Si_3N_4 nano-microsphere synthesized by cathode arc plasma and heat treatment

The Si3N4 microcrystals with a hollow sphere structure were prepared by using the simple heat treatment of the Si3N4 flakes, which were prepared by using the cathode arc plasma. The products were characterized by XRD, SEM and TEM. The photoluminescence (PL) spectrum of the Si3N4 nano-microsphere was studied. The obtained Si3N4 microcrystals, which show a hollow sphere structure, are up to several nanometers in diameter. During the process, the heat treatment and Ni catalyst play a key role in the forming structure and morphology. This result provides a possibility for mass producing Si3N4 microcrystals.

Quick Surface Treatment of AZ31B by AC Micro-arc Oxidation

In order to explore an effective way to shorten treatment time and enhance the quality of treatment coating, AC micro-arc oxidation was conducted to treat the surface of AZ31 B deformation magnesium alloy in KF＋KOH treatment solution. The infl uences of micro-arc oxidation parameters such as concentration of KF, concentration of KOH, output voltage of booster, temperature of treatment solution, and treatment time on treatment coating thickness were raveled out under different conditions. The structure and composition of treatment coating were determined, the growth mechanism of treatment coating was discussed, and the quick surface treatment technology for compact treatment coating with maximum thickness was developed. The experimental results show that： A maximum 33 μm-thick compact treatment coating, consisting of MgF2 and MgO mainly, can be formed on AZ31 B in 112 s under the conditions of 1 132 g/L KF, 382 g/L KOH, 66 V for output voltage of booster and 34 ℃ of treatment solution which were optimized by a genetic algorithm from the model established by artifi cial neural networks. There are no ＂crater-shaped＂ pores in this treatment coating as the heat shock resulting from the smooth variation of AC sinusoidal voltage is far smaller than that of the rigidly varied DC or pulse current. The treatment time is only one sixth of that adopted in the other surface treatment technology at best, principally for the reason that the coating can always grow irrespective of the electric potential of AZ31 B. This investigation lays a fi rm foundation for the extensive application of magnesium alloy.

直肠癌和宫颈癌容积调强计划的ArcCheck三维剂量验证应用分析

目的探究ArcCheck-3DVH在直肠癌与宫颈癌调强放疗计划上的三维剂量验证效果,并探讨该设备在2组计划剂量验证结果上的差异。方法选取基于Monaco 6.1计划系统的19例直肠癌与21例宫颈癌计划为研究对象。采用SNC Patient计算并比较diff/Dist=3 mm/3%、阈值TH=10条件下放疗计划系统(Treatment Planning System,TPS)与ArcCheck模体测得的γ通过率。再采用3DVH系统重建靶区与危及器官的三维剂量分布,比较其与TPS在D98%(98%的靶区体积接受的最小剂量)、D_(2%)(2%的靶区体积接受的最小剂量)和D_(mean)(平均剂量)等参数条件下的剂量差异。结果19例直肠癌计划在SNC Patient上计算得到的平均γ通过率为99.46%±0.70%,大于3DVH的98.88%±0.46%,且剂量差异具有统计学意义(P<0.05)。临床靶区的γ通过率均大于94%且在D_(2%)下剂量差异存在统计学意义(P<0.05)。危及器官的γ通过率均大于95%且除小肠V40(器官接受至少40 Gy剂量的体积百分比)、脊髓D_(mean)外,其余危及器官在各参数下差异均无统计学意义(P>0.05)。21例宫颈癌计划在SNC Patient上计算得到的γ通过率为99.67%[99.35%,99.95%],大于3DVH的98.49%[98.05%,98.95%],且两者之间的差异具有统计学意义(P<0.05)。临床靶区的γ通过率均大于93.70%并在D_(mean)和D_(2%)下的剂量差异具有统计学意义(P<0.05)。危及器官的γ通过率均大于91%,且除直肠V30(器官接受至少30 Gy剂量的体积百分比)、脊髓D_(mean)外,其余器官在各参数下的剂量差异均具有统计学意义(P<0.05)。结论ArcCheck-3DVH系统不仅能整体评估直肠癌和宫颈癌容积旋转调强放疗计划的剂量验证结果,还能进一步提供靶区与危及器官的测量重建剂量和与TPS计算剂量之间的差异。

MONACO放疗计划系统VMAT计划照射野Arc数目对治疗计划影响的比较分析

目的评价MONACO治疗计划系统中VMAT计划照射野不同Arc数目对剂量分布、计划执行以及剂量验证通过率的影响。方法对接受治疗32例宫颈癌患者进行了回顾性分析,原执行治疗的计划为设置两个射野,每个射野1个Arc(1 Arc Per Beam,1APB),在原治疗计划轮廓勾画和参数约束相同的情况下,将照射野参数改为一个射野,每个射野2个Arc(2 Arc Per Beam,2APB)。计划在保证靶区100%体积接受95%处方剂量的标准下,对靶区的适形指数、均匀指数,危及器官的受照剂量,治疗计划的机器跳数和控制点数以及治疗计划的执行时间和剂量验证通过率进行评估。结果两种计划靶区的适形指数和均匀指数均值相近,危及器官受照剂量均值相近,差异无统计学意义(P>0.05)。与1APB计划相比,2APB计划的机器跳数和控制点数明显减少(P<0.05);在计划执行方面,2APB计划比1APB计划的实施时间明显缩短(P<0.05);而在两种计划的剂量输出验证方面,剂量通过率相近,差异无统计学意义(P>0.05)。结论两种治疗计划的剂量学差异相近,均能满足临床要求,但是2APB计划比1APB计划的执行效率有大幅提升,可在减少治疗机损耗的基础上提升了整体工作效率。

多学科诊疗联合ARCS动机模式教学在肿瘤内科住院医师规范化培训中的应用

目的探讨多学科诊疗(multi-disciplinary treatment,MDT)联合ARCS动机模式教学方法在临床肿瘤内科住院医师规范化培训中的应用效果。方法选取2020年1月1日至2021年12月31日在空军军医大学第一附属医院肿瘤科接受住院医师规范化培训的30名学员进行肿瘤内科临床教学,按随机数字表法分为观察组和对照组,每组15例;对照组采用带教老师指导下参与MDT的教学方法,观察组采用MDT联合ARCS动机模式的教学方法。教学前使用调查问卷对两组学员的临床肿瘤学相关理论知识初始掌握程度及学习意愿进行调查分析。教学结束后,对两组学员进行临床肿瘤学理论知识和临床技能考核,使用调查问卷的形式调查两组学员对教学的满意程度、自信心、角色意识及对肿瘤专业的学习兴趣。结果教学前,观察组与对照组对临床肿瘤学相关理论知识的初始掌握程度差异无显著性(t=0.650,P=0.521)。观察组和对照组学员认为肿瘤专业知识对个人临床工作具有帮助的比例分别为100%(15/15)、86.6%(13/15),差异无显著性(χ^(2)=3.686,P=0.298)。教学后,两组学员理论知识得分差异无显著性,观察组文献阅读、临床技能以及考核总分均高于对照组,差异有显著性(P<0.05)。观察组记忆性知识点正确率与对照组比较差异无显著性(t=1.120,P=0.335),应用性知识点正确率高于对照组,差异有显著性(t=2.378,P=0.025)。两组学员对肿瘤内科住培的满意程度评分均较高,在临床能力自我认知的三个问题中,观察组评分均高于对照组,差异有显著性(P<0.05)。教学后,观察组对肿瘤专业的学习兴趣评分明显高于教学前及对照组,差异有显著性(P<0.05)。结论多学科诊疗联合ARCS动机模式教学可有效增强学员对肿瘤学临床教学要点尤其是实践能力的掌握,同时提高了学习主动性和教学满意度,增强了职业信心。

Microstructure and Mechanical Properties of Wire + Arc Additively Manufactured 2050 Al–Li Alloy Wall Deposits

Aluminum–Lithium(Al–Li) alloy is a topic of great interest owing to its high strength and light weight, but there are only a few applications of Al–Li alloy in wire ss, a special AA2050 Al–Li alloy + arc additive manufacturing(WAAM) process. To identify its feasibility in WAAM procewire was produced and employed in the production of straight-walled components, using a WAAM system based on variable polarity gas tungsten arc welding(VP-GTAW) process. The influence of post-deposited heat treatment on the microstructure and property of the deposit was investigated using optical micrographs(OM), scanning electron microscopy(SEM), X-ray diffraction(XRD), hardness and tensile properties tests. Results revealed that the microstructures of AA2050 aluminum deposits varied with their location layers. The upper layers consisted of fine equiaxed grains, while the bottom layer exhibited a coarse columnar structure. Mechanical properties witnessed a significant improvement after post-deposited heat treatment, with the average micro-hardness reaching 141 HV and the ultimate tensile strength exceeding 400 MPa. Fracture morphology exhibited a typical ductile fracture.

Effect of scanning speed during PTA remelting treatment on the microstructure and wear resistance of nodular cast iron

The surface of nodular cast iron （NCI） with a ferrite substrate was rapidly remelted and solidified by plasma transferred arc （PTA） to induce a chilled structure with high hardness and favorable wear resistance. The effect of scanning speed on the microstructure, micro-hardness distribution, and wear properties of PTA-remelted specimens was systematically investigated. Microstructural characterization in-dicated that the PTA remelting treatment could dissolve most graphite nodules and that the crystallized primary austenite dendrites were transformed into cementite, martensite, an interdendritic network of ledeburite eutectic, and certain residual austenite during rapid solidifica-tion. The dimensions of the remelted zone and its dendrites increase with decreased scanning speed. The microhardness of the remelted zone varied in the range of 650 HV0.2 to 820 HV0.2, which is approximately 2.3-3.1 times higher than the hardness of the substrate. The wear re-sistance of NCI was also significantly improved after the PTA remelting treatment.

瓦里安Eclipse计划系统中基于云计算的ARC技术的剂量计算时间的探讨

目的探讨如何缩短基于云计算的ARC技术的剂量计算时间。方法随机选择15例鼻咽癌患者,计划方式选择ARC技术,射野选择四个弧度,计算网格大小选择2.5 mm。对于每一例患者剂量计算时,先选择调用带有Eclipse的2台工作站,记录剂量计算时间,再分别选择调用4,5,6,7,8台工作站,并记录剂量计算时间。结果剂量计算选择调用6台工作站时计算时间最短,选择7台工作站和8台工作站计算时间不但没有缩短,反而略有增加。选择调用6台工作站比2台工作站计算时间平均缩短约19′06″。采用Mann-Whitney U检验,6台工作站与2,4,5,7,8台工作站相比较,Z=-4.667,-2.634,-1.348,-0.415,-1.390,P=0.000,0.008,0.178,0.678,0.165。结论调用6台工作站时所用的计算时间短于2台和4台,具有统计学差异;调用6台工作站时所用的计算时间短于5、7和8台,但不具有统计学差异。局域网中增加一定数量用于计算调用的工作站,能够一定程度的缩短剂量计算的时间,提高肿瘤放疗计划设计的效率。

Effect of solution treatment on microstructure of Inconel 601 nickel-based superalloy weld seam

The microstructure of lneonel 601 nickel-based superalloy after gas tungsten arc welding and its transformation at different solution temperatures are studied. The results show that the original microstructure of weld seam is characterized coarsened austenitic granular crystal, there are a large amount of dispersed carbide and γ＇ phase with carbide as the core in the boundary of grains. Grain of heat-affected zone grows up severely with very little precipitated carbide. The carbide and γ＇ phase are gradually solved into the austenite matrix with the increase of solution treatment temperature. Especicdly solution treated at 1 150 ℃, the carbide and γ＇ phase are completely solved into the austenite matrix, the coarsened equiaxed anstenite grain sizes are refined.

DICOM-RT Plan Complexity Verification for Volumetric Modulated Arc Therapy

The purpose of this study was to investigate the relationship between plan parameters verified with DICOM-RT and dosimetric results for volumetric modulated arc therapy (VMAT). We investigated three treatment locations: prostate cancer (ten cases), maxillary sinus cancer (four cases), and malignant pleura mesothelioma (four cases) with treatment plans generated by a MonacoTM treatment planning system (TPS), and delivered with an Elekta SynergyTM linear accelerator. We calculated plan parameters, including gantry and multileaf collimator (MLC) positions, Monitor Units (MU), and millimeters of MLC motion per degree of gantry rotation (mm/degree), and performed quality assurance (QA) with a DICOM-RT plan verification system. We measured the VMAT dose with a two-dimensional diode array detector. The average gamma passing rate with percent dose acceptance criteria and distance to agreement criteria of 2 mm and 2% (2 mm/2%) were 97.4%, 97.8% and 92.0% for prostate cancer, maxillary sinus cancer, and malignant pleural mesothelioma, respectively. The mean 95th percentile value for DICOM-calculated mm/degree was 4.0, 5.2, and 11.1 for prostate cancer, maxillary sinus cancer, and malignant pleural mesothelioma, respectively. The gamma passing rate showed a correlation with calculated mm/degree, with a coefficient of determination (R2) of 0.60. Higher calculated mm/degree values led to increased dosimetric errors. We conclude that dose distribution calculated by a TPS is more reliable at smaller mm/degree.

ARC／INFO系统在林业图形处理上的应用

本文应用ＡＲＣ／ＩＮＦＯ系统对林业图形的处理进行了分析研究，探讨了林业图形制作自动化及图形信息分析、管理系统化的有效途径。

Microstructure and corrosion behaviour of gas tungsten arc welds of maraging steel

Superior properties of maraging steels make them suitable for the fabrication of components used for military applications like missile covering, rocket motor casing and ship hulls. Welding is the main process for fabrication of these components, while the maraging steels can be fusion welded using gas tungsten arc welding(GTAW) process. All these fabricated components require longer storage life and a major problem in welds is susceptible to stress corrosion cracking(SCC). The present study is aimed at studying the SCC behaviour of MDN 250(18% Ni) steel and its welds with respect to microstructural changes. In the present study, 5.2 mm thick sheets made of MDN 250 steel in the solution annealed condition was welded using GTAW process. Post-weld heat treatments of direct ageing(480 C for 3 h), solutionizing(815 C for 1 h) followed by ageing and homogenizing(1150 C for 1 h) followed by ageing were carried out. A mixture of martensite and austenite was observed in the microstructure of the fusion zone of solutionized and direct aged welds and only martensite in as-welded condition. Homogenization and ageing treatment have eliminated reverted austenite and elemental segregation. Homogenized welds also exhibited a marginal improvement in the corrosion resistance compared to those in the as-welded, solutionized and aged condition. Constant load SCC test data clearly revealed that the failure time of homogenized weld is much longer compared to other post weld treatments, and the homogenization treatment is recommended to improve the SCC life of GTA welds of MDN 250 Maraging steel.

Complex Target Volume Delineation and Treatment Planning in Radiotherapy for Malignant Pleural Mesothelioma (MPM)

Introduction: Radiotherapy alone or combined with surgery and/or chemotherapy is being investigated in the treatment of malignant pleural mesothelioma (MPM). This study aimed to simulate a Volumetric Modulated Arc Therapy (VMAT) treatment of a patient with MPM. Materials and Methods: CT images from a patient with intact lungs were imported via DICOM into the Pinnacle3 treatment planning (TP) system (TPS) and used as a model for MPM to delineate organs at risk (OAR) and both clinical and planning target volumes (CTV and PTV) with a margin of 5 mm. Elekta Synergy with 6 MV photons and 80 leafs MLCi2 was employed. VMAT plans were generated using two coplanar arcs with gantry rotation angles of 178° - 182°, the collimator angles of each arc were set to 90°, Octavius® 4D 729 was employed for quality assurance while the calculated and measured doses were compared using VeriSoft. Results: A TP was achieved. The Gamma volume analysis with criteria of 3 mm distance to agreement and 3% dose difference yielded the gamma passing rate = 99.9%. The reference isodose was 42.75 Gy with the coverage constraints for the PTV D95 and V95 = 95.0% of 45 Gy. The remaining dosimetric parameters met the recommendations from the clinically acceptable guidelines for the radiotherapy of MPM. Conclusion: Using well-defined TV and VMAT, a consistent TP compared to similar ones from publications was achieved. We obtained a high agreement between the 3D dose reconstructed and the dose calculated.

等离子电弧双丝增材制造Ti-48Al合金组织特征

采用等离子电弧双丝增材制造技术成功制备了Ti-48Al合金(at.%),并对其沉积态和热处理后的组织特征进行了系统地研究.结果表明,沉积态Ti-48Al合金主要由α2相和γ相组成,沿着沉积方向,沉积态组织呈现由树枝晶区和片层晶团区交替分布的不均匀性特征,并且在树枝晶区存在严重的枝晶间Al元素偏析现象.在1 340℃/10 h/炉冷热处理后,不均匀的沉积态组织转变为晶粒尺寸细小的双态组织,Ti-48Al合金的微观组织的不均匀性获得明显改善,并且α2相含量显著增加,组织的择优取向减弱.

退火处理对电弧增材AZ31镁合金阻尼及力学性能的影响

为了探索热处理优化电弧增材镁合金阻尼性能的方案,对TIG电弧增材AZ31镁合金进行了去应力退火和完全退火4、5 h处理,并对原始试样和退火后的试样微观组织、阻尼性能和力学性能进行了对比分析。研究表明:与原始增材试样相比,所有退火后的试样在低振幅下的阻尼性能均有所下降,当振幅超过20μm后阻尼性能有所提升;但去应力退火试样在超过20μm后的阻尼性能提升较小,完全退火4、5 h试样的阻尼性能相近,均比原始增材试样有所提升,表明退火时长对阻尼性能影响不大。在力学性能方面,去应力退火和完全退火4 h的试样的抗拉强度与原始试样相差不大,完全退火5 h的试样略有下降,去应力退火试样的伸长率与原始试样的伸长率相差不大,但是完全退火试样的伸长率均得到了提升。

镁合金微弧氧化膜致密化技术研究进展

镁合金作为轻质结构材料,在装备轻量化领域展示了巨大的应用潜力。由于镁合金的化学活性较高,表面生成的氧化膜疏松多孔,严苛的服役环境对其长效稳定性构成严重威胁。采用表面防护技术有效提升镁合金的耐蚀性,延长其使用寿命。在镁合金表面改性防护技术中,微弧氧化技术具有显著的技术特征,被认为是最有前景的镁合金表面防护技术之一。然而镁合金微弧氧化膜存在本质的多孔结构特征,影响膜的防护效果。为扩大镁合金的应用领域,需要对微弧氧化膜进行致密化处理。本文综述了镁合金微弧氧化膜致密化技术的发展概况,总结了微弧氧化膜致密化技术的主要策略,以期为高致密镁合金微弧氧化膜的设计提供理论指导。最后,对镁合金微弧氧化膜致密化技术的未来发展趋势进行了展望。

热处理对电弧增材制造TC4钛合金组织和性能影响的研究进展

电弧增材制造(WAAM)TC4钛合金相比传统制造工艺具有成本低,沉积速率高等优势,应用前景广阔。然而电弧沉积过程会使材料微观组织结构不均匀、产生残余应力,造成其力学性能的各向异性,故需采用合适的热处理工艺以消除不利影响、进一步满足使用性能要求。本文综述了近年来国内外关于热处理调控电弧增材制造TC4合金组织性能方面的相关文献,全面分析了热处理对TC4合金等轴晶形成及细化的影响机制,讨论了热处理工艺对TC4合金强度、塑性、硬度、疲劳、抗蠕变等力学性能的影响因素与作用机理,最后对WAAM热处理工艺对调控TC4合金组织和性能的研究进行了展望。

热处理对电弧增材制造马氏体沉淀硬化不锈钢组织性能的影响

马氏体沉淀硬化不锈钢在增材制造过程中,由于反复的热循环和热积累,材料的组织和性能可能会出现不均匀或缺陷。以自研药芯焊丝为原材料,采用电弧增材制造技术制造马氏体沉淀硬化不锈钢结构件,由于电弧增材过程中受到复杂的热循环,因此增材件组织不均匀,导致机械性能下降。采用固溶、时效以及固溶+时效三种热处理工艺对结构件进行处理,并利用金相显微镜、扫描电子显微镜、维氏硬度计和拉伸试验机等设备对试样的显微组织、成分、硬度和拉伸性能进行分析。结果表明,热处理态试样组织转变为马氏体且伴有强化相析出,其中固溶+时效处理效果最佳,极限抗拉强度与硬度分别达到1 048.53 MPa与423.5 HV,相比于沉积态分别提升了211.53 MPa与106.8 HV。但热处理态试样的断后伸长率相比于沉积态试样的有所降低。

电弧增材制造GH4169合金均匀化热处理组织特征、力学性能和蠕变性能研究

为深入探究电弧增材制造GH4169合金热处理组织特征,针对不同热处理工艺对GH4169合金组织及相的影响开展研究,以确定最佳的均匀化热处理工艺。采用电弧熔丝增材制造技术成形GH4169合金试块,研究不同均匀化热处理温度下试样微观组织和力学性能的变化。结果显示,随着均匀化温度的提升,Laves相逐渐溶解至完全溶解,试样组织逐渐变得均匀。当均匀化温度升至1 100℃时,Laves相完全溶解,试样水平方向和垂直方向均为等轴晶,组织各向异性消除。经过1 100℃均匀化处理再进行固溶+双时效处理,材料强度明显提升,相比沉积态增加50%,且材料的蠕变性能远高于锻件标准。研究表明,通过控制均匀化热处理温度和后续的热处理工艺,能有效提升电弧增材制造GH4169合金的力学性能和蠕变性能。对于优化电弧增材制造GH4169合金的工艺参数,提高其综合性能具有重要意义。

热处理对超低碳CrMnN奥氏体不锈钢焊接接头性能的影响

采用等离子弧焊接对QN1804L(下称18Cr)超低碳CrMnN奥氏体不锈钢进行焊接,并对焊接接头分别进行形变热处理和固溶处理。结果表明:焊态下接头组织由奥氏体和铁素体组成,铁素体呈骨架和板条状分布在奥氏体组织中间,焊缝硬度略高于母材的;形变热处理后焊缝组织发生扭曲,晶粒被拉长,焊缝硬度远高于母材的;同时由于形变强化,焊缝强度也明显提高。固溶处理后焊缝中的铁素体在高温转变为奥氏体,未及时转变的呈点状分布,焊缝硬度与母材的基本保持一致;不同热处理后的焊缝均具有较好的耐腐蚀性能。