Carbon Fiber Breakage Mechanism in Aluminum(Al)/Carbon Fibers(CFs) Composite Sheet during Accumulative Roll Bonding(ARB) Process

We put forward a method of fabricating Aluminum(Al)/carbon fibers(CFs) composite sheets by the accumulative roll bonding(ARB) method. The finished Al/CFs composite sheet has CFs and pure Al sheets as sandwich and surface layers. After cross-section observation of the Al/CFs composite sheet, we found that the CFs discretely distributed within the sandwich layer. Besides, the tensile test showed that the contribution of the sandwich CFs layer to tensile strength was less than 11% compared with annealed pure Al sheet. With ex-situ observation of the CFs breakage evolution with-16%,-32%, and-45% rolling reduction during the ARB process, the plastic instability of the Al layer was found to bring shear damages to the CFs. At last, the bridging strengthening mechanism introduced by CFs was sacrificed. We provide new insight into and instruction on Al/CFs composite sheet preparation method and processing parameters.

Fabrication of ultrafine-grained AA1060 sheets via accumulative roll bonding with subsequent cryorolling

Ultrafine-grained(UFG)AA1060 sheets were fabricated via five-cycle accumulative roll bonding(ARB)and subsequent three-pass cold rolling(298 K),or cryorolling(83 K and 173 K).Microstructures of the aluminum samples were examined via transmission electron microscopy,and their mechanical properties were measured via tensile and microhardness testing.Results indicate that ultrafine grains in ARB-processed sheets were further refined by subsequent rolling,and the grain size became finer with reducing rolling temperature.The mean grain size of 666 nm in the sheets subjected to ARB was refined to 346 or 266 nm,respectively,via subsequent cold rolling or cryorolling(83 K).Subsequent cryorolling resulted in ultrafine-grained sheets of higher strength and ductility than those of the sheets subjected to cold rolling.

Analysis of bending on the front end of sheet during hot rolling

The analysis of bending in finishing rolling was performed. An asymmetrical rolling force model was established, and the upper and lower neutral points were determined. Thc bending which resulted from the asymmetrical rolling force at the roll gap was studied and related flexibility equations were proposed according to elastic mechanics. Moreover, material mechanics was used to analyze the effects of temperature difference and self-weight on the bending out of the roll gap, and the flexibility equations were constructed. The main factors on bending were summed up, and the bending rule in the rolling could be obtained. In addition practical calculation was made with the production data of ribbon steel from Laiwu Iron ＆ Steel Group Co. Ltd.

Microstructure evolution,mechanical properties and tailoring of coefficient of thermal expansion for Cu/Mo/Cu clad sheets fabricated by hot rolling

The law of microstructure evolution and mechanical properties of hot roll bonded Cu/Mo/Cu clad sheets were systematically investigated and the theoretical prediction model of the coefficient of thermal expansion(CTE)of Cu/Mo/Cu clad sheets was established successfully.The results show that the deformation of Cu and Mo layers was gradually coherent with an increase in rolling reduction and temperature and excellent interface bonding was achieved under the condition of a large rolling reduction.The development of the microstructure and texture through the thickness of Cu and Mo layers was inhomogeneous.This phenomenon can be attributed to the friction between the roller and sheet surface and the uncoordinated deformation between Cu and Mo.The tensile strength of the clad sheets increased with increasing rolling reduction and the elongation was gradually decreased.The CTE of Cu/Mo/Cu clad sheets was related to the volume fraction of Mo.The finite element method can simulate the deformation and stress distribution during the thermal expansion process.The simulation result indicates that the terminal face of the clad sheets was sunken inward.

An upper bound analysis of rolling process of non-bonded sandwich sheets

Rolling process of symmetrical non-bonded sandwich sheets was investigated by the method of upper bound. A deformation model was proposed and the mathematical relations of the velocity components were developed. The internal, shear and frictional power terms were derived and used in the upper bound model. Through the analysis, the rolling force, mean contact pressure and final thickness of each layer were determined. The validity of the proposed analytical model was discussed by comparing the theoretical predictions with the experimental data found in the literatures. Effects of various rolling conditions such as the flow stress ratio, initial thickness ratio of the raw sheets and total thickness reduction upon the rolling torque were analyzed. The accuracy of the developed analytical model was very high.

Texture Characteristics of Thin Grain Oriented Silicon Steel Sheet Produced by Cross Shear Rolling

Commercial grain oriented silicon steel was cold rolled to thickness from 0.06 to 0.10 mm by cross shear rolling, then annealed in vacuum or a hydrogen atmosphere furnace. Deformation textures of the sheets were researched by ODF method and reverse pole figure quantitative analyses. The results indicate that: in the condition of the cross shear rolling, the deformation texture of rolled sheet is generally similar to that of conventional rolled sheet, however, the texture distribution through the thickness is asymmetrical. With mismatch speed ratio increasing, the amount of Goss texture increases. With reduction ratio increasing, the intensity of γ-fiber becomes strong.

Microstructure and Mechanical Properties of Molybdenum Sheet after Cross Rolling Processing

A substantial body of work exists here that describe the relationship between the microstructure, ingot processing and fabrication and mechanical properties of molybdenum sheet after cross rolling process. The objective of this study is to clarify how much the crossing rolling process procedure affects the microstructure, texture and mechanical property of this type of materials. This experiment begins from the power metallurgy to the final molybdenum strip (0.15mmxlOOmmx2000mm) through the cross rolling processing procedure. As a result, good mechanical property, improved elongation, enhanced ductility for further process, such as deep drawing and punching, and the reduced difference of the strength and plasticity between the parallel to rolling direction and perpendicular to rolling direction are achieved by the cross rolling processing procedure. According to discussing all the details about this experiment, it is confirmed that cross rolling molybdenum sheet can provide a concise and comprehensive explanation of processes and can guarantee the optical mechanical property and suitable for large production.

Characterization of W80Cu20 alloy sheet prepared by hot-rolling

Multi-pass hot-rolling technique was used to fabricate W80Cu20 alloy,and its properties were characterized in this paper.Results show that the W-Cu alloy sheets with a thickness of 0.5 mm and a relative density of99.87%can be successfully made using this new technique at 800℃.In hot-rolling process,Cu phases are closely surrounded by W particles under the rolling stress to form a network microstructure,thus making significant increase in electrical and thermal conductivity up to53.00%and 24.44%,respectively.Transverse and longitudinal hardness of the W–Cu sheets significantly increase due to the enhanced densification and deformation strength.Similar to that of the raw materials,three fracture types were observed in the hot-rolled materials,i.e.,ductile fracture of Cu binding phases,trans-granular fracture of W phases,and W–W interfacial fracture.

Head Curvature of Pure Titanium Sheet Influenced by Process Parameters and Controlling in Hot Rolling Process

We investigated the influences of process parameters on the head curvature of pure titanium sheet in hot rolling process and proposed the controlling means. First, the thermal simulation experiments for pure titanium TA1 were carried out to investigate the hot deformation behaviors of pure titanium in the temperature range of 700-800 ℃ with strain rate range of 1-20 S-1, and the processing map was established to determine optimized deformation parameters. Then, the finite element model has been constructed and used to analyze the effect of process parameters on the direction and severity of head curvature of pure titanium sheet. The process parameters considered in the present study include workpiece temperature, work roll diameter, pass reduction, oxide scale thickness of workpiece surface, and interface friction coefficient. The simulation results show that the workpiece temperature and the interface friction coefficient are the two main factors. The proposed controlling means was carried out on a hot rolling production line and solved the head curvature problem effectively. The rolling practices indicate that the rolling yield is improved greatly.

The introduction and solvent of cold-rolling automobile sheet surface quality defects in BX Steel

The paper shows the main surface defects of cold rolling automobile sheet in BX Steel.The main surface defects are unusual defects.The typical familiar defects are sliver and punctuates that are on the rolling direction.The inclusions of steel-making and scales of hot rolling process are the main causes of defects.They are the biggest problems puzzle cold rolled automobile sheet surface quality,and are the burning issues of BX Steel.We classify and analysis the defects.We observe the panorama of surface defects using portable video microscopy apparatus,and clean the sample using ultrasonic shaker,analysis the defects pattern and chemical composition using scanning electron microscope.At present the primary defects that impacted cold rolled automobile sheet quality are dark sliver defects.We control the steel-making and hot rolling process aiming at the cause and position of defects making.We fine control the operating of steel ladle,gating,casting system and continuous casting machine in steelmaking process.The scale defect is reduced by controlling furnace,high pressure water descaling system and finish mill descaling in hot rolling process.Alone with the reforming and renewing of equipment,gathering producing experience,the cold rolled automobile sheet quality made in BX Steel is upgrading gradually.

Influence of rolling ways on microstructure and anisotropy of AZ31 alloy sheet

Two rolling ways,unidirectional rolling and cross rolling,were carried out on twin roll cast AZ31 alloy sheet to study the influence of strain path change on the evolution of the rolling microstructure and texture as well as the anisotropic properties of AZ31 alloy sheet with microscopy,X-ray diffraction technique and tensile tests.It is found that cross rolling gives rise to more uniform microstructure and stronger texture intensities compared with unidirectional rolling.The differences in the microstructure and texture intensities are reflected in the anisotropy characterized by the difference in the yield stress and the fracture elongation that were measured along directions in the rolling plane at angles of 0■,45■and 90■from the rolling direction.

Micro Crack of Aluminum Sheet During Cold Rolling

The micro crack of aluminum sheet during cold rolling lubricated with emulsions is investigated. Experi-ments show that micro cracks occur after cold rolling process and this is attributed to various parameters, for instance, the thin oxide film formed at the sheet surface. The micro crack spacing thus becomes an important parameter which deserves more concerns. The aspect ratio of these micro cracks is then analyzed theoreti-cally, which takes into consideration of the oxide fracture process. The good agreement between the obser-vations and the theoretical predictions validates the analysis. The approach can shed some new lights on the mechanical process of aluminium sheet during cold rolling.

Research and application on the automatic measuring device for testing transverse thickness difference of cold-rolling steel sheet

Many advanced technologies have been applied in developing the automatic measuring device for testing transverse thickness difference of cold-rolling steel sheet,such as the technologies of automatic control,sensor measurement,marking identification,photographic location,computer application and information transmission.This measuring device can measure the transverse thickness difference of the steel plate accurately and quickly,with a high detection level of automation.It is an effective detection equipment for transverse thickness control of steel plate.Horizontal width of steel plate measuring 0.8-1.4 m, horizontal measurement point positioning accuracy±0.02 mm,thickness range 0.2-2.0 mm, measurement accuracy within±1μm.

Effect of rolling and heat treatment on microstructure and properties of Ti-26 sheet

The effect of heat treatment and rolling process on the properties and microstructures of Ti-26(Ti-15V-3Al-3Cr-3Sn-Forming) sheet was studied. The results show that the best rolling temperature for Ti-26 alloy is in the temperature range from 900 ℃ to 950℃. Under this condition,the resistance of deformation and yield ratio are low and the alloy has better hot work ability. The alloy will achieve better mechanical properties and completely recrystallized β microstructure when the deformation ratio is not less than 60% and the solution temperature is 30 ℃ above the phase transformation temperature. The best heat treatment conditions are recommended as:790℃,30 min,AC or WQ followed by 510 ℃,10 h,AC. Under this heat treatment condition the strength of the Ti-26 alloy is 1 230 MPa and the elongation is 15%.

Fatigue properties of pack ply-rolling Ti-6Al-4V alloy sheets

The influence of pack ply-rolling process and heat-treatment on the texture characteristics of Ti-6Al-4V alloy sheets was investigated applying the EBSD technique. The tensile properties and fatigue properties of the sheets possessing different type textures were measured. The results show that the alloy sheets possessing single type texture(B or T) exhibit lower fatigue strength compared with the mixed texture(B/T). The sheet possessing basal texture exhibits isotropy and its elastic modulus and yield strength are lower than those under other conditions.

Effect of calcium addition on microstructure and texture modification of Mg rolled sheets

The mechanical properties and texture of AM60（Mg-6.0Al-0.3Mn,mass fraction %） and ZXM200（Mg-1.6Zn-0.5Ca-0.2Mn） Mg alloys subjected to multi-pass hot rolling were investigated.The finer recrystallized grains usually exhibit particular preferred orientations and then alter the total texture feature of rolled sheets.Ca solid solution into Mg matrix serves to the formation of texture component with c-axis rotated away from normal direction towards transverse direction and then weakens the overall texture intensity,resulting in a similar anisotropic characteristic to RE-containing Mg alloys.

STUDY OF ROLLING FORCE DISTRIBUTION ALONG THE ROLLING OF PAIR CROSS MILL

The theory of three-dimensional deformation is used.Based on rigid plastic assumption, the theory of stick friction and the sheet crown curve at the entry and the exit are used. The mathematical analytical formula of the rolling force in lateral distribution is deriven.

A novel micro-rolling&incremental sheet forming hybrid process:Deformation behavior and microstructure evolution

Thin-walled metal parts with functional micro-featured surface have broad application prospects in the fields of resistance reduction,noise reduction,etc.In this study,a novel micro-rolling&incremental sheet forming hybrid process(μR-ISF)is proposed to fabricate thin-walled metal parts with microgroove arrays.An analytical model which relates the rolling force and microgroove depth in the micro-rolling stage was first established.Then,the formation mechanism of microgroove morphology during both micro-rolling stage and macro-shape forming stage are investigated.After the micro-grooved sheet being incrementally formed,a significant reduction(between 21%to nearly 60%)is occurred in the depth of both transverse and longitudinal grooves compared to the flat sheet.Meanwhile,the width of transverse grooves decreases slightly by about 10%on average,while the width of longitudinal microgrooves increases significantly by more than 30%on average.After micro-rolling,85°{102}tensile twins appear on the micro-grooved sheet and the percentage of 65°{112}compressive twins increases.After incremental forming,the percentage of low-angle grain boundaries and the density of geometrically necessary dislocations in the formed part increase significantly,and the grain size distribution becomes more uniform.The present work provides a new strategy for the fabrication of 3D metal thin-walled components with surface micro-features.

Effects of trace Gd concentration on texture and mechanical properties of hot-rolled Mg-2Zn-xGd sheets

The effects of Gd concentration(0.1,0.3,0.7 wt%)on the microstructure,texture and mechanical properties of rolled and annealed Mg-2Zn-xGd sheets have been investigated aiming to develop low cost and high ductile Mg-Zn-Gd sheets.Dynamic recrystallization,static recrystallization and grain growth during hot rolling process and annealing process were delayed with increase of Gd concentration,leading to fine grain microstructure.The rolled 0.1 wt%Gd sheet showed strong basal texture which remained stable after annealing process and exhibited medium elongation of about 25%.In contrast,the rolled 0.3 wt%Gd sheet had weak basal texture which transformed to non-basal texture with double peaks tilted about±48°to the transverse direction due to the static recrystallization during annealing process.Consequently,the annealed sheets exhibited higher elongation of 40%along the rolling direction and 50%along the transverse direction due to the existence of non-basal texture.It is suggested that the minimum effective concentration for texture randomization in the Mg-2Zn-xGd alloy is about 0.3 wt%.

Effect of hot rolling on microstructure and properties of the ZEK100 alloy

Attempts to expand manufacturing capabilities of magnesium-based sheet materials are described.The as-cast ZEK100(Mg-1.2Zn-0.35Zr-0.17Nd,in wt%)magnesium alloy was subjected to hot rolling at temperatures from 350℃to 450℃using the laboratory 50 ton reversible mill with preheated rolls to manufacture the 1.5-1.7 mm thick sheet.The rolling temperature affected the sheet properties and an increase in the rolling temperature from 250 to 450℃caused reduction of tensile strength from 257 to 228 MPa ac-companied by a reduction in tensile yield stress from 237 to 185 MPa.At the same time,the alloy elongation increased from 17 to 21%.For the same rolling temperature range,the compressive strength reduced from 418 to 351 MPa.The post-rolling annealing at 450℃led to reduction of both tensile and compressive properties with the largest changes corresponding to the rolling temperature of 350°C.The correlation between the alloy grain size after rolling and the sheet properties was established where a reduction in grain size was accompanied by an increase of both the tensile/compressive strength and yield stress.Based on Hall-Petch relationship and an average grain size the correlation developed in this study may be used as the prediction model for properties of the hot rolled magnesium sheet.The results are discussed in terms of recent developments in magnesium sheet alloys and the vital role played in this process by rare earth elements.