Hot Deformation Behavior of a New Nuclear Use Reduced Activation Ferritic/Martensitic Steel

The hot deformation behavior and workability of a new reduced activation ferritic/martensitic steel named SIMP steel for accelerator-driven system were studied.The flow curve and its microstructure were studied at 900-1200℃ and strain rate range of 0.001-10 s~(-1).The results showed that the deformation behavior of the SIMP steel during hot compression could be manifested by the Zener-Hollomon parameter in an exponent-type equation.Based on the obtained constitutive equation,the calculated flow stresses were in agreement with the experimentally measured ones,and the average activity energies QDRV and QHW for the initiation of dynamic recrystallization and the peak strain were calculated to be 476.1 kJ/mol and 462.7 kJ/mol,respectively.Furthermore,based on the processing maps and microstructure evolution,the optimum processing condition for the SIMP steel was determined to be 1050-1200 ℃/0.001-0.1 s~(-1).     

Recent Research on the Deformation Behavior of Particle Reinforced Magnesium Matrix Composite: A Review

Particle reinforced magnesium matrix composite(PMMC) possesses the merits of high specific strength, high specific modulus, better dimensional stability, good wear resistance and lower production cost, which is thought as a promising material in the field of aerospace, automobile, electronic communication, etc. To eliminate the casting defect, the PMMC is usually experienced hot deformation process. The present paper mainly focuses on the deformation behavior of PMMCs. First, the development of PMMCs based on particle size is introduced. Then, the hot deformation technology and deformation mechanism of PMMCs at elevated temperature are given and analyzed, respectively. After reviewing the dynamic recrystallization and texture of PMMCs, its future development is suggested based on the current research progress.     

Imparting strength into nanofiberous yarn by adhesive bonding

Low strength is one of the main disadvantages of nanofibrous structures in some applications such as suture yarns. To overcome this matter, in the present research, a novel method was applied to improve the tensile properties of nanofiber yarns. For this purpose, nanofibers and particles of polyvinyl acetate (PVAc) were added as a hot melt adhesive to nanofiber yarns in order to initiate adhesive bonding between nanofibers by two approaches. In the first one, Nylon 66/ PVAc hybrid nanofiber yarn was produced in opposite charged nozzles set up. In another approach, PVAc particles were electrosprayed through one of the nozzles while nylon 66 nanofibers were producing through another one. Afterward, thermal treatment was carried out for 78 seconds on samples in different temperatures. The results indicate that tensile strength was improved up to 1.97 and 1.7 times in comparison to nylon 66 nanofiberous yarn by adding PVAc nanofibers and particles, respectively. FTIR analysis was also carried out to assess the hybrid sample composition after heat treatment.     

Integration of Adaptive Neuro Fuzzy Inference Systems and principal component analysis for the control of tertiary scale formation on tinplate at a hot mill

Scale is highly detrimental to surface quality for tinplate products. There are a large number of process variables at a typical hot mill and principal component analysis is a well-known technique for reducing the number of process variables. This paper estimates the principal components associated with the hot mill process variables and puts these through an Adaptive Neuro Fuzzy Inference System (ANFIS) to find those hot mill running conditions that will minimise the amount of scale observed on the bottom of the rolled strip. It was found that the variation observed in all the hot mill process variables could be captured through the use of just six principal components, and that using just three of these in an ANFIS was sufficient to identify those operating conditions leading to coils being produced with a consistently low scale count. Specifically, it was found that the best operating conditions for the hot mill were when the first component was lower than −0.098 the second lower than 0.8058 and the third higher than −0.482. These ranges in turn corresponded to certain hot mill temperatures that depended to some extent on the base chemistry of the incoming slab.     

Effects of temperature and strain rate on microstructure and mechanical properties of high chromium cast iron/low carbon steel bimetal prepared by hot diffusion-compression bonding

The objective of this study is to develop a hot diffusion-compression bonding process for cladding low carbon steel (LCS) to high chromium cast iron (HCCI) in solid-state. The influence of temperature (950–1150 °C) and strain rate (0.001–1 s⁻¹) on microstructure, hardness and bond strength of the HCCI/LCS bimetal were investigated. The interface microstructure reveals that the unbonded region can only be found for 950 °C due to lack of diffusion, while the intergrowth between the constituent metals occurred at and above 1100 °C. When bonding temperature increases to 1150 °C, a carbide-free zone was observed near the interface on the HCCI layer, and the thickness of the zone decreases with an increase of bonding strain rate. These evolutions indicate that the bond quality was improved by raising temperature and reducing strain rate due to the increase of element diffusion. The hot compression process of the bonding treatment not only changes the carbide orientation of the HCCI, but also increases the volume fraction of Cr–carbide. Based on the microstructural examinations and mechanical tests, the optimum bonding temperature and bonding strain rate are determined to be 1150 °C and 0.001 s⁻¹, respectively.     

A new method for manufacturing graded refractories by localized hot uniaxial pressing

In this study, a cylinder of fine-grained carbon-bonded alumina was pressed uniaxially at high temperatures in an argon atmosphere. The resulting changes in mechanical properties, physical properties and microstructure were described with various techniques. The porosity of the material was found to have decreased significantly, leading to higher density, higher dynamic Young's modulus, higher strength and increased hardness. Additionally, gradients in porosity and hardness were observed that resulted from inhomogeneous temperature distribution during compression. Possibilities and conditions for the production of graded refractory materials can be deduced from the results.     

Reanalysis of offshore T-joint fatigue life predictions based on a complete weld profile model

A comparison between the fatigue life predictions obtained by the stress concentration factors (SCFs) of 3D solid finite element (FE) models considering the weldment and the existing SCF parametric equations for tubular T-joints, is presented in this paper. From the study carried out, it was concluded that the existing parametric equations for predicting hot spot SCFs are very conservative and insufficient to be used for optimisation. SCFs should be carried out by modelling 3D solid joints which include the weldment and should be based on notch stresses measured on the external surface at the weld toe. The Offshore and Marine Renewable Energy industry could significantly reduce their investment costs using contemporary FE models, since slight overestimations of the SCF results in a corresponding large reduction in predicted service life.     

Influence of sintering pressure on the microstructure and tribological properties of low temperature fast sintered hot-pressed Y-TZP

Contrarily to conventional sintering (CS) method where longer cycles and high temperature (1400–1500?°C) are applied to sinter yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics, this work presents a faster and low temperature (1175?°C) way through hot pressing (HP) to produce full densified zirconia with good mechanical and tribological properties. This work is concerned with the influence of sintering pressure on the microstructure and tribological properties of hot-pressed Y-TZP. For this purpose, four sintering pressures 5, 20, 60 and 100?MPa were tested. The wear tests were carried out by reciprocating ball-on-plate as a simplified test for tooth-to-restorative material contact under 37?°C using artificial saliva to mimic oral conditions. The results demonstrated that density, hardness and tribological properties are strongly influenced by the sintering pressure, namely an improvement with pressure increase was achieved. The highest density, hardness values and wear resistance were achieved for Y-TZP samples produced at P?=?100?MPa. Furthermore, it was revealed that a smaller grain size for Z100 samples (full densification condition) was achieved comparatively to conventional-sintered Y-TZP. This work proves that it is possible to produce dense Y-TZP materials under low sintering temperature and faster cycles with reduced grain size without compromise mechanical and tribological properties.     

Corrosion behavior and magnetocaloric effect of FeNi(1J85) coated LaFe_(11.6)Si_(1.4)/Sn composites

The FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites were prepared by hot pressing(HP). The microstructure,corrosion behavior and magnetocaloric effect(MCE) of FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites were investigated systematically. The results show that the corrosion resistance of FeNi coated LaFe_(11.6)Si_(1.4)Sn composites is better than that of LaFe_(11.6)Si_(1.4)/Sn composites in deionized water. The maximum magnetic entropy change((-△S_M)~(max)) and relative cooling power(RCP) of FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites are 13.30 J/(kg-K) and 146.25 J/kg, respectively, which are larger than that((-△S_M)~(max), 10.65 J/(kg·K) and RCP, 106.53 J/kg) of LaFe_(11.6)Si_(1.4)/Sn composites in a low magnetic field change of 2 T. FeNi coated LaFe_(11.6)Si_(1.4)/Sn composites possess a more negative slope. The improvement of magnetic properties is due to high permeability FeNi permalloy(1 J85) which improves the itinerant-electron metamagnetic(IEM) transition. So, the method of coating FeNi can provide a new idea for enhancing the corrosion resistance and magnetocaloric effect of La(Fe_xSi_(1-x))_(13)-based materials.     

Experimental investigation of aerodynamic effects of probe on heat transfer from hot-wire sensors at vertical and horizontal orientations

Aerodynamic effects due to hot-wire anemometer (HWA) probe directly influence heat transfer from the probe sensor and result in reduced accuracy in two-dimensional measurements. This experimental research investigates the aerodynamic effects for hot-wire sensors through the study of some important factors such as probe geometry, flow scheme (velocity and direction) and orientation of the probe relative to the flow direction. In addition, flow velocity field between the prongs of a 10:1 model of a single normal probe is explored at different velocities and yaw angles, both at vertical and horizontal orientations of the probe. Results indicate that in vertical orientation, heat transfer from the sensors is always higher than horizontal orientation. Moreover, the aerodynamic effects cause a velocity increase of up to 6% in the vicinity of the sensor. In addition, the presence of the sensor in the flow, generates low-velocity field in the flow wake and a minor rotation of the flow in the vicinity of the sensor, which result in reduced heat transfer from the sensor in horizontal orientation compared to the vertical orientation.