Improving the room-temperature bendability of Mg-3Al-1Zn alloy sheet by introducing a bimodal microstructure and the texture re-orientation

A significant enhancement of bendability was achieved by the introduction of bimodal microstructure for AZ31B alloy sheets via pre-compression and subsequent annealing(PCA)process.This combined treatment led to the c-axis of the extracted samples that were inclined by 30°to the rolling direction(30°sample)further shifting toward the rolling direction(RD)and resulting in a higher Schmid factor(SF)value of basal slip under the RD tensile stress.Furthermore,the bimodal microstructure that was introduced by the PCA process broke the damage bands(DBs)in the initial hot rolled AZ31B alloy sheets and gave rise to a more uniform strain distribution in the outer tension region of the bending samples,in which the tensile deformation was accommodated by the equally distributed{101^(-)2}tension twinning and basal slip.Consequently,the bimodal microstructure,shifted basal texture and the modification of DBs were responsible for the significant enhancement in the bendability of the AZ31 alloys.

Utilization of surface nanocrystalline to improve the bendability of AZ31 Mg alloy sheet

A surface nanocrystalline was fabricated by ultrasonic shot peening(USSP)treatment at AZ31 Mg alloy.The effect of nanocrystalline thickness and its placed side(external or internal)on the bendability was studied by a V-bending test.Three durations,5,10,and 15 min,were applied to form the surface nanocrystalline with thicknesses of 51,79,and 145μm,respectively.Two-side treatment led to a similar bendability as that of as-received.One-side internal treatment for 5 min resulted in an improved bendability while the improvement was limited and degenerated for longer treatment.The improvement was related to the drawing back of the neutral axis.The one-side external treatment also improved the bendability,and the improvement was due to the redistribution of strain and stress during bending.With nanocrystalline at external side,it resulted in a larger stress but a smaller strain at the convex,which prevented the happening of crack during bending.

Study on the bendability and toughness of a 1 500 MPa cold-rolled martensitic sheet steel

Cold rolled martensitic sheet steels are achieving more and more applications in car-making because of their ultra-high strength and potential for weight reduction. The relatively low plasticity of ultra-high strength martensitic steels might be a drawback for the applications in the aspects of forming and safety protection function and should be significantly noted. A 1 500 MPa grade cold rolled martensitic sheet steel has been studied to investigate the bendability at 90 degree bending and impact toughness as well as fracture surface morphology at various temperatures. Some discussions have been made basing upon the experiment data to get some understanding on the performance of the materials under various conditions and on how to make use of this kind of ultra high strength steel properly.

Development of a hot-rolled 980 MPa advanced high-strength steel with excellent flangeability and bendability

A new 980 MPa advanced high-strength steel(AHSS) with excellent bendability and flangeability has been studied and industrially produced, typical of tensile strength, fractured elongation, and hole expansion ratio(HER) exceeding 980 MPa, 10%,and 30%,respectively.The 90° V-type bending perpendicular to the rolling direction can satisfy the R/t=1.0 requirement, indicating excellent bendability.Systematic evaluations of industrial trial-produced 980 MPa hot-rolled AHSS have been conducted, including microstructure, tensile properties in three directions, HER,bendability, fatigue limit strength, and forming limit.The microstructure of the newly developed 980 MPa AHSS primarily consists of fine bainite and a small amount of martensite-austenite constituent.The practical yield and tensile strength are higher than 800 and 980 MPa, respectively, with typical elongation of 13% and HER of around 40%.The good combination of the newly developed 980 MPa AHSS is primarily attributed to the fine bainitic microstructure, resulting in excellent flangeability and bendability.In addition, the newly developed 980 MPa AHSS has good fatigue and forming properties, making it suitable for the production of chassis and suspension components.

A Study on Multi-defect Constrained Bendability of Thin-walled Tube NC Bending Under Different Clearance

Thin-walled tube numerical control （NC） bending is a tri-nonlinear physical process with multi-defect and multi-die constraints. The clearance on each contact interface is the major factor to indicate the contact conditions. A three-dimensional-finite element （3D-FE） model is established to consider the realistic dynamic boundary conditions of multiple dies under ABAQUS/Explicit platform. Combined with experiment, numerical study on bending behavior and bendability under different clearance between tube and various dies is conducted in terms of wrinkling, wall thinning and cross section deformation. The results show that （1）with smaller clearance of tube-wiper die and tube-mandrel, the wrinkling can be restrained while the wall thinning It and cross-section deformation Id increase; while excessive small clearance blocks tube materials to flow past tangent point and causes piles up, the onset of wrinkling enhances It and Id. （2）Both It and Id decrease with smaller clearance of tube-pressure die; the wrinkling possibility rises with larger clearance on this interface if the mandrel’s freedom along Y-axis is opened; smaller clearance of tube-bend die prevents wrinkling while increases It, and the clearance on this interface has little effect on Id. （3）A modified Yoshida buckling test （YBT） is used to address the wrinkling mechanisms under normal constraints in tube bending： the smaller clearance may restrain wrinkling efficiently; the smaller wall thickness, the less critical clearance needed; the critical clearance for tube bending 38 mm×1 mm×57 mm （tube outer diameter×wall thickness×centerline bending radius） equals about 20% of initial wall thickness.

Comparison of microstructures and mechanical properties of composite extruded AZ31 sheets

The microstructures and mechanical properties of the composite extruded AZ31/AZ31 and AZ31/4047 Al sheets were investigated and made a comparison to the conventional extruded AZ31 sheet.Owing to the introduced intense shear deformation at the interface during the composite extrusion,grain refinement and tilted texture were detected in AZ31 layers of the AZ31/AZ31 and AZ31/4047 Al sheets,while the conventional extruded AZ31 sheet exhibited a relative coarse,inhomogeneous microstructure and strong basal texture.The compressiontension yield ratio was increased gradually from the AZ31 to the AZ31/AZ31 and AZ31/4047 Al sheets.Besides,the AZ31/4047 Al sheet could successfully accomplish the whole bending forming process at room temperature,while the AZ31 and AZ31/AZ31 sheets were both bend-formed to failure with significant cracks in the outer tensile region under the identical bending parameters.Moreover,under the same bending strain,both the outward offset degree of strain neutral layer and the sheet thickening were more serious in the AZ31/4047 Al composite sheet than those of the AZ31 and AZ31/AZ31 sheets.The foremost reason was the quite wide gap of material properties between Mg alloy AZ31 layer(tensile loading in the outer region)and Al 4047 layer(compressive loading in the inner region).

Effects of quenching and over-aging temperatures on mechanical properties of ultra-high strength cold-rolled martensite steels

As cold-formed steel has the highest strength-to-weight ratio of any material,ultra-high strength martensitic steel is attracting great interest from global car manufacturers. This paper explores the effects of the quenching and over-aging temperatures on the strength and cold bendability of C-Mn-Si martensitic steel. Due to its high carbon content,water-quenched C-Mn-Si martensitic steel has high hardenability and can obtain ultra-high tensile strength and uniform martensitic morphology when the water-quenching temperature is higher than 710 ℃.Increasing the over-aging temperature of this experimental steel decreases its tensile strength,increases the total elongation,and first increases then decreases the yield point until reaching a peak at 180 ℃. Besides,when increasing the over-aging temperature,the bendability of this experimental steel initially improves and then decreases,and reaches its optimal bendability at an over-aging temperature of 180 ℃. Based on SEM characterization and a microhardness distribution analysis,the over-aging temperatures were found to affect the size of the carbides and differences in the microhardness of the experimental steel. Therefore,they have significant influence on bendability.

Recent progress of efficient flexible solar cells based on nanostructures

Flexible solar cells are important photovoltaics(PV)technologies due to the reduced processing temperature,less material consumption and mechanical flexibility,thus they have promising applications for portable devices and building-integrated applications.However,the efficient harvesting of photons is the core hindrance towards efficient,flexible PV.Light management by nanostructures and nanomaterials has opened new pathways for sufficient solar energy harvesting.Nanostructures on top surfaces provide an efficient pathway for the propagation of light.Aside from suppressing incident light reflection,micro-structured back-reflectors reduce transmission via multiple reflections.Nanostructures themselves can be the absorber layer.Photovoltaics based on high-crystallinity nanostructured light absorbers demonstrate enhanced power conversion efficiency(PCE)and excellent mechanical flexibility.To acquire a deep understanding of the impacts of nanostructures,herein,a concise overview of the recent development in the design and application of nanostructures and nanomaterials for photovoltaics is summarized.

The relevance of Niobium microalloying in dual phase steels with optimized mechanical properties

Dual phase steel is nowadays widely applied in automotive construction as hot rolled and cold rolled HDG grades.The strength and elongation of DP steels are principally determined by the ratio of ferrite and marteniste in the microstructure.However,for practical forming in the press shop additional properties are important such as bendability and hole expansion ratio.These characteristics relate to the morphology and distribution of the phases in the microstructure.Niobium microalloying can influence not only the strength of DP steels but also particularly the phase morphology and homogeneity leading to significant improvement of the mechanical properties.The paper will show processing strategies involving Nb microalloying in DP steel production.The metallurgical mechanisms induced by Nb are discussed.This is also related to damage mechanisms occurring in DP steel during forming or application.Particularly the issue of delayed fracturing in ultra high strength DP steel will be addressed.

Bendable tube-shaped supercapacitor based on reduced graphene oxide and Prussian blue coated carbon fiber yarns for energy storage

Carbon fiber yarns（CFY） are promising as a new type of flexible building blocks for the construction of flexible architectures for the energy storage applications. The main hurdle with CFY is how to make them high energy and power capable by using economically and environmentally viable materials. Here,we report reduced graphene oxide（r GO） and Prussian blue（PB） coated CFY, derived from a facile electrochemical process at room temperature for supercapacitor electrodes. The PB coated CFY and r GO coated CFY electrodes exhibit the excellent gravimetric capacitance of 339 F/g and 160.2 F/g, respectively, in aqueous KCl electrolyte in three-electrode cell configuration. When we coupled these electrodes inside the flexible plastic tube and separated by the electrolyte wet filter paper in order to construct flexible architecture, the resulting device delivers excellent specific energy of 52.1 Wh/kg and 26.5 Wh/kg with offering specific power of 3100 W/kg and 14400 W/kg respectively, under a wide operating potential of1.8 V with excellent rate capability. The device shows high tolerance towards bending, and retained its efficiency to the capacitance after being bent at an angle of 360° for 200 bending cycles.

High-Quality Bi_2Te_3 Single Crystalline Films on Flexible Substrates and Bendable Photodetectors

Recently, great efforts have been made in the fabrication of arbitrary warped devices to satisfy the requirement of wearable and lightweight electronic products. Direct growth of high crystalline quality films on flexible substrates is the most desirable method to fabricate flexible devices owing to the advantage of simple and compatible preparation technology with current semiconductor devices, while it is a very challenging work, and usually amorphous, polycrystalline or discontinuous single crystalline films are achieved. Here we demonstrate the direct growth of high-quality Bi2 Te3 single crystalline films on flexible polyimide substrates by the modified hot wall epitaxy technique. Experimental results reveal that adjacent crystallites are coherently coalesced to form a continuous film, although amounts of disoriented crystallites are generated due to fast growth rate. By inserting a quartz filter into the growth tube, the number density of disoriented crystallites is effectively reduced owing to the improved spiral interaction. Furthermore, flexible Bi2 Te3 photoconductors are fabricated and exhibit strong near-infrared photoconductive response under different degrees of bending, which also confirms the obtained fexible films suitable for electronic applications.

Nanowatt power operation of silicon nanowire NAND logic gates on bendable substrates

In this paper, we propose a novel construction of silicon nanowire （SiNW） negative-AND （NAND） logic gates on bendable plastic substrates and describe their electrical characteristics. The NAND logic gates with SiNW channels are capable of operating with a supply voltage as low as 0.8 V, with switching and standby power consumption of approximately 1.1 and 0.068 nW, respectively. Superior electrical characteristics of each SiNW transistor, including steep subthreshold slopes, high Ion/off ratio, and symmetrical threshold voltages, are the major factors that enable nanowatt-range power operation of the logic gates. Moreover, the mechanical bendability of the logic gates indicates that they have good and stable fatigue properties.

Low-power functionality of silicon-nanowire-assembled inverters on bendable plastics

In this paper, we demonstrate the low-power functionality of silicon nanowire （SiNW）-assembled inverters on bendable plastics. Our bendable inverters are capable of operating at supply voltages as low as 0.8 V with a switching （or standby） power consumption of -0.2 nW （or -6.6 pW）. The low-power inverting operation with a voltage gain of -18 is attributable to the near-ideal characteristics of the component transistors that have selectively thinned SiNW channels and exhibit low, symmetrical threshold voltages of 0.40 and -0.39 V and low subthreshold swing values of 81 and 65 mV/dec. Moreover, mechanical bendability reveals that the inverting operation has good, stable fatigue properties.

Silicon nanowire CMOS NOR logic gates featuring onevolt operation on bendable substrates

In this study, we propose complementary metal-oxide-semiconductor （CMOS） NOR logic gates consisting of silicon nanowire （NW） arrays on bendable substrates. A circuit consisting of two p-channel NW field-effect transistors （NWFETs） in series and two n-channel NWFETs in parallel is constructed to operate a two- input CMOS NOR logic gate. The NOR logic gates operate at a low supply voltage of 1 V with a rail-to-rail logic swing and a high voltage gain of approximately -3.0. The exact NOR logic functionality is achieved owing to the superior electrical characteristics of the well-aligned p- and n-NWFETs, which are obtained using conventional Si-based CMOS technology. Moreover, the NOR logic gates exhibit stable characteristics and have good mechanical properties. The proposed bendable NW CMOS NOR logic gates are promising building blocks for future bendable integrated electronics.

Silicon nanowire ratioed inverters on bendable substrates

In this study, we demonstrate the performance of silicon nanowire （SiNW） n-metal oxide semiconductor （MOS） and p-MOS ratioed inverters that are fabricated on bendable substrates. The electrical characteristics of the fabricated devices can be controlled by adjusting the load voltage. The logic swings of the n- and p-MOS ratioed inverters at a low supply voltage of 1V are 80% and 96%, respectively. The output voltage level of the p-MOS ratioed inverter is close to rail-to-rail operation. The device also exhibits stable characteristics with good fatigue properties. Our bendable SiNW ratioed inverters show promise as a candidate building block for future bendable electronics.