Measurement of the Anisotropic Dynamic Elastic Constants of Additive Manufactured and Wrought Ti6Al4V Alloys

Additively manufactured (AM) materials and hot rolled materials are typically orthotropic, and exhibit anisotropic elastic properties. This paper elucidates the anisotropic elastic properties (Young’s modulus, shear modulus, and Poisson’s ratio) of Ti6Al4V alloy in four different conditions: three AM (by selective laser melting, SLM, electron beam melting, EBM, and directed energy deposition, DED, processes) and one wrought alloy (for comparison). A specially designed polygon sample allowed measurement of 12 sound wave velocities (SWVs), employing the dynamic pulse-echo ultrasonic technique. In conjunction with the measured density values, these SWVs enabled deriving of the tensor of elastic constants (Cij) and the three-dimensional (3D) Young’s moduli maps. Electron backscatter diffraction (EBSD) and micro-computed tomography (μCT) were employed to characterize the grain size and orientation as well as porosity and other defects which could explain the difference in the measured elastic constants of the four materials. All three types of AM materials showed only minor anisotropy. The wrought (hot rolled) alloy exhibited the highest density, virtually pore-free μCT images, and the highest ultrasonic anisotropy and polarity behavior. EBSD analysis revealed that a thin β-phase layer that formed along the elongated grain boundaries caused the ultrasonic polarity behavior. The finding that the elastic properties depend on the manufacturing process and on the angle relative to either the rolling direction or the AM build direction should be taken into account in the design of products. The data reported herein is valuable for materials selection and finite element analyses in mechanical design. The pulse-echo measurement procedure employed in this study may be further adapted and used for quality control of AM materials and parts.

Tensile Deformation and Fracture Behavior of API-5L X70 Line Pipe Steel

Thermo-mechanical controlled processing (TMCP) is employed to obtain the required level of mechanical properties of contemporary HSLA steel plates utilized for gas and oil pipeline production. The strength and crack resistance of pipeline steels are mainly determined by its microstructure and crystallographic texture. In this study, the influence of the structural and textural states of industrially produced API-5L X70-X80 pipeline steels on tensile mechanical properties was analyzed. TMCP routes with different hot rolling temperatures and cooling rates were employed. The texture of steel was assessed using the Taylor factor, which was calculated based on electron backscatter diffraction (EBSD). The decrease in rolling temperature resulted in the sharper texture characterized by {001} planes banding (cleavage planes in the bcc lattice) parallel to rolling direction. The tensile deformation behavior at the stage of necking was determined by the crystallographic and morphological texture of the material and demonstrated significant anisotropy. Rupture of all investigated samples was accompanied by the development of splitting on the fracture surface. The splitting was localized in the rolling plane similar to the splitting in standard Charpy tests of pipeline steels.

Study of the anisotropy of carbon steel sheet by the tensile test

In test laboratories, the characteristics of the sheets shall be determined by the tensile test on specimens taken in the direction perpendicular to the rolling direction, and these characteristics shall be used as the date of entry into the process of calculating the parts made of the sheet. In the case of parts with special characteristics such as safety parts in the automotive industry, or for mechanically stressed parts in a certain direction, it is important to know precisely the values of the mechanical characteristics of the sheet in relation to the rolling direction, so as to ensure the required resistance. Also, in the case of stamped parts, their quality is all the better the lower the anisotropy. The paper presents the results of experimental research on the mechanical characteristics of the sheet DC04 with a thickness of 0,65 mm, determined by tensile testing on sets of 7 test specimens, taken every 15 degrees from the rolling direction.

Influence of Longitudinal Scratch Defects on the Bendability of Titanium Alloy

Post-manufacturing induced defects in the form of scratches are sometimes inadvertently introduced onto sheet metal surfaces during either transportation, storage or handling. However, limited research has been previously carried out to establish the impact of such surface defects on sheet formability. Test trial results after press brake forming of Ti-3Al-2.5V showed that for longitudinal scratches oriented along the sheet rolling direction, scratch profiles with depth in the ranges of -1μm to -18μm and pile up height between 1μm to 16μm can be successfully formed; hence could be deemed acceptable during the sheet selection process. Failure of the coupons during the press brake forming trials was due to the impact of the scratch defects in their role as stress raisers and occurred primarily at the longitudinal scratch defect zones

Effect of low temperature rolling on mechanical properties and corrosion resistance of CrCoNi medium entropy alloy

Abstract: For the casted CrCoNi medium entropy alloy melted by magnetic levitation, the deformation was carried out in 4 passes under the condition of liquid nitrogen temperature (-196°C), the total reduction was 50%,The microstructure and properties were analyzed after liquid nitrogen low temperature rolled. The experimental data showed that the phase structure of the alloy was not changed under the low-temperature rolling. The grains, crushed and refined, were elongated along the rolling direction. With the increasing of passes and reduction, the tensile strength increased from 585 MPa to 1359 MPa, while the elongation decreased from 37.8% to 5.9%. work With the increasing of work hardening,the tensile strength of the CrCoNi medium entropy alloy gradually increased, while the plasticity dramatic decreased. At the same time,the corrosion resistance of the CrCoNi medium entropy alloy was improved by low temperature cold rolled. The corrosion resistance of as-cast and rolled CrCoNi was much better than 304 stainless steel.

Textures of Non-Oriented Electrical Steel Sheets Produced by Skew Cold Rolling and Annealing

In order to investigate the effect of cold rolling deformation mode and initial texture on the final textures of non-oriented electrical steels, a special rolling technique, i.e., skew rolling, was utilized to cold reduce steels. This not only altered initial textures but also changed the rolling deformation mode from plane-strain compression (2D) to a more complicated 3D mode consisting of thickness reduction, strip elongation, strip width spread and bending. This 3D deformation induced significantly different cold-rolling textures from those observed with conventional rolling, especially for steels containing low (0.88 wt%) and medium (1.83 wt%) amounts of silicon at high skew angles (30° and 45°). The difference in cold-rolling texture was attributed to the change of initial texture and the high shear strain resulting from skew rolling. After annealing, significantly different recrystallization textures also formed, which did not show continuous <110>//RD (rolling direction) and <111>//ND (normal direction) fibers as commonly observed in conventionally rolled and annealed steels. At some skew angles (e.g., 15–30°), the desired <001>//ND texture was largely enhanced, while at other angles (e.g., 45°), this fiber was essentially unchanged. The formation mechanisms of the cold rolling and recrystallization textures were qualitatively discussed.

Effect of the Initial Texture, Recrystallization and Re-Dissolution Process on the Evolution of Texture during Solution Treatment of the 7A65 Hot Rolled Plate

The evolution of textures, the degree of recrystallization and the mechanical properties of 7A65 hot rolled plates during re-dissolution were studied with different thicknesses (25 mm, 65 mm, 120 mm) and different degrees of deformation. It was found that different plates exhibited different trends of re-dissolution because the degrees of deformation increased and the degrees of recrystallization were different during the solution treatment. With the increase of deformation and static recrystallization degrees, texture types changed from Cube, R-Cube to Brass, R, Cube and Copper during the re-dissolution process. The value of the Schmid factor (µ(-)) was calculated and the value along the rolling direction was significantly larger than along the transverse direction, which led to a lower yield strength along the rolling direction. In terms of the average contribution of the yield strength, the strengthening of the grain boundary including LAGBs (low-angle grain boundaries) was found to play a more significant role than the effect of solid atoms and dislocation densities. Therefore, the 25 mm plate exhibits the best mechanical properties, with a yield strength of 565.7 MPa along the rolling direction.

Pitting Corrosion Behavior and Surface Microstructure of Copper Strips When Rolled with Oil-in-Water Emulsions

Copper strips experience severe corrosion when rolled with an oil-in-water (O/W) emulsions lubricant. The effects of rolling reduction on the pitting corrosion behavior and surface microstructure of Cu strips were studied in detail using electrochemical measurements and electron back scattered diffraction (EBSD) analysis. It was found that the corrosion current densities of the rolled Cu strips increased with accumulated reduction, which also lowered the pitting potentials and weakened their corrosion resistances. Therefore, the corrosive tendency of Cu strips under different rolling reductions (ε) followed the order of ε0% < ε20.7% < ε50.6% < ε77.3%. The Cu surface easily reacted with chlorine, sulfur, and carbon components from O/W emulsions to generate pitting corrosion. Under the interactive effect of pitting corrosion and stress corrosion, pits expanded along the rolling direction. The aggregation of anions in surface defects, such as dislocations, metastable pits, and microcracks, further accelerated the pitting corrosion of the surface.

Effect of Rolling Orientation on the Microstructure and Mechanical Properties of AZ31B Mg Alloy

The magnesium AZ31B alloy has been utilized in a variety of applications within the automotive and aviation industries due to its high specific strength, low-cost processing, and low density. However, the AZ31B alloy generally has poor ductility and limited workability at room temperature. The objective of this study was to develop a manufacturing processing technique to increase the potential uses of this alloy. The methodology includes cold rolling and annealing using small pass reductions until the samples reached a final thickness of 1.78 mm (0.07 in). The samples were cut into 10.16 mm (0.4 in), 7.62 mm (0.3 in), and 5.08 mm (0.2 in) thicknesses prior to cold rolling and were rolled in 0-, 45-, and 90-degree rolling directions. The grain shapes and sizes were examined via optical microscopy. Tensile testing was conducted to determine the strength and ductility. Scanning electron microscopy (SEM) images were taken to evaluate fractured surfaces. All processes including rolling direction and furnace cooling or air cooling after annealing produced similar results of medium strength (245-250 MPa in ultimate strength, 122-127 MPa in yield) and greater than 22.5% elongations in very thin sheets. Samples rolled along the 45-degree direction produced the highest percent reduction in thickness.