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In this study, microstructure and texture evolution of TB8 titanium alloys during hot deformation were investigated by using electron back-scattered diffraction (EBSD) analysis. The results showed that dynamic recrystallization (DRX) behavior of TB8 titanium alloys was drastically sensitive to the strain. As the true strain raised from 0.2 to 0.8, the degree of DRX gradually increased. The nucleation mechanism of recrystallization was observed, including discontinuous dynamic recrystallization (DDRX) resulting from the bulging of original boundaries. Furthermore, continuous dynamic recrystallization (CDRX) occurred because of the transformation of low-angle grain boundaries (LAGBs) to high-angle grain boundaries (HAGBs) in the interior of the original deformed grains. The texture evolution of TB8 titanium alloy during hot deformation process was analyzed in detail, and five texture components were observed, including {001} $$\left\langle { 100} \right\rangle$$ , {011} $$\left\langle { 100} \right\rangle$$ , {112} $$\left\langle { 1 10} \right\rangle$$ , {111} $$\left\langle { 1 10} \right\rangle$$ , and {111} $$\left\langle { 1 1 2} \right\rangle$$ . As the true strain increased, deformation textures were gradually weakened due to an increase in the volume fraction of DRX grains. When the true strain was 0.8, the main texture components consisted of the recrystallization texture components of the {001} $$\left\langle { 100} \right\rangle$$ and {011} $$\left\langle { 100} \right\rangle$$ textures.

H13-mod steel developed after optimizing the composition and heat treatment process exhibits good hardness and impact toughness and can be used as a shield machine hob. Based on the Avrami equation, the dynamic recrystallization (DRX) behaviour of H13-mod steel during hot compression was studied in the temperature of 900–1150 °C and strain rate ranges of 0.01–10 s−1. A DRX model and finite element software were used to study DRX behaviour of H13-mod steel. Significant DRX was found at both low and high strain rates. Electron backscatter diffraction and optical microscopy analyses found different DRX nucleation mechanisms at low and high strain rates under different deformations. At a low strain rate, the nucleation was dominated by the strain-induced grain boundary migration, whereas the subgrain coalescence mechanism was dominant at a high strain rate. Moreover, dynamic recovery occurred in both processes. In addition, it was easier to obtain small and uniform equiaxed grains at high strain rates than at low strain rates.

The effect of hot working parameters on the microstructure and texture evolution of the hot-deformed Zr-45Ti-5Al-3V alloy was studied by the electron backscatter diffraction (EBSD) technique. It was found that a high density of dislocations were generated when the alloy was deformed at 700 °C/0.001 s−1 and 800 °C/1 s−1. With the increment in hot-deformation temperature and the decrease in strain rate, the dislocation density decreased due to the increase in dynamic recrystallization (DRX) degree. The discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) mechanisms co-existed during the hot working of the Zr-45Ti-5Al-3V alloy at a true strain of 0.7. The texture evolution of the alloy during hot working was characterized and the texture component mainly consisted of {001}, {011}, {110}, and {112} textures. The volume fractions of {001} and {011} textures obviously rose with the reduction in strain rate, whereas those of {110} and {112} textures gradually decreased. At a given strain rate, an increase trend in the volume fraction of the {001} texture was observed with rising hot-deformation temperature, while the volume fraction of the {011} texture first increased and then decreased. An opposite trend was visible in the {112} and {110} texture compared with {011} textures.

The effect of microstructure and microtexture on the mechanical properties of small-strain (e

A new type of low melting point Al-Si-Cu (Ni) filler metal for brazed 6063 aluminum alloy was designed, and the microstructure and properties of the filler metal were systematically studied. The results show that when the content of Cu in the Al-Si-Cu filler metal increased from 10 wt.% to 20 wt.%, the liquidus temperature of the filler metal decreased from 587.8 °C to 533.4 °C. Its microstructures were mainly composed of the α-Al phase, a primary Si phase, and a θ(Al2Cu) phase. After a proper amount of Ni was added to the Al-Si-20Cu filler metal, its melting range was narrowed, the spreading wettability was improved, and the microstructure was refined. Its microstructure mainly includes α-Al solid solution, Si particles, and θ(Al2Cu) and δ(Al3Ni2) intermetallic compounds. The results of the shear strength test indicate that the shear strength of the brazed joint with Al-6.5Si-20Cu-2.0Ni filler metal was 150.4 MPa, which was 28.32% higher than that of the brazed joint with Al-6.5Si-20Cu filler metal.

Mg–2Y–0.6Nd–0.6Zr alloy was first deformed by equal channel angular pressing (ECAP), then rolled and deformed under ultralow temperature conditions (liquid nitrogen immersion), and finally annealed. Optical microscopy (OM), electron backscatter diffraction technology (EBSD), and transmission electron microscopy (TEM) were used to analyze the evolution of the multiscale microstructure and changes in the mechanical properties of the alloy under ultralow temperatures and various annealing conditions. The results showed that the alloy treated with ECAP obtained fine grains, and a large number of fine twins were formed during the ultralow-temperature rolling process, which promoted the improvement of its hardness and strength and provided numerous preferential nucleation sites. The annealing made it easier to induce recrystallization and improve the recrystallization nucleation rate. The twin boundary produced by the alloy after ultralow-temperature rolling and the uniform fine grains formed by annealing resulted in excellent strength and plasticity of the alloy. The twins formed after rolling under ultralow temperatures were mainly {1 0 1 2} &lt, 1011&gt, tensile twins. The alloy had comprehensive mechanical properties with a tensile strength of 186.15 MPa and an elongation of 29% after annealing at 350 °C for 10 min.

In this work, the effect of double-ageing heat treatments on the microstructural evolution and mechanical behaviour of a metastable &beta, titanium Ti-3.5Al-5Mo-4V alloy is investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The double-ageing treatments are composed of low-temperature pre-ageing and high-temperature ageing, where the low-temperature pre-ageing is conducted at 300 &deg, C or 350 &deg, C for different times, and the high-temperature ageing is conducted at 500 &deg, C for 8 h. The results show that the phase transformation sequence is altered with the time spent during the first ageing stage, the isothermal &omega, phase is precipitated in the pre-ageing process of the alloy at 300 &deg, C and 350 &deg, C with the change in the ageing time, and the &omega, phase is finally transformed into the &alpha, phase with the extension of pre-ageing time. The existence time of the &omega, phase is shortened as the pre-ageing temperature increases. The microhardness of the alloy increases with increasing pre-ageing time and temperature. Compared with single-stage ageing, the &omega, phase formed in the pre-ageing stage changes the response to subsequent high-temperature ageing. After the two-stage ageing treatment, the precipitation size of the &alpha, phase is obviously refined after the double-ageing treatment. A microhardness test shows that the microhardness of the two-stage aged alloy increases with extended pre-ageing time.

The nucleation mechanism of ω-assisted α phase and the selection of α variants during isothermal aging of Ti-15Mo alloy were studied. The results show that α phase preferentially nucleates at the ω/β interface. The β→ω→α phase transition is affected by the long-range diffusion of solute atoms, involving lattice reconstruction and Mo diffusion. Due to the adaptive regulation of α variant, (0001)α1,2,3 and ( 01 1 0 )α1,2,3 variant were observed in the sample aged at 450 °C for 180 h. The orientation relationship between β matrix and α variants is as follows: β∥ 2 1 1 0 >α, {110}β∥{0001}α.

The effect of strain rate and deformation temperature on the α→β phase transformation in 47Zr-45Ti-5Al-3V alloy with an initial widmanstatten α structure was investigated. At the deformation temperature of 550 °C, the volume fraction of α phase decreased with increasing strain rate. At 600 and 650 °C, the volume fraction of α phase firstly increased to a maximum value with increasing strain rate from 1×10−3 to 1×10−2 s−1, and then decreased. At 700 °C, the microstructure consisted of single β phase. At a given strain rate, the volume fraction of α phase decreased with increasing deformation temperature. With decreasing strain rate and increasing deformation temperature, the volume fraction and size of globular α phase increased. At 650 °C and 1×10−3 s−1, the lamellar α phase was fully globularized. The variation in the volume fraction and morphology of α phase with strain rate and deformation temperature significantly affected the hardness of 47Zr-45Ti-5Al-3V alloy.

The effect of β grain size on stress-induced martensitic transformation in β solution-treated 51.1Zr-40.2Ti-4.5Al-4.2V alloy was investigated by using XRD and TEM techniques. The results show that initial β grain size has a profound effect on the triggering stress of the stress-induced martensitic (SIM) transformation. The triggering stress increases with increasing initial β grain size. The SIM transformation significantly affects the deformation behavior of the alloy. A typical double yielding is observed in the stress-strain curves due to the occurrence of the SIM transformation. The curve of work hardening rate vs. true strain is divided into three stages for the samples with small β grain size. The work hardening rate at stage ΙΙ or ΙΙΙ decreases with increasing initial β grain size, which is attributed to the effect of the SIM transformation during a tensile test.

The anisotropic fracture behavior of cold-drawn pearlitic steels was analyzed up to a true strain of 1.6. The structures were analyzed and quantified by scanning electron microscopy, electron backscatter diffraction and high-resolution electron microscopy. The aspect ratio Λ was defined to describe the fracture mechanism based on statistics pertaining to major axis and minor axis of pearlitic colonies, and the fitting formula was established as follows: Λ = 0.4 exp ( 2 x ) + 0.65 . At Λ ≤ 2.75, the fracture mechanism shifts from cleavage to quasi-cleavage fracture due to dislocation generation, as the measured parameters of interlamellar spacing (ILS) showed no obvious decrease. At values of Λ > 2.75, ductile fracture mechanism becomes dominant due to a drastic decrease in ILS. The ferrite fiber microtexture formed during the cold drawing process and the component exhibiting a gradient distribution from the surface to the central regions increased gradually with drawing. The crack propagation path was then deflected and formed a ‘V’ shape at e ≤ 1.5. However, as carbon migrated from cementite to the ferrite near the interphase, the fracture path deflected again. Furthermore, two reasonable models were formulated to explain fracture crack forming and anisotropic fracture behavior. In addition, this study illustrated that the relative crystallographic orientation of the ferrite and cementite components followed the Bagarytski relationship. With increasing strain, the cementite layers transformed from single crystals into nanostructured polycrystals and even evolved an amorphous structure at the interface at strains above 1.5.

The chloride induced corrosion behavior of cold drawn pearlitic steel wires was systematically investigated using electrochemical measurements, namely, electrochemical impedance spectroscopy, and local electrochemical impedance spectroscopy for micro-areas. A 0.05 mol/L NaCl solution mixed with borate buffer solution (pH = 8.45) was used. The results suggest that the corrosion resistance of cold-drawn pearlitic steel decreases with increasing strain to 0.8, but increases with strain up to a value of 1.6. Microstructure evolution was characterized by electron back scatter diffraction in combination with scanning electron microscopy and transmission electron microscopy. Atom probe tomography was used to quantify the cementite decomposition. The quantitation of microstructural parameters with strain suggests that the evolution of defect structure markedly increases the corrosion susceptibility of pearlite for strain up to 0.8. In the case of strain 1.6, refinement of the lamellar structure and cementite decomposition can reduce the volume fraction of cementite that acts as the cathode per corrosion unit (a pearlite/cementite “cell”), giving rise to an increase in the corrosion resistance.

The deformation and fracture behaviors of cementite in pearlitic steels during tensile tests were investigated by in situ scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and electron backscatter diffraction (EBSD). The results showed that the deformed structure had three different types of shear bands: shear deformation in the pearlite colonies, at the interfaces of the pearlite colonies and at the phase boundary between ferrite and cementite. The orientations of the shear bands were nearly anisotropic with respect to the tensile axis. The path of shear deformation developed at the dislocation walls and was propagated by the offset of the cementite along the dislocation walls. As the dislocations cut perpendicularly through the cementite layers, the single-crystalline cementite platelets were divided into many nanometer-sized subgrains by the effects of the shearing stress. This process hindered dislocation movement and led to the accumulation of complex dislocations at the adjacent ferrite lamellae. Thus, the plastic deformation of the cementite layers was characterized by bulging until they fractured. The pearlitic texture component was evenly distributed, and the crystallographic axes of the colonies were randomly oriented. Hence, three different shear models characterized the crack propagation process, which occurred in a linear fashion and could be considered the pearlite colonies as a displacement unit for forward expansion.

The 47Zr-45Ti-5Al-3V (wt.%) alloy was solution-treated at 850 and 780 °C for 30 min and then rolled at different temperatures. The effect of rolling temperature on microstructure and tensile properties was investigated. The results showed that the microstructure contained a large amount of α phase at a rolling temperature of 600 °C. As the rolling temperature increased, the amount of α phase decreased, whereas the amount of β phase increased. When the rolling temperature was higher than 700 °C, the alloy was composed of a single β phase. The tensile properties of the alloy depended strongly on rolling temperature. The yield strength and tensile strength decreased with increasing rolling temperature, whereas the elongation increased. At a given rolling temperature, low solution treatment temperature resulted in higher strength and lower elongation than high solution treatment temperature. The fracture mode changed from cleavage fracture and quasi-cleavage fracture to dimple fracture with increasing rolling temperature.

The effects of microstructure, texture evolution and strengthening mechanisms on mechanical properties of 3003 aluminum alloy during cryogenic rolling (CR) and room temperature rolling (RTR) processing were investigated by electron backscatter diffraction, transmission electron microscopy and X-ray diffraction. The results show that the CR processing can significantly decrease the size of sub-grains and second-phase particles, and increase the dislocation density of the 3003 aluminum alloy. During the CR and RTR processing, the initial Cube and R-Cube textures are gradually rotated into the β-fiber texture. The CR processing can obviously delay the texture evolution from initial Cube texture to β-fiber texture during rolling. A significant enhancement in the yield strength, ultimate tensile strength and elongation of the 3003 aluminum alloy after the CR processing is obtained comparing with the RTR processing. This can be explained by the contribution of dislocation strengthening and grain refinement strengthening.

Co-based superalloy GH159 and Ni-based superalloy GH4169 have been successfully joined by laser beam welding and the effect of heat input on microstructure and properties of dissimilar joints were investigated systematically. The results showed that weld seams exhibited a nail shape and full penetration was attained at all dissimilar joints. Increasing grain size towards the fusion zone (FZ) were observed in the heat affected zone (HAZ) on the GH159 side while an increasing dissolution of γ′ and γ′ towards the FZ was attained at the HAZ on the GH4169 side. These resulted in decreasing microhardness towards FZ. Tensile failure was found in the FZ with the lowest microhardness. Meanwhile, the ultimate tensile strength (UTS) of the dissimilar joints increased with the decreasing of heat input. The high UTS of dissimilar joint with low heat input can be ascribed to the lower volume fraction of the Laves phase and the smaller dendrite arm spacing.

The relationship between microstructure parameters and mechanical properties was studied in this paper. The steel was heat-treated at different austenitizing temperatures to acquire varying microstructure. The results showed that austenite grain size increases with austenitizing temperature, while the pearlite colony size was relatively constant. The strength followed a Hall&ndash, Petch relationship with the austenite grain size, but the austenite grain size has nothing to do with the impact toughness. The control unit for determining the impact toughness of pearlitic steel is the pearlite colony size using a comparison method. Further studies have found that, in the hypoeutectoid steel and hypereutectoid steel, the pearlite colony size changes with the austenitizing temperature. However, when the eutectoid steel with a carbon content of 0.81% undergoes the isothermal transformation, the number of grain boundary precipitates is very few. There are many nucleation sites at the grain boundary. The pearlite colonies randomly nucleate at the grain boundaries and grow into the interior of the grains. Simultaneously, new pearlite colonies nucleate by the side of the existing pearlite colony. The intragranular pearlite colonies are also randomly nucleated. These nucleation sites increase the chance of the growing pearlite colonies colliding with each other, eventually resulting in a constant pearlite colony size.

The high-temperature flow behavior of TB8 titanium alloys with two different grain sizes was investigated in this present work. Results show that a significant characteristic of stress drop is visible at the start stage of the hot deformation process when the strain rates are 100 and 10&minus, 1 s&minus, 1. With the further increasing of strain, the flow stress initially rises to a maximum value and subsequently attains a plateau for the strain rates of 100 s&minus, 1 and a slight decrease for the strain rates of 10&minus, 1. Only dynamic recovery occurs under these deformation conditions. When the strain rates drop to 10&minus, 3 s&minus, 1, the dynamic recrystallization takes place during hot deformation. The values of deformation activation energy and materials constants at different strains were calculated. The processing maps at different strains were established for the fine- and coarse-grained alloys. The optimal processing parameter for hot processing was attained to be 900 &deg, C/10&minus, 1 for fine-grained alloys and 950 &deg, 1 for coarse-grained alloys, respectively.

The effect of microstructure on the mechanical properties of Ti-20Zr-6.5Al-4V alloy after solution and aging treatment was investigated by compression tests. The results showed that the microstructure was consisted of a duplex phase αʺ + β structure after solution treatment. With increasing solution treatment temperature, the size of β phase grain increased and the amount of αʺ phase decreased. The ultimate compressive strength and elongation decreased with increasing solution treatment temperature, while the yield strength increased. After aging-treatment at 700 ºC for 1.5 h, the microstructure consisted of a large amount of globular α phase, a little amount of fine acicular α phase and bulk β phase for the samples solution-treated at 850 ºC for 0.5 h. With increasing initial solution treatment temperature, the amount of globular α phase and bulk β phase decreased, however, the amount and size of acicular α phase increased after aging treatment. The ultimate compressive strength and elongation decreased with increasing initial solution treatment temperature, whereas the yield strength firstly increased, and then slightly decreased.

High-strength, multiphase steels consisting of pearlite surrounded by tempered martensite were prepared by pre-quenching and ultrafast tempering heat treatment of high-carbon pearlitic steels (0.81% C). The microstructures were analyzed by scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. With an increasing quenching temperature from 120 &deg, C to 190 &deg, C, the quenched martensite variants nucleated via autocatalytic nucleation along the interface. Furthermore, the tempered nodules exhibited a distinct symmetrical structure, and the tempered martensite and pearlitic colonies in the group also showed a symmetrical morphology. In addition, a reasonable model was formulated to explain the transformation process from quenching martensite to the multiphase microstructure. When the quenching temperature was set to 120 &deg, C, followed by ultrafast heating at 200 &deg, C/s to 600 &deg, C and subsequent isothermal treatment for 60 s, the multiphase structure showed highest strength, and the pearlite volume fraction after tempering was the lowest. The microhardness softening mechanism for the tempered structures consisted of two stages. The first stage is related to martensitic sheets undergoing reverse transformation and the nucleation of cementite on dislocations. The second stage involves the transformation of austenite into pearlite and continued carbide coarsening in the martensitic matrix.

The dynamic recrystallization (DRX) behavior of 47Zr-45Ti-5Al-3V alloy was studied by using the experiment and numerical simulation method based on DEFORM-3D software and cellular automata (CA) over a range of deformation temperatures (850 to 1050 °C) and strain rates (10−3 to 100 s−1). The results reveal that the DRX behavior of 47Zr-45Ti-5Al-3V alloy strongly depends on hot-working parameters. With rising deformation temperature (T) and decreasing strain rate (ε˙), the grain size (dDRX) and volume fraction (XDRX) of DRX dramatically boost. The kinetics models of the dDRX and XDRX of DRX grains were established. According to the developed kinetics models for DRX of 47Zr-45Ti-5Al-3V alloy, the distributions of the dDRX and XDRX for DRX grains were predicted by DEFORM-3D. DRX microstructure evolution is simulated by CA. The correlation of the kinetics model is verified by comparing the dDRX and XDRX between the experimental and finite element simulation (FEM) results. The nucleation and growth of dynamic recrystallization grains in 47Zr-45Ti-5Al-3V alloy during hot-working can be simulated accurately by CA simulation, comparing with FEM.

The dynamic recrystallization (DRX) behavior in the hot working of TB8 titanium alloy was studied by using the experiment and finite element simulation (FEM) method. The results showed that the DRX behavior of TB8 titanium alloys was drastically affected by the hot processing parameters. The rising deformation temperature and reducing strain rate led to an augmentation in the grain size (dDRX) and volume fraction (XDRX) of DRX grains. In view of the true stress&ndash, strain curves gained from the experiment, the dDRX and XDRX models of DRX grains were constructed. Based on the developed models for DRX of TB8 titanium alloy, the isothermal forging process of the cylindrical samples was simulated by the DEFORM-3D software. The distributions of the effective strain and XDRX for DRX were analyzed. A comparison of the dDRX and XDRX of DRX grains in the central regions of the samples between the experimental and FEM results was performed. A good correlation between the experimental and simulation results was obtained, indicating that the established FEM model presented good prediction capabilities.

The &beta, &rarr, &alpha, phase transition kinetics of the Ti&ndash, 3.5Al&ndash, 5Mo&ndash, 4V alloy with two different grain sizes was investigated at the isothermal temperature of 500 &deg, C. A method to estimate the function of the precipitate fraction of the &alpha, phase with different aging times was developed based on X-ray diffraction analysis. The value of the &alpha, precipitate fraction increased sharply at first, then increased slowly with the aging time, and finally reached equilibrium. The value of the &alpha, precipitate fraction was higher in the alloy aged for the same time at a higher solution temperature, while the size of the &alpha, precipitate was smaller at a higher solution temperature. The &beta, phase transition kinetics under isothermal conditions were modeled in the theoretical frame of the Johnson&ndash, Mehl&ndash, Avrami&ndash, Kolmogorov (JMAK) theory. The kinetic parameters of JMAK deduced different transformation mechanisms. The mechanism of the phase transition in the first stage was dominated by mixed transformation mechanisms (homogeneously nucleated and acicular-grown &alpha, structure, and grain boundary-nucleated and grown &alpha, precipitate), while the second stage was the growth of the fine &alpha, precipitate, which was controlled by slow diffusion. As the aging time increased, the hardness of the Ti&ndash, 4V alloy increased sharply. After the hardness of the alloy reached a plateau, it began to decline. The hardness of the alloy was always higher at a higher solution temperature.

The H13-mod steel optimized by composition and heat treatment has reached the performance index of the shield machine hob. The hot deformation behavior of the H13-mod steel was investigated by compression tests in the temperature range from 900 to 1150 &deg, C and the strain rate range from 0.01 to 10 s&minus, 1. The true stress-strain curve showed that the rising stress at the beginning of deformation was mainly caused by work hardening. After the peak stress was attained, the curve drop and the flow softening phenomenon became more obvious at low strain rates. The flow behavior of the H13-mod steel was predicted by a strain-compensated Arrhenius-type constitutive equation. The relationship between the material constant in the Arrhenius-type constitutive equation and the true strain was established by a sixth-order polynomial. The correlation coefficient between the experimental value and the predicted value reached 0.987, which indicated that the constitutive equation can accurately estimate the flow stress during the deformation process. A good linear correlation was achieved between the peak stress (strain), critical stress (strain) and the Zener‒Hollomon parameters. The processing maps of the H13-mod steel under different strains were established. The instability region was mainly concentrated in the high-strain-rate region, however, the microstructure did not show any evidence of instability at high temperatures and high strain rates. Combined with the microstructure and electron backscattered diffraction (EBSD) test results under different deformations, the optimum hot working parameters were concluded to be 998&ndash, 1026 &deg, C and 0.01&ndash, 0.02 s&minus, 1 and 1140&ndash, 1150 &deg, 0.057 s&minus, 1.

This paper aims to reveal how multi-level lamellar microstructure influences strength and toughness of TC21 alloy after different solution treatment ranging from 980 °C to 1020 °C and annealed at 770 °C. Microstructural characterization was performed by using optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscope (TEM), and image analysis software. Results show that the size of β grains (dβ) grows significantly while α colony (dc) increases slowly with the solution temperature increases. Meanwhile, α plate (dα) presents an opposite tendency. In addition, the Hall-Petch formula was applied to reveal the relationship between multi-level microstructure (including prior β grain, α colony and α plate) and strength and toughness of the alloy; α colony could be a key microstructure unit correlated to strength of the alloy. Besides, α plate obeys the Hall-Petch relationship with toughness. Meanwhile, it is confirmed by EBSD that more α plate were cut with the increasing size of the multi-level lamellar microstructure. The larger α colony size is, the stronger the interaction between the crack and α plate. Thus, α plate was regarded as the key microstructure unit for influencing toughness because it strongly hinders the crack initiation and growth. Keywords: TC21 alloy, Multi-level microstructure, Correlated microstructure unit, Strength, Toughness