different deformation parameters and the change law of the long-period stacking-ordered (LPSO) phase during compression were observed and analyzed by optical microscope (OM) and scanning electron microscope (SEM). The results show that with the increase in the deformation temperature and the decrease in the strain rate, the degree of dynamic recrystallization (DRX) gradually increased, and the morphology of the phase also changed through, for example, twist fracture. The continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) mechanisms activated during the thermal deformation process can effectively refine the grains and weaken the texture in the alloy. [ABSTRACT FROM AUTHOR]

The effect of small molybdenum additions, 0.66 and 2.3 at. pct, on the microstructure, tensile, and creep behavior of a nominally Ti-24A1-17Nb (at. pct) alloy was investigated. The alloy containing 2.3 at. pct Mo contained higher body-centered-cubic (bcc) phase volume fractions, which was expected as Mo stabilizes the bcc phase. Constant load, tensile-creep experiments were performed in the stress range of 29 to 275 MPa and the temperature range of 650 °C to 710 °C, in both air and vacuum environments. In-situ creep experiments were performed inside a scanning electron microscope chamber in order to identify the deformation evolution from surface observations. From these experiments, it was evident that α[sub2] intergranular cracking was prevalent and initiated the fracture process where the crack Path followed the α[sub2] grain boundaries. The Ti-24A1-17Nb-2.3Mo (at. pct) alloy exhibited significantly lower creep rates than the Ti-24A1-17Nb-0.66Mo (at. pct) alloy, and this was associated with less contiguity of the α[sub2] phase. [ABSTRACT FROM AUTHOR]

Cryogenic deformation can improve the strength and plasticity of Al–Li alloy, although the underlying mechanism is still not yet well understood. The effects of cryogenic temperature on the tensile properties and microstructure of an Al–Cu–Li alloy were investigated by means of tensile property test, roughness measurement, scanning electron microscope (SEM), optical microscope (OM), electron backscatter diffraction (EBSD), and transmission electron microscope (TEM). The results indicated that the strength and elongation of the as-annealed (O-state) and solution-treated (W-state) alloys increased with the decrease in deformation temperature, where the increasing trend of elongation of the W-state alloy was more significant than that of the O-state alloy. In addition, a temperature range was observed at approximately 178 K that caused the strength of the W-state alloy to slightly decrease. The decrease in temperature inhibited the dynamic recovery of the Al–Cu–Li alloy, which increased the dislocation density and the degree of work hardening, thus improving the strength of the alloy. At cryogenic temperatures, the internal grain structure was more involved in the deformation and the overall deformation was more uniform, which caused the alloy to have higher plasticity. This study provides a theoretical basis for the cryogenic forming of Al–Li alloy. [ABSTRACT FROM AUTHOR]