Explore the vast range of titles available.

Tensile tests of GH4169 alloy were performed at room temperature. Different fractions, distributions and shapes of δ phase was prepared by aging treated at 880 °C, 930 °C and 980 °C for 5 h or 10 h. The effect of δ phase on the mechanical properties of GH4169 alloy was investigated. The results show that 0.2% yield strength and ultimate tensile strength of GH4169 alloy increase by 61 MPa and 78 MPa respectively when the fraction of δ phase increases from 2.20% to 5.21%. Then, the ultimate tensile strength remains at 1 012 MPa even when the fraction of δ phase reaches 7.56%. The fraction effect of δ phase on the strength improvement of GH4169 alloy is more significant than morphology, and the critical fraction value is 5.21%. In addition, the elongation decreases by 14.1% when the fraction of δ phase increases from 2.20% to 7.56%. Excessive needle or short rod shaped δ phase is responsible for the reduction of elongation.

A neural network with feed-forward topology and back propagation algorithm was used to predict the effects of chemical composition and tensile test parameters on hardness of heat affected zone （HAZ） in X70 pipeline steels. The mass percent of chemical compositions （i. e. carbon equivalent based upon the International Institute of Welding equation （CEIIw）, the carbon equivalent based upon the chemical portion of the ho-Bessyo carbon equivalent equation （CEecm）, the sum of the niobium, vanadium and titanium concentrations （CvTaNb）, the sum of the niobium and vanadium concentrations （CNbv）, the sum of the chromium, molybdenum, nickel and copper concentrations （CcrMoNiCu））, yield strength （YS） at 0. 005 offset, ultimate tensile strength （UTS） and percent elongation （El） were considered as input parameters to the network, while Vickers microhardness with 10 N load was considered as its output. For the purpose of constructing this model, 104 different data were gathered from the experimental re- sul.ts. Scatter diagrams and two statistical criteria, i.e. absolute fraction of variance （R2 ） and mean relative error （MRE）, were used to evaluate the prediction performance of the developed model. The developed model can be fur- ther used in practical applications of alloy and thermo-mechanical schedule design in manufacturing process of pipe line steels.

The deformation characteristics of tailor rolled blank （TRB） in the course of uniaxial tension were studied by means of analysis, test and simulation. The mechanical analytical model of TRB during uniaxial tension was set up, and the deformation formulae for the thinner side and for the thicker side were derived to quantify the deformation of TRB. On this basis, uniaxial tension tests on TRB and ordinary blanks （the thinner side and the thicker side of TRB） were conducted. Lagrange polynomial interpolation method was adopted to construct the stress-strain fields of unannealed and annealed TRBs for solving TRB material parameters, and then, uniaxial tension simulation on TRB was completed. Deformations and properties of unannealed TRB were compared with those of annealed TRB, and the thinner side and the thicker side were also compared. Finally, the research results were explained by metallurgical structure. The results show that nonuniform deformation happens in TRB during uniaxial tension, and the necking occurs on the thinner side. The agreement of analysis, test and simulation confirms the correctness of the analytical model and the deformation formulae. The findings of this paper can lay the foundation for the future study on TRB stamping formability and provide a way for TRB modeling.

The Portevin-Le Chatelier （PLC） effect in the Nimonic 263 superalloy was investigated by tensile test at a wide temperature ranges from 293 to 1033 K and strain rates between 0.1 and 6.25 × 10^-6 s-1. Simple binary alloys Ni- 0.4C, Ni-24Cr and Ni-5（8）Mo were also tested in order to identify which elements were responsible for the PLC effect in the Nimonic 263 alloy. The results demonstrated that for Nimonic 263 alloy, PLC effect occurred at certain temperatures and low strain rates. Normal PLC effect exhibiting type-A and -（A ＋ B） serrations was attributed to the enhanced solute diffusion with increasing temperature, while inverse PLC effect with type-C serration was caused by unlocking process. The activation energy for the normal PLC effect was calculated to be 68 kJ/mol, and diffusion of substitutional solutes such as Cr and Mo was identified to be responsible for the PLC effect. In comparison with the PLC effect in simple binary alloys, solute atmospheres formed by different kinds of atoms in Nimonic 263 alloy work more effectively, increasing locking strength and corresponding mean stress drop magnitude.

The martensitic transformation behavior and mechanical properties of austenitic stainless steel 304 were studied by both experiments and numerical simulation. Room temperature tensile tests were carried out at various strain rates to investigate the effect on volume fraction of martensite, temperature increase and flow stress. The results show that with increasing strain rate, the local temperature increases, which suppresses the transformation of martensite. To take into account the dependence on strain level, strain rate sensitivity and thermal effects, a kinetic model of martensitic transformation was proposed and constitutive modeling on stress-strain response was conducted. The validity of the proposed model has been proved by comparisons between simulation results and experimental ones.

A series of monotonic uniaxial tensile tests, strain-controlled and stress-controlled cyclic tests of SA508-3 steel were conducted from 25 to 350℃. Results showed that the steel exhibited temperature-dependent cyclic softening characteristic and obvious ratcheting behavior, and dynamic strain aging was observed in the range of 250-350℃. Based on experimental observations, a temperature-dependent cyclic plastic constitutive model was proposed by introducing the nonlinear cyclic softening and kinematic hardening rules, and the dynamic strain aging was also considered into the constitutive model. Comparisons between experiments and simulations were carded out to validate the proposed model at elevated temperature.

To investigate the tensile deformation behavior of high strength anti-seismic steel with multi-phase microstructure, tensile tests with strains of 0.05, 0.12 and 0.22 were performed at room temperature. Microstructure of tested steels was observed by means of optical microscopy (OM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Tensile mechanical properties of tested steels were obtained, and the influence of bainite content on deformation behavior was also discussed. Meanwhile, the deformation mechanism of steel with three kinds of microstructures of bainite, pearlite and ferrite was analyzed. Results show that tested steel with high volume fraction of bainite exhibits a continuous deformation behavior, and this may be attributed to a higher bainite volume fraction and a lower mobile dislocation density. The morphology of microstructure will influence the mechanical properties of tested steels. An increasing content of bainite can improve the tensile strength, but reduce the plasticity and toughness of the tested steels. In the deformation process of 0.039Nb steel, the ferrite and bainite have priorities to deform, and the deformation exhibits co-deformation of all microstructures in the later stage of deformation. In the deformation process of 0.024Nb-0.032V steel, the ferrite and pearlite have priorities to deform, and the deformation exhibits co-deformation of all microstructures in the later stage of deformation.

Sheet metal formed of lightweight materials such as aluminum sheeting has received great attention related to the reduction of vehicle emissions. This paper evaluates the anisotropic yield locus using Kuwabara＇s biaxial tensile tester and stretches formability using Hecker＇s hemispheri- cal punch stretching test for aluminum 6016-T4 sheet material. The anisotropic yield locus of the A16016-T4 sheet measured is fitted well by the modified Drucker yield func- tion. Moreover the best fitting to the experimental stress- strain curve from the tensile test was obtained by taking an appropriate hardening model. Analytical study to predict the stretch formability by using Hora＇s Modified Maximum Force Criterion （MMFC） was performed. The predicted forming limit curves （FLC） based on various yield functions were compared with the experiments and discussed.

The effect of adding 0.5mass% Cu on ductility and magnetic properties of Fe-6.5Si（mass%）alloy was investigated.The alloys with and without 0.5mass% Cu addition were warm rolled into thin sheets of thickness no more than 0.3mm at temperature below 600 ℃.It was found that the alloy with 0.5mass% Cu addition was more easily warm rolled than Cu-free alloy.Tensile tests were carried out to further investigate this phenomenon,which confirmed that the ductility of the alloy with 0.5mass% Cu addition was significantly higher than that of Cu-free alloy at 550 ℃.Based on the results of transmission electron microscopy analysis,the ductility increase of the alloy with 0.5mass% Cu addition was attributed to the effect of Cu on the promotion of dynamic recovery and suppression of long-range order in the alloy during warm rolling process.It was also observed that the iron loss was lower and inductance was higher for the alloy with 0.5 mass% Cu addition.Thus,it can be concluded that adding a suitably small amount of Cu would not only increase the ductility of Fe-6.5Si alloy at warm rolling temperatures but also improve its magnetic properties.

Room temperature tensile tests of Fe-Mn-A1 C low density steels with four different chemical compositions were conducted to clarify the dominant deformation mechanisms. Parameters like product of strength and elongation, as well as specific strength and curves of stress-strain relations were calculated. The microstructures and tensile fracture morphologies were observed by optical microscope, scanning electron microscope and transmission electron mi-croscope. The tensile behavior of low density steel was correlated to the microstructural evolution during plastic de formation, and the effects of elements, cooling process and heat treatment temperature on the mechanical properties of the steels were analyzed. The results show that the tensile strength of steels with different cooling modes is more than 1000 MPa. The highest tensile strength of 28Mn-12Al alloy reached 1230 MPa, with corresponding specific strength of 189.16 MPa· cm^3·g^-1 , while the specific strength of 28Mn-10Al alloy was 178.98 MPa·cm^3·g^-1 , and the excellent product of strength and elongation of 28Mn-SAl alloy was over 69.2 GPa·%. A large number of ferrite reduced the ductility and strain hardening rate of the alloy, while the existence of κ carbides may improve the strength but weaken the plasticity. Some fine κ carbides appeared in the water-quenched specimen, while coarse carbides were observed in the air-cooled specimen. High temperature heat treatment improved the decomposition ki- netics of 7 phase and the diffusion rate of carbon, thus speeded up the precipitation of fine κ carbides. The dominant deformation mechanism of low density steel was planar glide, including shear-band-induced plasticity and microband- induced plasticity.