Ultrahigh strength and improved electrical conductivity in an aging strengthened copper alloy processed by combination of equal channel angular pressing and thermomechanical treatment

In this paper,equal channel angular pressing and thermomechanical treatment was employed to improve the strength and electrical conductivity of an aging strengthened Cu-Ti-Cr-Mg alloy,and the microstructure and properties of the alloy were investigated in detail.The results showed that the samples deformed by the combination of cryogenic equal channel angular pressing(ECAP)and rolling had good comprehensive properties after aging at 400℃.The tensile strength of the peak-aged and over-aged samples was 1120 MPa and 940 MPa,with their corresponding electrical conductivity of 14.7%IACS and 22.1%IACS,respectively.ECAP and cryogenic rolling introduced high density dislocations,leading to the inhibition of the softening effects and refinement of the grains.After a long time aging at 400℃,the alloy exhibited ultra-high strength with obvious increasing electrical conductivity.The high strength was attributed to the synergistic effect of work hardening,grain refinement strengthening and precipitation strengthening.The precipitation of a large amount of Ti atoms from the matrix led to the high electrical conductivity of the over-aged sample.

Electrospinning-hot pressing technique for the fabrication of thermal and electrical storage membranes and its applications

The combination of electrospinning and hot pressing,namely the electrospinning-hot pressing technique(EHPT),is an efficient and convenient method for preparing nanofibrous composite materials with good energy storage performance.The emerging composite membrane prepared by EHPT,which exhibits the advantages of large surface area,controllable morphology,and compact structure,has attracted immense attention.In this paper,the conduction mechanism of composite membranes in thermal and electrical energy storage and the performance enhancement method based on the fabrication process of EHPT are systematically discussed.Moreover,the state-of-the-art applications of composite membranes in these two fields are introduced.In particular,in the field of thermal energy storage,EHPT-prepared membranes have longitudinal and transverse nanofibers,which generate unique thermal conductivity pathways;also,these nanofibers offer enough space for the filling of functional materials.Moreover,EHPT-prepared membranes are beneficial in thermal management systems,building energy conservation,and electrical energy storage,e.g.,improving the electrochemical properties of the separators as well as their mechanical and thermal stability.The application of electrospinning-hot pressing membranes on capacitors,lithium-ion batteries(LIBs),fuel cells,sodium-ion batteries(SIBs),and hydrogen bromine flow batteries(HBFBs)still requires examination.In the future,EHPT is expected to make the field more exciting through its own technological breakthroughs or be combined with other technologies to produce intelligent materials.

CLINICAL OBSERVATION ON TREATMENT OF PSEUDOBULBAR PARALYSIS-INDUCED DYSPHAGIA WITH OTOPOINT-PELLET-PRESSING PLUS ACUPUNCTURE

In the present paper, the therapeutic effects of otopoint pellet pressing plus body acupuncture and simple body acupuncture for dysphagia and water drinking induced coughing are compared in 126 cases of pseudobulbar paralysis who are randomly divided into treatment group (n=63) and control group (n=63). Main acupoints used are Shuigou (GV 26), Fengchi (GB 20), Lianquan (CV 23) and Sanyinjiao (SP 6), while otopoints used are Xin (MA IC), Gan (MA SC 5), Pi (MA IC), Shen (MA SC), Yanhou (MA T 3) and She (MA L). Following one course of treatment (12 sessions), in treatment group, of the 63 cases, 34 (54.0%) are cured, 18 (28.5%) have remarkable improvement, 5 (8.0%) have improvement, and 6 ( 9.0%) have no apparent changes, with the tottal effective rate being 90.5%; while in control group, of the 63 cases, 18 (28.5%) are cured, 11 (17.5%) have marked amelioration, 15 ( 24.0%) experience apparent amelioration and 19 (30.0%) have no obvious changes, with a total effective rate of 70.0%. The therapeutic effect of otopoint pellet pressing plus body acupuncture is significantly superior to that of simple body acupuncture in the treatment of dysphagia and water drinking induced coughing.

Effect of the capsule on deformation and densification behavior of nickel-based superalloy compact during hot isostatic pressing

The Shima yield criterion used in finite element analysis for nickel-based superalloy powder compact during hot isostatic pressing(HIP) was modified through uniaxial compression experiments. The influence of cylindrical capsule characteristics on FGH4096M superalloy powder compact deformation and densification behavior during HIP was investigated through simulations and experiments. Results revealed the simulation shrinkage prediction fitted well with the experimental shrinkage including a maximum shrinkage error of 1.5%. It was shown that the axial shrinkage was 1.7% higher than radial shrinkage for a cylindrical capsule with the size of ∮50 mm × 100 mm due to the force arm difference along the axial and radial direction of the capsule. The stress deviated from the isostatic state in the capsule led to the uneven shrinkage and non-uniform densification of the powder compact. The ratio of the maximum radial displacement to axial displacement increased from0.47 to 0.75 with the capsule thickness increasing from 2 to 4 mm. The pressure transmission is related to the capsule thickness, the capsule material performance, and physical parameters in the HIP process.

Effects of microstructure characteristics on the tensile properties and fracture toughness of TA15 alloy fabricated by hot isostatic pressing

Powder hot isostatic pressing(HIP) is an effective method to achieve near-net-shape manufacturing of high-quality complex thinwalled titanium alloy parts, and it has received extensive attention in recent years. However, there are few reports about the microstructure characteristics on the strengthening and toughening mechanisms of powder hot isostatic pressed(HIPed) titanium alloys. Therefore, TA15powder was prepared into alloy by HIP approach, which was used to explore the microstructure characteristics at different HIP temperatures and the corresponding tensile properties and fracture toughness. Results show that the fabricated alloy has a “basket-like structure” when the HIP temperature is below 950℃, consisting of lath clusters and surrounding small equiaxed grains belts. When the HIP temperature is higher than 950℃, the microstructure gradually transforms into the Widmanstatten structure, accompanied by a significant increase in grain size. The tensile strength and elongation are reduced from 948 MPa and 17.3% for the 910℃ specimen to 861 MPa and 10% for the 970℃ specimen.The corresponding tensile fracture mode changes from transcrystalline plastic fracture to mixed fracture including intercrystalline cleavage.The fracture toughness of the specimens increases from 82.64 MPa·m^(1/2)for the 910℃ specimen to 140.18 MPa·m^(1/2)for the 970℃ specimen.Specimens below 950℃ tend to form holes due to the prior particle boundaries(PPBs), which is not conducive to toughening. Specimens above 950℃ have high fracture toughness due to the crack deflection, crack branching, and shear plastic deformation of the Widmanstatten structure. This study provides a valid reference for the development of powder HIPed titanium alloy.

Effect of hot isostatic pressing processing parameters on microstructure and properties of Ti60 high temperature titanium alloy

Hot isostatic pressing parameters are critical to Ti60 high temperature titanium alloy castings which have wide application perspective in aerospace.In order to obtain optimal processing parameters,the effects of hot isostatic pressing parameters on defects,composition uniformity,microstructure and mechanical properties of Ti60 cast high temperature titanium alloy were investigated in detail.Results show that increasing temperature and pressure of hot isostatic pressing can reduce defects,especially,the internal defects are substantially eliminated when the temperature exceeds 920℃or the pressure exceeds 125 MPa.The higher temperature and pressure can improve the microstructure uniformity.Besides,the higher pressure can promote the composition uniformity.With the temperature increases from 880℃to 960℃,α-laths are coarsened.But with increasing pressure,the grain size of prior-βphase,the widths ofα-laths andα-colony are reduced.The tensile strength of Ti60 alloy is 949 MPa,yield strength is 827 MPa,and the elongation is 11%when the hot isostatic pressing parameters are 960℃/125 MPa/2 h,which exhibits the best match between the strength and plasticity.

Simple shear extrusion versus equal channel angular pressing:A comparative study on the microstructure and mechanical properties of an Mg alloy

Two severe plastic deformation(SPD)techniques of simple shear extrusion(SSE)and equal channel angular pressing(ECAP)were employed to process an extruded Mg-6Gd-3Y-1.5Ag(wt%)alloy at 553 K for 1,2,4 and 6 passes.The microstructural evolutions were studied by electron back scattered diffraction(EBSD)analysis and transmission electron microscopy(TEM).The initial grain size of 7.5μm in the extruded alloy was reduced to about 1.3μm after 6 SPD passes.Discontinuous dynamic recrystallization was suggested to be operative in both SSE and ECAP,with also a potential contribution of continuous dynamic recrystallization at the early stages of deformation.The difference in the shear strain paths of the two SPD techniques caused different progression rate of dynamic recrystallization(DRX),so that the alloys processed by ECAP exhibited higher fractions of recrystallization and high angle grain boundaries(HAGBs).It was revealed that crystallographic texture was also significantly influenced by the difference in the strain paths of the two SPD methods,where dissimilar basal plane texture components were obtained.The compression tests,performed along extrusion direction(ED),indicated that the compressive yield stress(CYS)and ultimate compressive strength(UCS)of the alloys after both SEE and ECAP augmented continuously by increasing the number of passes.ECAP-processed alloys had lower values of CYS and UCS compared to their counterparts processed by SSE.This difference in the mechanical responses was attributed to the different configurations of basal planes with respect to the loading direction(ED)of each SPD technique.

Superplastic behavior of a fine-grained Mg-Gd-Y-Ag alloy processed by equal channel angular pressing

An extruded Mg-6Gd-3Y-1.5Ag(wt%) alloy was processed by 6 passes of equal channel angular pressing(ECAP) at 553 K using route Bc to refine the microstructure. Electron back-scattered diffraction(EBSD) analysis showed a fully recrystallized microstructure for the extruded alloy with a mean grain size of 8.6 μm. The microstructure of the ECAP-processed alloy was uniformly refined through dynamic recrystallization(DRX). This microstructure contained fine grains with an average size of 1.3 μm, a high fraction of high angle grain boundaries(HAGBs), and nano-sized Mg_(5)Gd-type particles at the boundaries of the DRXed grains, detected by transmission electron microscopy(TEM). High-temperature shear punch testing(SPT) was used to evaluate the superplastic behavior of both the extruded and ECAP-processed alloys by measuring the strain rate sensitivity(SRS) index(m-value). While the highest m-value for the extruded alloy was measured to be 0.24 at 673 K, the ECAP-processed alloy exhibited much higher m-values of 0.41 and 0.52 at 598 and 623 K, respectively,delineating the occurrence of superplastic flow. Based on the calculated average activation energy of 118 kJ mol^(-1) and m-values close to 0.5, the deformation mechanism for superplastic flow at the temperatures of 598 and 623 K for the ECAP-processed alloys was recognized to be grain boundary sliding(GBS) assisted by grain boundary diffusion.

IPS e.max Press铸瓷与合金嵌体治疗后牙牙体缺损效果对比研究

目的探讨IPS e.max Press铸瓷与合金嵌体治疗后牙牙体缺损的效果。方法前瞻性纳入2020-05—2022-05三门峡市中心医院口腔科收治的后牙牙体缺损患者,根据修复材料分为IPS e.max Press铸瓷嵌体组(铸瓷组)和合金嵌体组(合金组)。比较2组患者的基线资料。治疗前后检测患者的龈沟液中炎性因子、评价牙周健康情况。治疗3个月后评价牙体缺损边缘密合度和美牙效果。结果共纳入86例(132颗牙)患者,每组43例(66颗牙)。2组患者的基线资料差异无统计学意义(P>0.05)。治疗后铸瓷组患者的IL-6、IL-8、CXCL16水平和GI、SBI及PLI评分均低于合金组;牙体缺损边缘密合度优于合金组,美牙效果满意率高于合金组。差异均有统计学意义(P<0.05)。结论与合金嵌体比较,采用IPS e.max Press铸瓷嵌体治疗后牙牙体缺损有利于降低龈沟液中炎性因子水平,改善牙周健康状况和牙体缺损边缘密合度,并可提高患者对美牙效果的满意度。但仍需进行更大样本量的前瞻性随机对照研究予以证实。

Preparation of Al-doped ZnO sputter target by hot pressing

Al-doped ZnO （AZO） target was prepared by hot pressing using ZnO and Al2O3 powder in mass ratio of 98：2.The effects of hot pressing conditions including temperature,pressure and preserving time on relative density were investigated.Pore evolution and phase structure change during densification process were studied.The results show that AZO target with super high relative density of 99% was prepared by two-stage hot pressing method under pressure of 35MPa,temperature of 1 050℃ and 1 150℃ with preserving time of 1 h,respectively.At temperature around 1 050℃,the number of isolated pore wasminimum.At temperature lower than 900℃,there existed Al2O3 phase.At temperature higher than 1 000℃,ZnAl2O4 phase was generated and its content was increased with temperature increasing.Hot pressing method had the advantage over pressureless sintering that the content of ZnAl2O4 was lower and sintering temperature could be also lower.With increasing the hot pressing temperature and preserving time,the electric resistivity of AZO target decreased greatly.A low resistivity of 3 10-3 cm was achieved under the temperature of 1 100℃,pressure of 35MPa and preserving time of 10 h.

Microstructure and mechanical properties of Mg-Gd-Y-Zr alloy processed by equal channel angular pressing

Microstructure evolution and texture development and their effects on mechanical properties of a Mg-Gd-Y-Zr alloy during equal channel angular pressing（ECAP） were investigated.It is found that the microstructure is still inhomogeneous after four passes,and two zones,namely the fine grain zone（FGZ） and the coarse grain zone（CGZ） are formed.The grain refinement occurs mainly by particle-stimulated nucleation（PSN） mechanism,which led to a more random texture after four passes of ECAP.In the ECAP-processed alloy,the strength did not increase while the ductility was enhanced dramatically compared with the as-received condition.The change of ductility of this alloy was discussed in terms of texture and second phase particles.

Effect of equal-channel angular pressing and aging on corrosion behavior of ZK60 Mg alloy

Commercial ZK60 Mg alloy was processed by multi-pass equal-channel angular pressing（ECAP） and subsequent aging to investigate the effect of grain refinement and second-phase redistribution on its corrosion behavior. Electrochemical tests show that the fine-grained samples after more ECAP passes have higher corrosion current densities（Jcorr） in the polarization curves, lower charge-transfer resistance（Rt） values in the EIS plots. The severe plastic deformation decreases the alloy corrosion resistance besides the well-known strengthening and toughening. Scanning Kelvin probe（SKP） measurement shows that the anodic and cathode sites are homogeneously distributed on the surface of the fine-grained alloy, which inhibits localized corrosion. The SKP potential, having linear relationship with the corrosion potential（φcorr）, decreases with increasing the ECAP pass. Furthermore, the post-ECAP aging can slightly improve the corrosion resistance of the fine-grained ZK60 Mg alloy and enhance the comprehensive performances, due to the stress relief and uniform distribution of second-phase particles.

Influence of twist extrusion process on consolidation of pure aluminum powder in tubes by equal channel angular pressing and torsion

In comparison with the conventional equal channel angular pressing（ECAP） process,a comprehensive study of influence of twist extrusion（TE） process on consolidating pure aluminum powder in tubes（PITs） by equal channel angular pressing and torsion（ECAPT） was conducted via three-dimensional（3D） finite element simulation,experimental investigation and theoretical analysis.Simulation results revealed that during the consolidation of aluminum powder particles by ECAPT,TE process played a significant role of back pressure.Due to the torsional shear and high hydrostatic pressure exerted by twist channel,both the magnitude and homogeneity of the effective strain were increased markedly.After one pass of ECAPT process using a square channel with an inner angle of 90° and a twist slope angle of 36.5° at 200℃,commercial pure aluminum powder particles were successfully consolidated to nearly full density.Simulation and experimental results showed good agreement.In the microstructure observations,grains were greatly refined.At the same time,porosities were effectively eliminated by shrinking in size and breaking into small ones.Microhardness test indicated that strain distribution of ECAPT-processed billet was more homogeneous with respect to the ECAP-processed one.All these improvements may be attributed to the extreme intense shear strain induced during ECAPT and the increase in self-diffusion coefficient of aluminum due to the back pressure exerted by TE process.

Hot pressing densification of WC-Mo_xC binderless carbide

WC-6MoxC-0.47Cr3C2-0.28VC binderless carbide was prepared by hot pressing （1700 °C, 20 MPa）. The sample was observed and analyzed by scanning electron microscopy, energy dispersive X–ray spectroscopy and X–ray diffraction. The results show that during the hot pressing process, W atoms dissolve substantially into the MoxC crystal lattices; whilst, the reverse dissolution of Mo atoms into the WC crystal lattices takes place. Consequently, the main phase and binder phase structure are formed. The phase compositions of the main phase and binder phase are a WC-based solid solution containing Mo and a Mo2C-based solid solution containing W, respectively. The isotropic dissolution and precipitation of W and Mo atoms do not result in substantial carbide coarsening. The mechanism for the densification was discussed.

IPS e.max press热压铸造陶瓷全冠及二氧化锆全瓷冠对前牙修复患者牙龈健康美观度的影响

目的:比较IPS e.max press热压铸造陶瓷全冠及二氧化锆全瓷冠对前牙修复患者牙龈健康、美观度的影响,为前牙美学修复的材料选择提供临床参考。方法:以2021年5月至2022年5月于我院接受前牙修复的104例患者为研究对象,以随机数字表法分为两组,分别52例。观察组、对照组分别以IPS e.max press铸瓷全冠、二氧化锆全瓷冠修复,比较两组患者的临床修复效果及修复后的牙龈指数、菌斑指数、龈沟出血指数、龈沟液炎性因子水平。结果:观察组边缘密合度、继发龋情况均优于对照组(P<0.05);修复后,观察组牙龈指数、菌斑指数等显著小于对照组,龈沟液IL-6、IL-8及TNF-α水平显著低于对照组(P<0.05);修复12个月后,观察组PES评分高于对照组(P<0.05)。结论:相比于二氧化锆全瓷冠,IPS e.max press铸瓷全冠具有良好的前牙美学修复效果,可降低龈沟液炎性因子水平,改善牙龈健康,并能提高前牙美观度。

Production of carbon anodes by high-temperature mould pressing

Laboratory-scale carbon anodes were produced by a new method of high temperature mould pressing, and their physico-chemical properties were studied. The influence of mould pressing conditions and coal pitch addition on the bulk density, crushing strength, and oxidation resistance was analyzed. The mierostructure of carbon anodes was investigated by scanning electron microscopy （SEM）, and the mechanism of producing carbon anodes by high-temperature mould pressing was analyzed. The results show that when the anodes are produced by high-temperature mould pressing, coal pitch can expand into the coke particles and fill the pores inside the particles, which is beneficial for improving the quality of prebaked anodes. The bulk density of carbon anodes is 1.64-1.66 g/cm3, which is 0.08-0.12 g/cm3 higher than that of industrial anodes, and the oxidation resistance of carbon anodes is also significantly improved.

Uniaxial compressive behavior of equal channel angular pressing Al at wide temperature and strain rate range

Uniaxial compressive experiments of ultrafine-grained Al fabricated by equal channel angular pressing(ECAP) method were performed at wide temperature and strain rate range. The influence of temperature on flow stress, strain hardening rate and strain rate sensitivity was investigated experimentally. The results show that both the effect of temperature on flow stress and its strain rate sensitivity of ECAPed Al is much larger than those of the coarse-grained Al. The temperature sensitivity of ultrafine-grained Al is comparatively weaker than that of the coarse-grained Al. Based on the experimental results, the apparent activation volume was estimated at different temperatures and strain rates. The forest dislocation interactions is the dominant thermally activated mechanism for ECAPed Al compressed at quasi-static strain rates, while the viscous drag plays an important role at high strain rates.

Effect of consolidation parameters on mechanical properties of Cu-based bulk amorphous alloy consolidated by hot pressing

Cu50Zr40Ti10 bulk amorphous alloys were fabricated by hot pressing gas-atomized Cu50Zr40Ti10 amorphous powder under different consolidation conditions without vacuum and inert gas protection. The consolidation conditions of the Cu50Zr40Ti10 amorphous powder were investigated based on an L9（34） orthogonal design. The compression strength and strain limit of the Cu50Zr40Ti10 bulk amorphous alloys can reach up to 1090.4 MPa and 11.9 %, respectively. The consolidation pressure significantly influences the strain limit and compression strength of the compact. But the mechanical properties are not significantly influenced by the consolidation temperature. In addition, the preforming pressure significantly influences not the compression strength but the strain limit. The optimum consolidation condition for the Cu50Zr40Ti10 amorphous powder is first precompacted under the pressure of 150 MPa, and then consolidated under the pressure of 450 MPa and the temperature of 380 °C.

Refinement and consolidation of pure Al particles by equal channel angular pressing and torsion

Consolidation of pure Alpowder was conducted at 200 ℃ by equal channel angular pressing and torsion （ECAPT） method. The grain refinement and consolidation behavior were deeply investigated by scan electronic microscopy （SEM） and transmission electronic microscopy （TEM）. The density, hardness and room temperature compression properties of the deformed samples were measured. The experiment results show that ECAPT is an effective method of consolidating powders at relatively low temperatures. Pure A1 particles are successfully consolidated into dense bulk material after 4 passes of ECAPT at 200 ℃. The consolidated material possesses fine grain structure and excellent mechanical properties. The refinement and consolidation mechanisms were analyzed. ECAPT is a promising method to produce the high-performance bulk materials from particles.

Plastic forming simulations of cold isostatic pressing of selective laser sintered components

A combined method of selective laser sintering （SLS） and cold isostatic pressing （CIP） was applied to manufacturing metal parts rapidly. Finite element method was used to predict final dimensions and decrease cost. The simulations of CIP of selective laser sintered parts were carried out by Drucker-Prager-Cap constitutive model with ABAQUS computer program. The property of metal powder was measured by CIP experiments. The results show the rubber bag and the friction coefficient have little influence on results of simulations. The parts only have uniform shrinkage and have no obvious distortion in shape. The results of simulations show a good agreement with the experimental results and the calculated results, indicating that the Drucker-Prager-Cap model is an effective model to simulate CIP process. The simulations could give a useful direction to forming process of the CIP of selective laser sintered components. K