Two-step Cold Research Articles

La drives the remarkable strength enhancement of the Cu-Cr-Zr alloy through traditional thermo-mechanical treatment

The Cu-1Cr-0.1Zr alloy with different La addition (0 %, 0.07 % and 0.14 wt%) was processed using industry suitable two-step cold rolling and aging treatment to achieve superior strength and electrical conductivity. The role of La addition on the microstructure evolution and comprehensive properties of the Cu-1Cr-0.1Zr alloy is investigated during the second rolling and subsequent aging stages. During pre-aging process, the presence of La in the Cu-1Cr-0.1Zr-0.07La alloy led to formation of smaller precipitate sizes compared to La-free Cu-1Cr-0.1Zr alloy. This facilitates a stronger cut interaction between dislocations and precipitates during secondary rolling process, which promotes the redissolution of precipitates into Cu matrix and thus results in a larger decline of 44.72 % ICAS for the electrical conductivity of Cu-1Cr-0.1Zr-0.07La alloy. After post-aging treatment, precipitates are newly formed with increased number and refined size of Cr precipitates with maintaining a coherent relationship with the matrix. Besides, the addition of La promotes Cr-rich phase precipitation and dislocation accumulation. Resultantly, remarkable increase in tensile strength by 11 % with the addition of 0.07wt%La. While, the 0.14La added alloy exhibits comprehensive properties of tensile strength 600 MPa and electrical conductivity 80.08 %IACS after aging at 440 °C for 180 min. The increase in strength was primarily attributed to precipitation strengthening and dislocation strengthening. This work provides new kinds of Cu-1Cr-0.1Zr alloy and industrial suitable thermo-mechanical treatment for fabricating high performance cooper alloy sheets.

Creep Analysis and Material Properties Research of Rotary Calciner

Unavoidably, during the aqueous reprocessing of spent fuel, high level liquid waste is produced, which is typically vitrified. A rotary calciner is an essential component of a two-step cold crucible melter equipment system. Owing to the calciner’s long-term operation under high temperature condition, potential effects from metal creep are essential design factors. Stable temperature and stress fields of components of a rotary calciner have been calculated based on the finite element analysis software ANSYS. Furthermore, creep life of creep effects has been evaluated and comparisons among Inconel 690, Inconel625, and SUS 310s tubes’ mechanical property performance have been conducted. The results indicate that all three materials require the mechanical property requirements and SUS 310s exhibits the minimum creep displacement.

Two-step cold sintering of Li1.3Al0.3Ti1.7(PO4)3 composite solid electrolyte with non-equilibrium microstructures for enhanced electrochemical performance

High densification and high electrochemical performance were obtained in solid-state electrolytes with non-equilibrium microstructures by two-step cold sintering.

Cold sintering of BaZr0.8Y0.2O3-ẟ ceramics: Phase formation and grain boundary properties

Electrochemical devices based on the proton conducting ceramic BaZrO3 have shown their immense potential for efficient energy conversion and gas separation processes at intermediate temperatures. A major drawback of this material class is the inevitably high sintering temperature, which is necessary to reach sufficient densities for gas tightness. Recently, cold sintering has been applied to densify BaZrO3 – BaCeO3 solid solutions at low temperatures using a partial dissolution of the Ce-rich phase. Here, we apply the method to BaZr0.8Y0.2O3-ẟ (BZY20), which is a Ce-free proton conducting ceramic. We show that densification by cold sintering is viable at temperatures between 150 °C and 250 °C under uniaxial pressures of 400 MPa and deionized water as a sintering aid. The dissolution of yttrium from BZY20 during cold sintering acts as the trigger for densification at low temperatures but forms Y(OH)3 as an instable side product. Therefore, we developed a two-step cold sintering process that adds an additional thermal treatment between 900 and 1100 °C directly after the cold sintering process to enable electrochemical characterization and transmission electron microscopy investigations.

A novel two-step cold sintering process to fabricate dense ZnO nanocrystalline ceramics

The cold sintering process, a novel technique for low-temperature ceramic processing, effectively removes interparticle pores via dissolution and re-precipitation. However, it often triggers grain growth, especially in nanocrystalline ceramics. To address this issue, the present study proposed an innovative two-step cold sintering process with an initial step at 1.5 GPa/RT (room temperature) for 10 min, followed by a subsequent step at 300 MPa/250 °C for 45 min. This method yields ZnO nanocrystalline ceramics with 97.5 % relative density and a 39 nm average grain size (from 30 nm powder). The initial high-pressure step significantly enhances the pressure gradient and particle solubility, leading to very high supersaturation and the occurrence of homogenous nucleation during pressure release. Subsequently, the formation of the crystal nuclei in the interparticle voids can dramatically improve the density of the compact by the additional pore filling and avoid recrystallization-induced grain growth during the second-step cold sintering process.

Submicron Sr0.7Bi0.2TiO3 dielectric ceramics for energy storage via a two-step method aided by cold sintering process

A serials of relaxor ferroelectrics of Sr0.7Bi0.2TiO3 ceramics with different grain sizes were prepared by a conventional sintering (CS) and a two-step cold sintering aided process (CSP) method. The microstructure, dielectric and energy storage performance of the synthesized ceramics were systematically studied. Owing to the involvement of CSP, grain size is reduced to submicrometer scale, and uniform and dense morphology are achieved at a lower sintering temperature compared with the CS method. As a consequence, high critical electric field (420 kV/cm), a good recoverable energy storage density (3.32 J/cm3), and a superior energy efficiency (92.84 %) can be realized for the ceramic via CSP sintered at 1170 °C. Meanwhile, it also exhibits good stability over wide ranges of measuring frequencies and temperatures, and increasing cycles to 107. A high power density (85.46 MW/cm3) is achieved due to a very fast discharge rate (∼61.7 ns). Moreover, the synthesized ceramic demonstrates an ultrahigh hardness of ∼ 8.73 GPa. These results indicate that CSP is a feasible solution to achieve outstanding comprehensive dielectric energy storage performance by utilizing the synergistic effects of grain refinement and densification.

Raw Milk for Provolone Valpadana PDO Cheese: Impact of Modified Cold Storage Conditions on the Composition of the Bacterial Biota

The raw milk for production of long-ripened, spicy type, Provolone Valpadana (PV) PDO cheese must be stored, refrigerated, and processed within 60 h from the first milking, according to European and Consortium regulations. Low-temperature storage conditions preserve the hygienic quality, but also reduce the diversity and content of dairy microbiota, which is important to define the characteristics and quality of raw milk cheeses. Eleven bulk, raw milk samples were stored, at laboratory level, under two different time/temperature conditions (i.e., 10 °C or 12 °C for 15 h, then cooled to 4 °C for 45 h). The count of different bacterial groups and the diversity of bacterial communities were determined before and after storage by culture-dependent and DNA metabarcoding methods, respectively. The two-step cold storage conditions increased the mesophilic, psychrotrophic, lipolytic, and proteolytic bacterial load, without affecting the hygienic quality of milk. Among the 66 dominant and 161 subdominant taxa retrieved by DNA metabarcoding, Acinetobacter, Pseudomonas, and the lactic acid bacteria belonging to the genera Lactococcus and Streptococcus were present in almost all the raw milk samples, and their relative abundance was positively related with the total bacterial count. The storage conditions tested could be considered for eventual application in long-ripened PV cheese production to rationalize storage, transfer, and processing of raw milk.

Effective grain size refinement of an Fe-24Ni-0.3C metastable austenitic steel by a modified two-step cold rolling and annealing process utilizing the deformation-induced martensitic transformation and its reverse transformation

Metastable austenitic steels having ultrafine grained (UFG) microstructures can be fabricated by conventional cold rolling and annealing processes by utilizing the deformation-induced martensitic transformation during cold rolling and its reverse transformation to austenite upon annealing. However, such processes are not applicable when the austenite has high mechanical stability against deformation-induced martensitic transformation, since there is no sufficient amount of martensite formed during cold rolling. In the present study, a two-step cold rolling and annealing process was applied to an Fe-24Ni-0.3C metastable austenitic steel having high mechanical stability. Prior to the cold rolling, a repetitive subzero treatment and reverse annealing treatment were applied. Such a treatment dramatically decreased the mechanical stability of the austenite and greatly accelerated the formation of deformation-induced martensite during the following cold rolling processes. As a result, the grain refinement was significantly promoted, and a fully recrystallized specimen with a mean austenite grain size of 0.5 μm was successfully fabricated, which exhibited both high strength and high ductility.

The preparation of high-density aluminum-doped zinc oxide ceramics by cold sintering process

Abstract High-density Aluminum-doped zinc oxide (AZO) ceramic was prepared via the densification process by ultralow-temperature Two-step Cold sintering processes (TS-CSP). Density, microstructure and electrical properties of the preparation AZO ceramics were investigated. The results show that Al-doping concentration has an important influence on the densification of AZO ceramics. When the doping amount of Al2O3 was 2.0 wt%, and an acetic acid solution was used as a co-solvent, a high-performance AZO ceramic was obtained. AZO ceramics has a uniform phase and containing no other impurities, with a relative density of up to 99.23%and a resistivity as low as 5.58 × 10−3 Ω cm. The AZO ceramic prepared by this method has a significant application prospect.

Tailoring the residual stress during two-step cold gas spraying and friction-stir surface integration of titanium coating

In this article, a novel processing route combining cold gas spraying (CGS) and friction-stir processing (FSP) was employed to fabricate a dense titanium surface coating with high integrity and superior mechanical property. After subsequent implementation of CGS and FSP processes, a coating layer with refined grain structure (<1 μm) and enhanced hardness (up to seven times higher) was deposited on the surface, and influenced the residual stress. The residual stress and its distribution largely depended on the plunge depth of FSP modification step, and became more compressive with a maximum negative value of around 400 MPa at the advancing side by increasing the depth of tool plunging and promotion of coating integration.

Investigation of microstructure and properties of strip-cast 4.5 wt% Si non-oriented electrical steel by different rolling processes

A 4.5 wt% Si as-cast strip with equiaxed grains microstructure fabricated by twin-roll caster was subjected to three different cold rolling and final recrystallization annealing processes. The results revealed that the rolling process has a significant effect on the evolution of microstructure and texture of the strip-cast 4.5 wt% Si non-oriented electrical steel. Moreover, both mechanical and magnetic properties of the steel exhibited various characteristics because of different rolling routes. After short-time annealing at high temperature, the steel sheet experienced one-step cold rolling exhibits the highest tensile strength. Regarding two-step cold rolling, better magnetic properties were obtained after a second cold rolling with a slight reduction. The excellent performance of mechanic and magnetic properties can be fabricated by two-step medium reduction cold rolling.

The effect of grain size and initial texture on microstructure, texture, and formability of Nb stabilized ferritic stainless steel manufactured by two-step cold rolling

The present study investigated the influence of grain size and initial texture on the microstructure, texture, and formability of a niobium-stabilized ferritic stainless steel processed by two-step cold rolling. The characterization of the samples was performed by X-ray diffraction, electron backscatter diffraction, and tensile tests in order to evaluate the formability by the average normal anisotropy coefficient. The results showed that the reduction in grain size from 110 ± 21 to 50 ± 7 μm, in the hot rolled band, was favorable to obtain a more homogenous microstructure and smaller grain size after annealing. Coarse grain size and α-fiber (<110>||RD) favored a strong α-fiber after cold rolling. In addition, γ-fiber (<111>||ND) was more intense in the deformation texture of fine grain size samples. The recrystallization texture was constituted by intense γ-fiber (<111>||ND) and weak θ-fiber (<100>||ND) for both conditions. However, the reduction in grain size increased the γ-fiber fraction. Therefore, the r¯=1.92 and γ/θ = 8.12 were obtained to the sample originated from the initial fine grain size. The fine grain size and weak texture in the starting materials were effective in developing a high r¯ value in the samples manufactured by two-step cold rolling.

Preparation of high density ZnO ceramics by the Cold Sintering Process

Abstract High-density ZnO ceramics were prepared by a Two-Step Cold Sintering Process (TS-CSP) at an ultralow-temperature. The densification process of ZnO ceramics was demonstrated by TS-CSP. And the density, microstructure and electrical properties of the ZnO ceramics were investigated. The results indicate that most of the crystallization of ZnO ceramic can be completed in the first step of sintered at 150 °C/200 MPa for 30 min, with a relative density approaching 97.36%. This relative density was further improved to 99.43% after the second sintering step was deployed at 200 °C/200 MPa for 30 min, which displayed an average grains size of 1.5 μm and resistivity of 0.125 Ω cm. This work demonstrated an effective method to reduce CSP temperature and pressure in the production of high-performance ZnO ceramics.

Mechanism of huge Lüders-type deformation in ultrafine grained austenitic stainless steel

A remarkable Lüders-type localized deformation having a huge Lüders strain of 0.4 was observed in tensile deformation of an ultra-fine grained austenitic stainless steel fabricated by two-step cold rolling and annealing processes. It was clarified that the Lüders-type deformation in the material was essentially the same as necking caused by plastic instability, but the enhanced strain hardening by deformation induced martensitic transformation realized the stable propagation of the strain localized band, leading to the huge Lüders strain as well as high strength and large ductility of the material.

Quality evaluation of rapeseed oils used as engine fuels

Samples from six reference decentralised facilities and one industrial production unit of rapeseed oils were taken for the evaluation of the influence of production processes to the properties specified in the technical standard; in the laboratories, the properties limited by the standard for rapeseed oils were determined. In addition, long-term monitoring of changes in the oxidation stability in the storage test of rapeseed oils additived in the quantities of 200, 400 and 600 mg.kg−1 of the Baynox antioxidant was started. The results confirmed that the critical points in the rapeseed oil production process consist in the contamination with ash-forming elements, such as phosphorus, magnesium, calcium and overall impurities. Not only in the case of hot pressing, but also in two-step cold pressing of rapeseed it is necessary to reduce the content of ash-forming elements using additional processes, such as degumming, neutralisation and whitening. The safety step consisting of filtration down to maximum particle size of 1 μm must be always in place before the oil distribution. A positive effect of the Baynox antioxidant was clearly proved. As 200 mg.kg−1 of Baynox was added, the oxidation stability value increased from 8 to 9.05 hrs immediately after the pressing with a consequent decrease to 6 hrs after 270 days. With using of addition 400 ppm Baynox decreased oxidation stability under 6 hours not until after 390 days of storage. With addition 600 ppm Baynox the oxidation stability of rapeseed oil even after 510 days of storage makes 6.5 hours. The quality monitoring brought about necessary findings and knowledge for the optimisation of the rapeseed oil production and distribution as engine fuels. In addition, it serves as an initial supporting document for the creation of the necessary quality control system.

Process design of cold forging with thick plate for seat recliner parts

A seat recliner is a device that connects the seat back with the seat frame. It can be used to adjust the lean angle. An important component of a seat recliner is the sector tooth, which has thus far been manufactured by the fine blanking process. In this study, we propose the use of the cold-forging process as an alternative in order to achieve improved mechanical stiffness and reduced weight. To apply the cold-forging process, the entire forming process is divided into two stages in order to improve the dimensional accuracy of the tooth part of the sector tooth. Uniform plastic deformation is induced by the design of the preform on the contacting area in the sector tooth by simultaneously using a bending and a forging mechanism. By the proposed process design for the two-step cold forging process, the mechanical stiffness and surface roughness of the test product can be improved. Furthermore, the weight can be reduced by 10% by applying a 3.6-mm-thick plate instead of a 4.0-mm-thick one. Finally, the number of forming stages can be reduced without sacrificing the dimensional accuracy of the sector tooth and increasing the punch load.

二段充てん法による内はすば歯車の成形

In a previous paper, we proposed a two-step cold extrusion method of shaping external spur gears and helical gears. In the present paper, we describe how this filling method is applied to the shaping of internal helical gears. A specially designed mandrel for an internal helical gear utilizing the two-step filling method was used to expand and the inner diameter of the cylindrical workpiece. The specifications of these gears are as follows: module m=1.0, 1.25 and 1.5 mm; helix angle ß=20 deg; number of teeth Z=12-15 and whole depth h=2.00 module. The materials used were aluminum A1200 and low carbon steel S15C. The criterion for shaping complete teeth is discussed primarily in terms of punch pressure and the reduction in the area and the expansion ratio of the inner diameter of the workpiece. The approach that we described here successfully produced a filled up internal helical gear with only a few percent reduction in area. The punch pressure was very low, far below the strength of the punch material.

Effects of Two-Step Cold Rolling on Recrystallization Behaviors in ODS Ferritic Steel

The recrystallization behaviors of Fe–15Cr ODS ferritic steels underwent two different processing routes were compared; (a) 1st 70% cold rolling + intermediate annealing, (b) 1st 70% cold rolling + intermediate annealing at 1100°C to make a recrystallization structure +2nd 70% cold rolling + final annealing. Hardness and texture changes during rolling and isochronal annealing were investigated. Results show that the recrystallization temperature of 70% cold rolled specimen is 950°C and the recrystallization texture is {111} . On the contrary, in the case of specimen which was cold rolled for two times, the recrystallization temperature increases to 1100°C, and the recrystallization texture changes to {111} . These changes are ascribed to the different routes of crystalline rotation during 1st and 2nd cold rolling, which produce different cold rolling texture. Higher {100} content induced by 2nd cold rolling after intermediate recrystallization which has low stored energy increases the recrystallization temperature. And the difference in texture intensity along γ fibre after 1st and 2nd cold rolling results in different recrystallization texture.

Study on a New Technological Scheme for Cold Press Forging Forming of Step Holes in Thick Sheet Metal

An new technological scheme for a two-step cold press forging of step holes in a thick metal sheet was proposed . Finite element analysis on the two-step process is carried out by using DEFORM-3D. Velocity shade contours are obtained. The study shows that the technique can form step holes in thick sheet metal and increase their strength, According to the numerical simulation’s process parameter, an experimental die is designed, the FEA results are in good agreement with the experimental data.

1208 二段充てん法による内歯車の成形(OS12-2高精度・高機能化加工技術)

1208 二段充てん法による内歯車の成形(OS12-2高精度・高機能化加工技術)