Effects of cold deformation on microstructure and mechanical properties of Ti-35Nb-2Zr-0.3O alloy for biomedical applications

The Ti-35Nb-2Zr-0.3O(mass fraction,%)alloy was melted under a high-purity argon atmosphere in a high vacuumnon-consumable arc melting furnace,followed by cold deformation.The effects of cold deformation process on microstructure andmechanical properties were investigated using the OM,XRD,TEM,Vicker hardness tester and universal material testing machine.Results indicated that the alloy showed multiple plastic deformation mechanisms,including stress-inducedα'martensite(SIMα')transformation,dislocation slipping and deformation twins.With the increase of cold deformation reduction,the tensile strength andhardness increased owing to the increase of dislocation density and grain refinement,and the elastic modulus slightly increasedowing to the increase of SIMα'phase.The90%cold deformed alloy exhibited a great potential to become a new candidate forbiomedical applications since it possessed low elastic modulus(56.2GPa),high tensile strength(1260MPa)and highstrength-to-modulus ratio(22.4×10-3),which are superior than those of Ti-6Al-4V alloy.

Effect of B_(4)C on strength coefficient,cold deformation and work hardening exponent characteristics of Mg composites

The emphasis of this exploration was to examine the workability and work hardening performance of Mg(Magnesium)specimen and Mg-B_(4)C composites created via the powder metallurgy technique.The pure Mg and Mg-B_(4)C composites are made with distinct weight percentages(Mg-5%B_(4)C,Mg-10%B_(4)C,and Mg-15%B_(4)C)at the unit aspect ratio.The powders and composites characterization are executed by SEM(Scanning Electron Microscope),EDS(Energy Dispersive Spectrum)with an elemental map,and XRD(X-ray Diffraction)examination.It displays that,the B_(4)C particles were dispersed consistently with the Mg matrix.The workability and work hardening examination was conducted in triaxial stress conditions using the cold deformation process.The consequence of workability stress exponent factor(β_(σ)),distinct stress proportion factors(σ_(m)/σ_(eff)and σ_(θ)/σ_(eff)),instantaneous work hardening exponent(n_(1)),work hardening exponent(n),coefficient of strength(k)and instantaneous coefficient of strength(k_(1))are recognized.The outcome displays that Mg-15%B_(4)C specimen has greater workability and work hardening parameter,initial relative density,and triaxial stresses compared with the Mg specimen and Mg-(5–10%)B_(4)C composites.

Influence of chemical composition and cold deformation on aging precipitation behavior of high nitrogen austenitic stainless steels

The influence of chemical composition and cold deformation on aging precipitation behavior of 18Cr-16Mn-2Mo-I.IN （HNS-A）, 18Cr-16Mn-I.3N （HNS-B）, 18Cr-18Mn-2Mo-0.96N （HNS-C） and 18Cr-18Mn-2Mo-0.77N （I-INS-D） high nitrogen austenitic stainless steels was investigated. The results show that the ＂nose＂ temperatures and incubation periods of the initial time-temperature-precipitation （TTP） curves of aged HNSs are found to be 850 ℃, 60 s; 850 ℃, 45 s; 850 ℃, 60 s and 900 ℃, 90 s, respectively. Based on the analysis of SAD patterns, the coarse cellular Cr2N precipitate which presents a lamellar structure has a hexagonal structure of a=0.478 nm and c=0.444 nm. The Z phase corresponding to a composition of Fe36Cr^2Mo10, is determined to be a body-centered cubic structure ofa=0.892 nm. The precipitating sensitivity presents no more difference with the nitrogen content increasing from 0.77% to 0.96%, but exhibits so obviously that the cellular precipitates nearly overspread the whole field. The addition of Mo element can restrain the TTP curves moving left and down, which means decreasing the sensitivity of aging precipitation. With increasing the cold deformation, the sensitivity of precipitation increases obviously.

The effect of structure and property of TP347H steel tube for cold deformation

In recent years,with the rapid increase in national electricity demand and energy-saving environmental protection requirements to further improve and develop high-capacity,high efficiency,ultra (ultra) supercritical thermal power units parameter is the current mainstream trends.TP347H austenitic heat-resisting steel as good high temperature oxidation resistance,creep resistance,intergranular corrosion,and excellent welding and hot and cold processing has been widely applied to power plant maintenance and major domestic supercritical capacity power plant boilers.Cold process is important in the production of seamless steel tube.This paper aims at TP347H steel tube,used by high-preesure boiler.Through the studying the effect of cold deormation of steel tube on grain size and mechanical properties at room temperature and solution state,giving reasonable supports for developing the cold process of TP347H steel tube.Through study found that the increasing cold size results to thinner steel crystals and the line slip in the topaz.When the cold size come up to 15%,20%,room temperature as the same as flow of yield strength and intensity increase.In mixed condition of solid and liquid,the line slip in the topaz disappears,as the increasing cold size,room temperature as the same as flow of yield strength and intensity decrease,of the orb of the same thin,and yield strength to strength and pulled all possible.In the same temperature,with cold size increased,the shape of the yield strength to strength,and the extension section of the laws not change significantly.At the same amount as shape,keola the temperature increases,high yield strength and pulled out to reduce intensity.

Influence of cold deformation on microstructure,mechanical properties,and corrosion resistance of high-sulfur free-cutting 316LS stainless steel

In this study,the influence of plastic deformation produced by cold rolling at reduction ratios ranging from 10% to 80% on the microstructure,mechanical properties,and pitting corrosion behavior of high-sulfur freecutting 316 LS austenitic stainless steel was investigated. The results indicate that slipping is the predominant effect and that sulfide inclusions extend along the rolling direction during the cold deformation of 316 LS. The strong austenite stability of 316 LS results in the formation of only a small quantity of deformation-induced martensite. The experimental results reveal that the strength,hardness,and yield ratio increased with increases in the reduction ratio,mainly due to work hardening,whereas the elongation decreased drastically,due to the combined effect of the work hardening and brittleness caused by the numerous sulfide inclusions. Electrochemically active sites on the surface of316 LS increased with an increased reduction ratio,which caused an increased current fluctuation in the passive zone. This also caused the breakdown potential（ E_b） near the pitting zone to exhibit a gradual increase in the zigzag current shift to the left on the polarization curves. The E_b of 316 LS decreased with increases in the reduction ratio,mainly due to the extended sulfide inclusions,the increased dislocation density,and the deformation-induced martensite content.

Influence of Cold Deformation on the Aging Behaviour of Al-Cu-Si-Mg Alloy

The present study deals with the effect of cold deformation and subsequent aging on the microstructure and mechanical properties of AI-Cu-Si-Mg alloy. Differential scanning calorimetry indicates that precipitation occurs in the temperature range of 258-272℃ for the as quenched wrought alloy. The activation energy value estimated by Kissinger method for the aforesaid precipitation reaction is obtained as 106 kJ/mol. 45% cold deformation prior to aging indicates the first dissolution reaction at about 50℃ and the precipitation reaction at a temperature of about 82℃. Microstructural investigations have revealed the formation of fine precipitates within the matrix after aging of the cold deformed sample. As-quenched alloy reveals prominently the aging response, The increase in hardness, yield and tensile strength with simultaneous decrease in elongation in the deformed alloy is found to be primarily due to the deformation strengthening and not due to the precipitation hardening.

Effect of cold deformation on corrosion fatigue behavior of nickel-free high nitrogen austenitic stainless steel for coronary stent application

Due to the excellent mechanical properties, good corrosion resistance, high biocompatibility and nickel- free character, the high nitrogen nickel-free austenitic stainless steel （HNASS） becomes an ideally alternative material for coronary stents. Stent implantation works in harsh blood environment after a balloon dilatation, i.e., the material is used in a corrosive environment with a permanent deforma- tion. The present study attempts to investigate effects of pre-straining on high-cycle fatigue behavior and corrosion fatigue behavior of HNASS in Hank＇s solution and the relevant mechanism for coronary stents application. It is found that higher pre-straining on HNASS results in higher strength and maintains almost same corrosion resistance. Fatigue limit of 0% HNASS is 550 MPa, while corrosion fatigue limit is 475 MPa. And improvement in fatigue limit of 20% and 35% pre-strained HNASS is in comparison with the 0% HNASS, while corrosion would undermine the fatigue behavior of HNASS. In a suitable range, the pre- straining had a beneficial effect on corrosion fatigue strength of HNASS, such as nearly 300 MPa improved with 20% cold deformation. This result provides a good reference for predicting the life of HNASS stent and as well its design.

Effects of cold rolling deformation on microstructure,hardness,and creep behavior of high nitrogen austenitic stainless steel

Effects of cold rolling deformation on the microstructure, hardness, and creep behavior of high nitrogen austenitic stainless steel （HNASS） are investigated. Microstructure characterization shows that 70% cold rolling deformation results in significant refinement of the microstructure of this steel, with its average twin thickness reducing from 6.4 μm to 14 nm. Nanoindentation tests at different strain rates demonstrate that the hardness of the steel with nano-scale twins （nt-HNASS） is about 2 times as high as that of steel with micro-scale twins （mt-HNASS）. The hardness of nt-HNASS exhibits a pronounced strain rate dependence with a strain rate sensitivity （m value） of 0.0319, which is far higher than that of mt-HNASS （m = 0.0029）. nt-HNASS shows more significant load plateaus and a higher creep rate than mt-HNASS. Analysis reveals that higher hardness and larger m value of nt-HNASS arise from stronger strain hardening role, which is caused by the higher storage rate of dislocations and the interactions between dislocations and high density twins. The more significant load plateaus and higher creep rates of nt-HNASS are due to the rapid relaxation of the dislocation structures generated during loading.

Effect of Cold Deformation on the Friction–Wear Property of a Biomedical Nickel-Free High-Nitrogen Stainless Steel

The microstructural,mechanical and corrosion properties of different cold-rolled biomedical nickel-free highnitrogen stainless steels（NFHNSSs） were investigated to study the effect of cold deformation on its dry wear resistance as well as corrosion–wear behaviors in distilled water and Hank＇s solution. The results indicated that NFHNSS was characterized by stable austenite and possessed excellent work-hardening capacity; due to increasing cold deformation,the corrosion resistance just decreased very slightly and the dry wear rate decreased initially but subsequently increased,while the corrosion–wear resistance was improved monotonically in both distilled water and Hank＇s solution in spite of the presence of corrosive ions. The friction coefficients for different cold-rolled NFHNSSs were very close under the same lubricating condition,but they were the largest in distilled water compared to that in dry wear tests and Hank＇s solution.

Effect of Cold Deformation on Phase Evolution and Mechanical Properties in an Austenitic Stainless Steel for Structural and Safety Applications

The effects of cold deformation on the formation of strain induced α’ martensite and mechanical properties of an austenitic stainless steel have been examined.X-ray diffraction analysis has revealed that 30% and 40% cold rolling have resulted in the formation of 24% and 31.5% martensite respectively.Microstructural investigation has demonstrated that the formation of martensite is enhanced with increase in the percent deformation at 0 ℃.Investigation of mechanical properties reveals that hardness,yield strength and tensile strength values increase where as percent elongation drops with increasing deformation.The fractographic observation corroborates the tensile results.Examination of sub-surface at the fractured end of the tensile sample manifests that void/microcrack nucleation occurs in the interfacial regions of the martensite phase as well as at the austenite-martensite interface

Properties and microstructure of Ti6Al4V by deformation accelerated low temperature plasma nitriding

An integrated low-temperature nitriding process was carried out for Ti6Al4V to investigateitseffect on microstructure and properties.The process was designed to enhance the nitriding kinetics in low-temperature（500℃） nitriding by deformation, and to strengthen Ti6Al4V alloybydispersionat the same time. Specimens of Ti6Al4V alloyweretreated through the process of solid solutionstrengthening-cold deformation-nitriding at 500℃. The white nitriding layeris formed after some time and then kept stable, changing little withthedeformationdegreeand time. The effect of aging on substrate is significant. Surface hardness and substrate hardnessincrease with deformation increasing. The construction was investigated by XRD.The surface nitridesare TiN, Ti2N, Ti4N3-Xand Ti3N1.29,and thenitridesin cross-section are Ti3N1.29and TiN0.3. The wear tests of specimens after nitriding, aging and deformation were carried out,andthetest data show that the nitrided pieces have the best wear resistance.

Quantitative contributions of solution atoms, precipitates and deformation to microstructures and properties of Al-Sc-Zr alloys

In order to investigate the effects of solid solution atoms, precipitated particles and cold deformation on the microstructures and properties of Al-Sc-Zr alloys, the Al-Sc-Zr alloys prepared by continuous rheo-extrusion were treated by thermomechanical treatment, analyzed for conductivity and mechanical properties by tensile and microhardness testing, and characterized using optical microscope, TEM and STEM. A mathematical model was established to quantitatively characterize the contribution of solid solution atoms, precipitates and cold deformation to the conductivity of the alloy. The results show that the strength of Al alloy can be significantly improved by solid solution, aging and cold deformation, and the quantitative impacts of solution atoms, precipitates and cold deformation on the conductivity of Al alloy are 10.5%(IACS), 2.3%(IACS) and 0.5%(IACS), respectively. Aging and cold deformation treatments are the keys to obtain high-strength and high-conductivity aluminum alloy wires.

Evolution of microstructure, phase composition, and tensile properties of severely cold deformed titanium metastable β alloy in rapid continuous heating

Influence of severe cold deformation of titanium alloy Ti-1.5%A1-6.8%Mo-4.5%Fe in metastable β condition on the evolution of phase composition, microstructure, and tensile properties during continuous rapid heating was studied. As-deformed alloy was characterized by quasi-amorphous single-phase β condition with an abnormal temperature dependence of electric resistance that was normalized after 48 h exposure at room temperature as a result of isothermal ω phase precipitation. Subsequent rapid heating with a rate of 5 ℃/s caused recovery and recrystallization. Tensile properties of the alloy after different treatments were determined and discussed.

Wear resistance of TC4 by deformation accelerated plasma nitriding at 400 °C

An integrated low temperature nitriding process for TC4（Ti6Al4V） has been developed and the effect on wear resistance has been investigated. Through the process of solid solution strengthening—cold deformation—nitriding at 400℃, the TC4 alloy is nitrided on surface and dispersion strengthened in bulk at the same time. The white nitriding layer is formed after some time of nitriding. The nitriding speed increases with the deformation degree. The construction was investigated by XRD and the nitride is Ti3N（2-X）. The wear test was carried out and results exhibit that the nitrided samples have better wear resistance.

Recrystallization of the cold-deformed discontinuous precipitation microstructure in Al-Zn (-Cu) alloys

Recrystallization of cold-rolled discontinuous, precipitation microstructurewhich has fine laminar structure in an Al-40 percent Zn (atom fraction) binary alloy is investigatedby optical microscopy, SEM and TEM. It is found that there are two kinds of recrystallizationmechanisms: continuous coarsening (CC) and discontinuous coarsening (DC). The latter can be dividedinto coarsening mainly driven by stored deformation energy at colony boundaries and slip bands andthe one mainly driven by boundary energy in the area with little deformation. It is shown that theaddition of Cu can retard the nucleation of coarsening cells and their growth. X-Ray diffractionanalysis indicated the metastable phase CuZn_4 transformed into equilibrium phase A;_4Cu_3Zn duringthe heating process.

Effect of Mo and cold forging deformation on strength and ductility of cobalt-based alloy L605

Mo element was added to cobalt-based alloy L605,and cold forging deformation was performed.The effects of the addition and cold forging deformation on the microstructure and mechanical properties of the alloy were studied by thermodynamic calculation,electron backscatter diffraction,transmission electron microscopy,and X-ray diffraction.The stacking fault energy(SFE)of the alloy decreased after the addition,and the formation of stacking faults and intersections were promoted to improve the strength and hardness.The tensile strength of the alloy with Mo increased from 1190 to 1702 MPa after 24%cold deformation,producing significant work hardening.The strengthening mechanism is strain-induced martensitic transformation(SIMT)and deformation twinning.The alloy,combined with Mo and after 24%deformation,had both high strength and ductility in comparison with the original cobalt-based alloy L605.This is attributed to the lower SFE which caused the increase in stacking fault density.During the tensile process,theε-hcp phase was easily generated at the stacking fault to reduce the stress concentration and increase the ductility.Controlling SIMT by adjusting the density of stacking faults can improve the mechanical properties of cobalt-based alloys.Theε-hcp phase,the interaction between deformation twins and dislocations,and the interaction between e-hcp phases during cold forging deformation caused local stress concentration,lowering ductility and toughness.

High-precision Thickness Setting Models for Titanium Alloy Plate Cold Rolling without Tension

Due to its highly favorable physical and chemical properties,titanium and titanium alloy are widely used in a variety of industries.Because of the low output of a single batch,plate cold rolling without tension is the most common rolling production method for titanium alloy.This method is lack of on-line thickness closed-loop control,with carefully thickness setting models for precision.A set of high-precision thickness setting models are proposed to suit the production method.Because of frequent variations in rolling specification,a model structural for the combination of analytical models and statistical models is adopted to replace the traditional self-learning method.The deformation resistance and friction factor,the primary factors which affect model precision,are considered as the objectives of statistical modeling.Firstly,the coefficient fitting of deformation resistance analytical model based on over-determined equations set is adopted.Additionally,a support vector machine（SVM）is applied to the modeling of the deformation resistance and friction factor.The setting models are applied to a 1450 plate-coiling mill for titanium alloy plate rolling,and then thickness precision is found consistently to be within 3%,exceeding the precision of traditional setting models with a self-learning method based on a large number of stable rolling data.Excellent application performance is obtained.The proposed research provides a set of high-precision thickness setting models which are well adapted to the characteristics of titanium alloy plate cold rolling without tension.

Microstructural effects in corrosion of aluminium tube alloys

Fine gauge extruded aluminium alloy tubes can experience preferential corrosion and early failure when they are formed into ＂u-bend＂ via cold deformation. The relationship between the electrochemical reactivity and the microstructure of the bent vs straight parts of the tube was established. Investigations were carried out on two alloys containing 0.08% and 0.22% （mass fraction） of manganese. The corrosion morphology of bent tubes after immersion in salt water acetic acid test （SWAAT） solution showed the highest attack at the bent region of the high-Mn alloy. SEM characterisation of the alloys showed that each alloy has one main type of coarse intermetallic particle. However, TEM observation showed that there is a distinct difference in particle morphology between the bent and straight regions of the high-Mn tubes, the bent region revealed an additional population of 10 50 nm Mn-rich intermetallic particles, which increased both the anodic and cathodic reactivity. For the low-Mn alloy, no such effects were observed. The results suggested that cold deformation of the high-Mn tube allowed room temperature precipitation of fine Mn-rich particles, which increased the cathodic reactivity of that region by providing more cathodic sites, and increased the susceptibility to pitting by removing noble Mn from solid solution. Such an effect was not observed for the low-Mn alloy.

Study on WC dispersion-strengthened copper

Dispersion-strengthened copper (DSC) with WC as dispersoid was prepared bymeans of mechanical alloying (MA) following the traditional powder metallurgy (P/M) route. Influenceof WC content on the properties of material was discussed in detail, and result shows that when thevolume fraction of WC is 1.6%, the material achieves the best overall property, and a little moreparticle addition led to a less superior property owing to occurrence of particle agglomeration. Theas-sintered composite was designed to undergo a deformation of 75%. It is proved that appropriatedeformation is helpful to attain a higher density and consequently better properties. Deformedmaterial was then exposed to elevated temperature to test its effect on material. Annealing for 1 hat 1173K caused material to recover quite completely, but no obvious recrystallization was observed.It's supposed the particles handicaps motion of dislocations and material demonstrates goodretention of strength with substantial improvement in elongation.

Irregular Characteristics of Bond Interface Formation in Ultrasonic Wire Wedge Bonding

The mechanism of ultrasonic wire wedge bonding, one of the die/chip interconnection methods, was investigated based on the characteristics of the ultrasonic wire bonding joints. The Al-1%Si wire of 25 μm in diameter was bonded on Au/Ni/Cu pad and the joint cross-section was analyzed by scanning electron microscopy （SEM） and energy-dispersive X-ray spectroscopy （EDX）. The results indicated that it is irregular for the ultrasonic bond formation, non-welded at the centre but joining well at the periphery, especially at the heel and toe of the joint. Furthermore, the diffusion and/or reaction at the cross-section interface are not clear at C-zone, while there exists a strip layer microstructure at P-zone, and the composition is 78.96 at. pct Al and 14.88 at. pct Ni, close to the Al3Ni intermetallic compound. All these observations are tentatively ascribed to the plastic flow enhanced by ultrasonic vibration and repeated cold deformation driving interdiffusion between AI and Ni at bond interface.