Combination of cataract surgery with intravitreal injection of dexamethasone intravitreal implant(Ozurdex)for uveitis-induced cataract

AIM:To evaluate the long-term results of patients with chronic uveitis-induced cataract by phacoemulsification with IOL implantation and intravitreal injection of dexamethasone(DEX)intravitreal implant(Ozurdex).METHODS:The study included 32 eyes of 26 patients treated with DEX implant due to chronic uveitis-induced cataract and followed up for at least a year.Best-corrected visual acuity(BCVA),intraocular pressure(IOP),anterior chamber reaction,central macular thickness(CMT),intraoperative and postoperative complications and uveitis recurrence were analyzed retrospectively.RESULTS:A successful surgery was performed in all patients.The average follow-up period was 12mo.The female/male ratio was 13/13.Mean age was 45.65±3.83y(range 26 to 65y).Etiologically,rheumatic arthritis occurred in 6 patients(18.75%),ankylosing spondylitis in 4(12.50%),HLA-B27 associated uveitis in 3(9.38%),Vogt-KoyanagiHarada-associated uveitis in 4(12.50%),Behcet’s disease in 2(6.25%),and 7(21.88%)suffered from unknown diseases.All 32 eyes had varying degrees of improvement at 12mo after surgery,with 2 eyes showing BCVA of 0.1 or below(6.25%),6 having 0.1-0.5(18.75%),18 of 0.5-1.0(56.25%),and 6 of 1.0 or above(18.75%).No cases with increased IOP were observed.The values of mean CMT was increased at day 1,decreased at 1,3mo after surgery and increased at 6,12mo after surgery.No severe uveitis reactions,such as fibrinous exudates in the anterior chamber and exudative membrane formation on the anterior surface of the IOL,were observed after surgery.CONCLUSION:The present studies show that intravitreal injection of Ozudex during cataract operation can provide a new option for the clinical treatment of uveitis-induced cataract.

Computational exploration of the significance of COPS6 in cancer:Functional and clinical relevance across tumor types

BACKGROUND The COP9 signalosome subunit 6(COPS6)has been implicated in cancer progression,while its precise role in most types of cancer remains elusive.AIM To investigate the functional and clinical relevance of COPS6 across various tumor types using publicly available databases.METHODS We used R software and online analysis databases to analyze the differential expression,prognosis,mutation and related functions of COPS6 in pan-cancer.RESULTS Differential expression analysis and survival analysis demonstrated that COPS6 was highly expressed and associated with high-risk profiles in the majority of cancer types.Possible associations between COPS6 expression level and prognostic outcomes were found using data from public databases.Mutational analysis revealed that missense mutations were the predominant type of COPS6 mutation.Additionally,positive correlations were identified between COPS6 expression level and tumor mutational burden and microsatellite instability in most types of cancer.Immune infiltration analysis demonstrated a negative correlation between COPS6 expression level and CD8+T cell infiltration in certain types of cancer.The correlation between COPS6 expression level and cancerassociated fibroblast infiltration exhibited heterogeneity,in which a positive correlation was found in head and neck squamous cell carcinoma and tenosynovial giant cell tumor,and a negative correlation was identified in diffuse large B-cell lymphoma and thymoma.The correlation between COPS6 expression level and macrophage infiltration was closely related to macrophage type.Gene co-expression and enrichment analysis highlighted transcription elongation factor B polypeptide 2 and G protein pathway suppressor 1 were significantly and positively associated with COPS6 expression level.These genes were predominantly involved in processes,such as ubiquitin-mediated proteolysis and human immunodeficiency virus 1 infection.CONCLUSION In conclusion,this study systematically explored the significance of COPS6 across different tumor types,providing a solid foundation for considering COPS6 as a novel biomarker in cancer research.

利用赝电容效应提高Se修饰MnO/Mn3O4复合负极材料的储锂容量及倍率性能

为了提高锰氧化物负极材料的倍率和循环性能,采用沉淀法及热处理法,通过调控Mn2O3与Se粉的反应温度,制备Mn O/Mn3O4/Se Ox(x=0,2)复合负极材料。Mn O/Mn3O4/Se Ox负极在3 A/g电流密度下经过560次充放电循环后放电比容量为1007 m A·h/g。循环伏安法定量分析结果表明,在2.0 m V/s的扫描速率下赝电容贡献率高达89.5%。研究结果表明,Mn O与Mn3O4之间存在明显的协同效应。

Analytical Compliance Modeling of Serial Flexure-Based Compliant Mechanism Under Arbitrary Applied Load

Analytical compliance model is vital to the flexure-based compliant mechanism in its mechanical design and motion control. The matrix is a common and effective approach in the compliance modeling while it is not well developed for the closed-loop serial and parallel compliant mechanisms and is not applicable to the situation when the external loads are applied on the flexure members. Concise and explicit analytical compliance models of the serial flexure-based compliant mechanisms under arbitrary loads are derived by using the matrix method. An equivalent method is proposed to deal with the situation when the external loads are applied on the flexure members. The external loads are transformed to concentrated forces applied on the rigid links, which satisfy the equations of static equilibrium and also guarantee that the deformations at the displacement output point remain unchanged. Then the matrix method can be still adopted for the compliance analysis of the compliant mechanism.Finally, several specific examples and an experimental testare given to verify the effectiveness of the compliance models and the force equivalent method. The research enriches the matrix method and provides concise analytical compliance models for the serial compliant mechanism.

Basal physiological parameters in domesticated tree shrews (Tupaia belangeri chinensis)

Establishing non-human primate models of human diseases is an efficient way to narrow the large gap between basic studies and translational medicine. Multifold advantages such as simplicity of breeding, low cost of feeding and facility of operating make the tree shrew an ideal non-human primate model proxy. Additional features like vulnerability to stress and spontaneous diabetic characteristics also indicate that the tree shrew could be a potential new animal model of human diseases. However, basal physiological indexes of tree shrew, especially those related to human disease, have not been systematically reported. Accordingly, we established important basal physiological indexes of domesticated tree shrews including several factors: (1) body weight, (2) core body temperature and rhythm, (3) diet metabolism, (4) locomotor rhythm, (5) electroencephalogram, (6) glycometabolism and (7) serum and urinary hormone level and urinary cortisol rhythm. We compared the physiological parameters of domesticated tree shrew with that of rats and macaques. Results showed that (a) the core body temperature of the tree shrew was 39.59±0.05 °C, which was higher than that of rats and macaques; (b) Compared with wild tree shrews, with two activity peaks, domesticated tree shrews had only one activity peak from 17:30 to 19:30; (c) Compared with rats, tree shrews had poor carbohydrate metabolism ability; and (d) Urinary cortisol rhythm indicated there were two peaks at 8:00 and 17:00 in domesticated tree shrews, which matched activity peaks in wild tree shrews. These results provided basal physiological indexes for domesticated tree shrews and laid an important foundation for diabetes and stress-related disease models established on tree shrews.

Association of colorectal cancer susceptibility variants with esophageal cancer in a Chinese population

AIM: To investigate the association between colorectal cancer(CRC) genetic susceptibility variants and esophageal cancer in a Chinese Han population.METHODS: A case-control study was conducted including 360 esophageal cancer patients and310 healthy controls. Thirty-one single-nucleotide polymorphisms(SNPs) associated with CRC risk from previous genome-wide association studies were analyzed. SNPs were genotyped using Sequenom Mass-ARRAY technology, and genotypic frequencies in controls were tested for departure from HardyWeinberg equilibrium using a Fisher's exact test. The allelic frequencies were compared between cases and controls using a χ 2 test. Associations between the SNPs and the risk of esophageal cancer were tested using various genetic models(codominant, dominant,recessive, overdominant, and additive). ORs and95%CIs were calculated by unconditional logistic regression with adjustments for age and sex.RESULTS: The minor alleles of rs1321311 and rs4444235 were associated with a 1.53-fold(95%CI:1.15-2.06; P = 0.004) and 1.28-fold(95%CI: 1.03-1.60;P = 0.028) increased risk of esophageal cancer in the allelic model analysis, respectively. In the genetic model analysis, the C/C genotype of rs3802842 was associated with a reduced risk of esophageal cancer in the codominant model(OR = 0.52, 95%CI:0.31-0.88; P = 0.033) and recessive model(OR =0.55, 95%CI: 0.34-0.87; P = 0.010). The rs4939827C/T-T/T genotype was associated with a 0.67-fold(95%CI: 0.46-0.98; P = 0.038) decreased esophageal cancer risk under the dominant model. In addition,rs6687758, rs1321311, and rs4444235 were associated with an increased risk. In particular, the T/T genotype of rs1321311 was associated with an 8.06-fold(95%CI: 1.96-33.07; P = 0.004) increased risk in the codominant model.CONCLUSION: These results provide evidence that known genetic variants associated with CRC risk confer risk for esophageal cancer, and may bring risk for other digestive system tumors.

Serological Diagnosis of Liver Metastasis in Patients with Breast Cancer

Objective To diagnose and explore the serological diagnostic factors for liver metastasis in patients with breast cancer before symptoms occur. Methods A total of 430 female in-patients with breast cancer of stages 0 to IIIC who came to Tianjin Medical University Cancer Institute and Hospital from January 2003 to January 2004 were studied and followed up until May 2011.Serum levels of biochemical markers for tumor and liver were measured at the time of diagnosis. Results Liver metastasis was more likely to occur in patients with stage III cancer or c-erbB-2-positive expression.Alanine aminotransferase,aspartate aminotransferase,γ-glutamyltransferase(GGT),alkaline phosphatase,lactate dehydrogenase(LDH),and carbohydrate antigen 153(CA153) levels were significantly higher in patients with liver metastasis than those without liver metastasis. Diagnostic indices of LDH,GGT,and CA153 were 174 U/L,32 U/L,and 26.48μg/L,respectively.The areas under the curves of LDH, GGT,and CEA were 0.795,0.784,and 0.661,respectively,and sensitivities of parallel tests for LDH and CA153 and for GGT and CA153 were 88.6%and 85.7%,respectively.The specificity of serial tests for both pairs of enzymes was 97.7%. Conclusions The sensitivity and specificity of combined tumor and biochemical markers could be used as indicators during screening for breast-liver metastasis.

Celastrol inhibits migration, proliferation and transforming growth factor-β2-induced epithelial-mesenchymal transition in lens epithelial cells

AIM: To investigate the mechanism of celastrol in inhibiting lens epithelial cells(LECs) fibrosis, which is the pathological basis of cataract.METHODS: Human LEC line SRA01/04 was treated with celastrol and transforming growth factor-β2(TGF-β2). Wound-healing assay, proliferation assay, flow cytometry, real-time polymerase chain reaction(PCR), Western blot and immunocytochemical staining were used to detect the pathological changes of celastrol on LECs. Then, we cultured Sprague-Dawley rat lens in medium as a semi-in vivo model to find the function of celastrol further.RESULTS: We found that celastrol inhibited the migration of LECs, as well as proliferation(P<0.05). In addition, it induced the G2/M phase arrest by cell cyclerelated proteins(P<0.01). Moreover, celastrol inhibited epithelial-mesenchymal transition(EMT) by the blockade of TGF-β/Smad and Jagged/Notch signaling pathways.CONCLUSION: Our study demonstrates that celastrol could inhibit TGF-β2-induced lens fibrosis and raises the possibility that celastrol could be a potential novel drug in prevention and treatment of fibrotic cataract.

Phase-Division-Based Dynamic Optimization of Linkages for Drawing Servo Presses

Existing linkage-optimization methods are designed for mechanical presses; few can be directly used for servo presses, so development of the servo press is limited. Based on the complementarity of linkage optimization and motion planning, a phase-division-based linkage-optimization model for a drawing servo press is established. Considering the motion-planning principles of a drawing servo press, and taking account of work rating and efficiency, the constraints of the optimization model are constructed. Linkage is optimized in two modes: use of either constant eccentric speed or constant slide speed in the work segments. The performances of optimized linkages are compared with those of a mature linkage SL4-2000A,which is optimized by a traditional method. The results show that the work rating of a drawing servo press equipped with linkages optimized by this new method improved and the root-mean-square torque of the servo motors is reduced by more than 10%. This research provides a promising method for designing energy-saving drawing servo presses with high work ratings.

Clinical outcomes with large macular holes using the tiled transplantation internal limiting membrane pedicle flap technique

AIM: To report the surgical technique and efficacy of the tiled transplantation internal limiting membrane(ILM) pedicle flap technique after vitrectomy for 33 patients with large macular hole(MH).

Transmission Index Research of Parallel Manipulators Based on Matrix Orthogonal Degree

Performance index is the standard of performance evaluation, and is the foundation of both performance analysis and optimal design for the parallel manipulator. Seeking the suitable kinematic indices is always an important and challenging issue for the parallel manipulator. So far, there are extensive studies in this field,but few existing indices can meet all the requirements, such as simple, intuitive, and universal. To solve this problem,the matrix orthogonal degree is adopted, and generalized transmission indices that can evaluate motion/force transmissibility of fully parallel manipulators are proposed.Transmission performance analysis of typical branches,end effectors, and parallel manipulators is given to illustrate proposed indices and analysis methodology. Simulation and analysis results reveal that proposed transmission indices possess significant advantages, such as normalized finite(ranging from 0 to 1), dimensionally homogeneous,frame-free, intuitive and easy to calculate. Besides, proposed indices well indicate the good transmission region and relativity to the singularity with better resolution than the traditional local conditioning index, and provide a novel tool for kinematic analysis and optimal design of fully parallel manipulators.

Effects of forced cooling on mechanical properties and fracture behavior of heavy section ductile iron

To develop materials suitable for spent-nuclear-fuel containers, the effect of forced cooling on mechanical properties and fracture toughness of heavy section ductile iron was investigated. Two cubic castings with different cooling processes were prepared: casting A was prepared in a totally sand mold, and casting B was prepared in a sand mold with two chilling blocks placed on the left and right sides of the mold. Three positions in each casting with different solidification cooling rates were chosen. In-situ SEM tensile experiment was used to observe the dynamic tensile process. Fracture analysis was conducted to study the influence of vermicular and slightly irregular spheroidal graphite on the fracture behavior of heavy section ductile iron. Results show that the tensile strength, elongation, impact toughness and fracture toughness at different positions of the two castings all decrease with decreasing cooling rate. With the increase of solidification time, the fracture mechanism of conventional casting A changes from ductile fracture to brittle fracture, and that of casting B with forced cooling changes from ductile fracture to a mixture of ductile-brittle fracture.

无功能肾后腹腔镜下个体化手术的临床体会(附84例报告)

目的探讨后腹腔镜下不同解剖层面无功能肾切除的手术方法及临床疗效。方法回顾性分析2010年2月-2016年11月84例良性无功能肾患者临床资料。根据病因、影像及层次特点分别按3个不同解剖层面行后腹腔镜下肾切除,层面为:贴Gerota's筋膜内切除组(A组)、包膜外切除组(B组)、包膜内切除组(C组)。收集3组患者的临床资料及围手术期数据进行统计学分析。结果 C组手术时间及失血量明显大于A、B两组,差异有统计学意义(P<0.05),住院时间、并发症、恢复时间组间差异无统计学意义(P>0.05);结核与非特异性感染病例手术时间与失血量大于其他病例组,差异有统计学意义,余数据差异无统计学意义;84例均在后腹腔镜下获成功,术后1例切口感染,随访6~84个月恢复良好。结论感染性疾病肾周存在的粘连最为严重,包膜内肾切除手术复杂但为严重粘连肾切除的最佳术式,选择正确的相对无血管层面是手术成功的关键。

Basal physiological parameters in domesticated tree shrews(Tupaia belangeri chinensis)

Establishing non-human primate models of human diseases is an efficient way to narrow the large gap between basic studies and translational medicine.Multifold advantages such as simplicity of breeding,low cost of feeding and facility of operating make the tree shrew an ideal non-human primate model proxy.Additional features like vulnerability to stress and spontaneous diabetic characteristics also indicate that the tree shrew could be a potential new animal model of human diseases.However,basal physiological indexes of tree shrew,especially those related to human disease,have not been systematically reported.Accordingly,we established important basal physiological indexes of domesticated tree shrews including several factors:(1)body weight,(2)core body temperature and rhythm,(3)diet metabolism,(4)locomotor rhythm,(5)electroencephalogram,(6)glycometabolism and(7)serum and urinary hormone level and urinary cortisol rhythm.We compared the physiological parameters of domesticated tree shrew with that of rats and macaques.Results showed that(a)the core body temperature of the tree shrew was 39.59±0.05°C,which was higher than that of rats and macaques;(b)Compared with wild tree shrews,with two activity peaks,domesticated tree shrews had only one activity peak from 17:30 to 19:30;(c)Compared with rats,tree shrews had poor carbohydrate metabolism ability;and(d)Urinary cortisol rhythm indicated there were two peaks at 8:00 and 17:00 in domesticated tree shrews,which matched activity peaks in wild tree shrews.These results provided basal physiological indexes for domesticated tree shrews and laid an important foundation for diabetes and stress-related disease models established on tree shrews.

Effect of Cu content on microstructures and mechanical properties of ADI treated by twostep austempering process

The effect of Cu content on the microstructures and mechanical properties (yield strength, ultimate tensile strength, impact energy, fracture toughness) of austempering ductile iron (ADI) treated by two-step austempering process were investigated. High Cu content in nodular cast irons leads to a significant volume fraction of retained austenite in the iron after austempering treatment, but the carbon content of austenite decreases with the increasing of Cu content. Moreover, austenitic stability reaches its maximum when the Cu content is 1.4% and then drops rapidly with further increase of Cu. The ultimate tensile strength and yield strength of the ADI firstly increases and then decreases with increasing the Cu content. The elongation keeps constant at 6.5% as the Cu content increases from 0.2% to 1.4%, and then increases rapidly to 10.0% with further increase Cu content to 2.0%. Impact toughness is enhanced with Cu increasing at first, and reaches a maximum 122.9 J at 1.4% Cu, then decreases with the further increase of Cu. The fracture toughness of ADI shows a constant increase with the increase of Cu content. The influencing mechanism of Cu on austempered ductile iron (ADI) can be classified into two aspects. On the one hand, Cu dissolves into the matrix and functions as solid solution strengthening. On the other hand, Cu reduces solubility of C in austenite and contributes more stable retained austenite.

视网膜静脉阻塞发生发展的眼部生物标记物研究进展

视网膜静脉阻塞(RVO)是仅次于糖尿病视网膜病变(DR)的第二大常见的视网膜血管性疾病。近年研究陆续发现,一些眼部辅助检查得到的指标或征象可预示疾病的发生发展及视力结局,我们称之为眼部生物标记物(biomarker),如视网膜内层结构紊乱(DRIL)、急性黄斑旁中心中层视网膜病变(PAMM)、突出的中界膜征(p-MLM)、视网膜内高反射灶(HRF)、视网膜下液(SRF)、椭圆体带(EZ)、外界膜(ELM)及浅表毛细血管丛(SCP)与深层毛细血管丛(DCP)等。本文就RVO的眼部生物标记物进行综述,希望通过这些指标从多维度观察RVO的发生及发展,对RVO预后判断提供指导,更全面地认识该疾病,并避免严重的视力结局。

Impact of different stereoisomers of inositol on insulin sensitivity of gestational diabetes mellitus patients

BACKGROUND Inositol is a hexa-carbon polyol,a naturally soluble vitamin,often found in various foods.AIM To discuss the impact of different stereoisomers of inositol on insulin sensitivity of gestational diabetes mellitus(GDM)patients.METHODS Eighty GDM pregnant women were divided into four groups according to their treatment received:A group(placebo folic acid 400μg/d),B group[myo-inositol(MI)1500 mg,twice a day],C group[D-chiro-inositol(DCI)250 mg,twice a day],and D group(inositol MI and inositol DCI 1500 mg/250 mg,twice a day).Each patient routinely used dietary guidance adjustments and did some safe and effective aerobic exercise in addition to receiving placebo or inositol from GDM diagnosis to delivery.Triglyceride,total cholesterol,fasting plasma glucose,oral glucose tolerance test postprandial glucose(2 h postprandial blood glucose),fasting insulin,fasting plasma glucose,and glycosylated hemoglobin levels and Homeostasis Model Assessment-insulin resistance(HOMA-IR)and Homeostasis Model Assessment-insulin sensitivity index(HOMA-ISI)scores were determined before treatment and 8 wk after treatment onset.Adverse maternal and infant outcomes,including hypoglycemia,excessive amniotic fluid,premature infants,macrosomia,fetal distress etc.,were also recorded.RESULTS There was no statistical difference in the baseline data of each group.The levels of 2 h blood glucose,glycosylated hemoglobin,fasting insulin,total cholesterol,and triglyceride in the B,C,and D groups were significantly lower than those in the control group(A group)after treatment(P<0.05).Moreover,compared with the B group,the level of the above indexes in the C and D groups decreased more significantly,and the differences were statistically significant(P<0.05).The HOMA-IR of B,C,and D groups decreased significantly,and the HOMA-ISI increased significantly compared with the A group,and the differences were statistically significant(P<0.05),among which the decrease of HOMA-IR and the increase of HOMA-ISI were more significant in the C and D group compared with the B group(P<0.05).The occurrence rate of adverse maternal and infant outcomes in the C and D group was significantly lower than that in the control group(A group),and the differences were statistically significant(P<0.05).CONCLUSION Treatment with different inositol stereoisomers(inositol MI and inositol DCI)can improve insulin sensitivity and reduce insulin resistance in diabetic patients,and inositol DCI has a better curative effect than inositol MI.

One-pot synthesis and optical properties of In- and Sn-doped ZnO nanoparticles

Colloidal indium-doped zinc oxide(IZO) and tin-doped zinc oxide(ZTO) nanoparticles were successfully prepared in organic solution,with metal acetylacetonate as the precursor and oleylamine as the solvent. The crystal and optical properties were characterized by X-ray diffraction,UV?visible spectrophotometry,and fluorescence spectroscopy,respectively; the surface and structure morphologies were observed by scanning electron microscopy and transmission electron microscopy. The XRD patterns of the IZO and ZTO nanoparticles all exhibited similar diffraction peaks consistent with the standard XRD pattern of Zn O,although the diffraction peaks of the IZO and ZTO nanoparticles were slightly shifted with increasing dopant concentration. With increasing dopant concentration,the fluorescent emission peaks of the IZO nanoparticles exhibited an obvious red shift because of the difference in atomic radii of indium and zinc,whereas those of the ZTO nanoparticles exhibited almost no shift because of the similarity in atomic radii of tin and zinc. Furthermore,the sizes of the IZO and ZTO nanoparticles distributed in the ranges 20–40 and 20–25 nm,respectively,which is attributed to the difference in ionic radii of indium and tin.

Preparation and characterization of oil-soluble In_2O_3 nanoparticles and In_2O_3–SnO_2 nanocomposites and their calcined thin films

在油可溶<潜水艇class=“ a-plus-plus ”> 2 O <潜水艇class=“ a-plus-plus ”> 3 nanoparticles 并且在里面<潜水艇class=“ a-plus-plus ”> 2 O <潜水艇class=“ a-plus-plus ”> 3 SnO <潜水艇class=“ a-plus-plus ”> 2 nanocomposites 经由金属 acetylacetonate 先锋的分解在 oleylamine 被准备。薄电影在里面<潜水艇class=“ a-plus-plus ”> 2 O <潜水艇class=“ a-plus-plus ”> 3 并且在里面<潜水艇class=“ a-plus-plus ”> 2 O <潜水艇class=“ a-plus-plus ”> 3 SnO <潜水艇class=“ a-plus-plus ”> 2 被纺纱涂层答案获得在油可溶<潜水艇class=“ a-plus-plus ”> 2 O <潜水艇class=“ a-plus-plus ”> 3 nanoparticles 并且在里面<潜水艇class=“ a-plus-plus > 2 O <潜水艇class= a-plus-plus > 3 SnO <潜水艇class= a-plus-plus > 2 nanocomposites 到底层上然后锻烧他们。传播电子 microspectroscopy，扫描电子 microspectroscopy，原子力量 microspectroscopy， X 光检查衍射， ultravioletvisible 吸收，和光致发光光谱学被用来调查 nanoparticles 和薄电影的性质。在里面 < 潜水艇 class= “ a-plus-plus ” > 2 O < 潜水艇 class= “ a-plus-plus ” > 3 nanoparticles 是有 ~ 的一条直径的立方阶段的范围 8 nm；他们的系列展出了在 348 nm 集中的一座宽广排放山峰。在里面<潜水艇class=“ a-plus-plus ”> 2 O <潜水艇class=“ a-plus-plus ”> 3 SnO <潜水艇class=“ a-plus-plus ”> 2 nanocomposites 是创作的合作粒子在更小<潜水艇class=“ a-plus-plus ”> 2 O <潜水艇class=“ a-plus-plus “> 3 个粒子和更大的 SnO <潜水艇class=” a-plus-plus “> 2 个粒子；他们的系列在 355 nm 展出了一座宽广排放山峰。在以后在里面 < 潜水艇 class= “ a-plus-plus ” > 2 O < 潜水艇 class= “ a-plus-plus ” > 3 SnO < 潜水艇 class= “ a-plus-plus ” > 2 nanocomposites 在 400

Microstructure and mechanical properties of twostep Cu-alloyed ADI treated by different second step austempering temperatures and times

Austempering ductile iron (ADI) is an attractive material due to its excellent comprehensive mechanical properties. However, the deficit in elongation and toughness always threatens its security application. Two-step austempering process is an effective way to improve elongation and toughness simultaneously. In the present work, the influence of the amount, morphology and distribution of ferrite and austenite on mechanical properties of ADI under different second-step austempering parameters has been analyzed. Results show that the amount of austenite and its carbon content decrease with increasing of second-step temperature. Carbide begins to precipitate as second-step austempering temperature reaches 380 °C. These factors together influence the mechanical properties of two-step Cu-alloyed ADI. Impact energy and fracture toughness are strongly affected by second-step austempering temperature, and are dramatically decreased with increase of second-step austempering temperature. Elongation remains constant when the second-step temperature is below 360 °C, and then it is rapidly decreased with further increase of second-step temperature. Strength is slightly influenced by second-step temperature. Ferrite morphology is not influenced by second-step austempering duration, while blocky retained austenite size is slightly decreased with the increasing of second-step austempering time. The amount of retained austenite is decreased while the carbon content of retained austenite is increased with the extending of second-step austempering time. The substructure of austenite is transformed from dislocation to twin when second-step austempering time exceeds 60 min. Strength and elongation are improved slightly with extending of second-step time. Impact energy and fracture toughness initially decrease with the extending of second-step time, and then remain constant when the time is longer than 60 min. This is a result of austenite content decreasing and carbon content of austenite increasing. The second-step austempering time mainly influences austenite content and its carbon content, which is a result of carbon diffusion behavior variation.