电子束钎焊接头组织分析

采用自主开发的电子束钎焊系统,对不锈钢毛细管板结构进行钎焊,通过电子探针显微分析仪研究了不同电子束钎焊规范下BNi-2钎料与管壁基体界面合金元素的分布,分析了钎料和界面区各相的化学组成.研究表明:在加速电压60kV,束流6.5 mA,加热时间37 s,扫描幅值O.5的电子束钎焊规范下,管板接头质量满足技术规范要求;随着电子束输入功率或功率密度增大,钎料和管壁的相互扩散作用增强,导致过渡层厚度增加,毛细管壁显著减薄;母材和钎料中合金元素的相互扩散导致过渡层的形成,过渡层主要由硼化铬、硼化镍和镍的固溶体组成.     

镍、铁基喷焊层组织与性能研究

为寻找具有耐盐酸腐蚀能力的喷焊用合金粉末,自行设计了3种喷焊粉末,并对比研究了自制粉末与商业Ni60粉氧乙炔喷焊层的显微硬度、显微组织形貌和耐盐酸腐蚀性能.结果表明,自制1号粉喷焊层的显微硬度值明显高于商业Ni60喷焊层,自制2号粉喷焊层的显微硬度和耐蚀性均优于商业Ni60喷焊层.分析认为,钼的加入可改善合金粉末的喷焊工艺性,提高喷焊层的耐盐酸腐蚀性能;铬含量的增加显著提高了喷焊层的显微硬度;喷焊层中铁含量的增加对耐盐酸腐蚀性能有不利影响.     

铝锌硅镀层的冲压性能

铝锌硅镀层(Galvalume)作为钢铁基体的热浸镀材料,具有良好的耐腐蚀能力,但是Galvalume镀层在受力变形时容易出现裂纹。针对热浸镀Galvalume镀层成形开裂问题,通过对不同镀层厚度(重量)镀铝锌板进行冲压试验和180°弯曲试验,观察裂纹源的产生。采用扫描电镜(SEM)和能谱(EDS)对镀层及中间过渡层进行研究,分析影响镀层冲压开裂的原因。结果显示:镀层的重量(厚度)是影响其冲压开裂的主要原因,随着镀层厚度的下降,镀层外侧受拉应力作用开裂趋势变小;开裂位置显示主要元素为Fe、Al、Si元素,变形过程中Galvalume合金过渡层相对于镀层更容易开裂;Galvalume合金过渡层的厚度是影响Galvalume冲压开裂的主要原因,随着合金过渡层厚度的降低,过渡层开裂趋势变小。     

混凝土桥梁金属配件粉末渗锌防腐蚀层研究

实验室小型共渗炉内制备的试样与工业化渗层试样在结构和性能方面不同。为更合理地评价工业化渗层质量,通过工业随炉共渗制备渗锌小尺寸试样,分析了渗锌防腐蚀层的厚度、微观结构、元素分布、硬度,并测试其耐盐雾性能。结果表明:渗锌后工件表面结构可分为Zn-Fe合金层和含Zn过渡层,Zn-Fe合金层在表层,Zn含量较高,是防腐蚀防锈的主要结构层; Zn-Fe合金层与铁基体的界面过渡层厚度约20μm,Zn-Fe合金层与基体结合紧密;渗锌温度高、保温时间长有助于提高工件表面渗层厚度,随炉渗锌小尺寸试样增重法测得的渗层厚度最小,较适用于监控每炉工件共渗质量;合金层硬度高于基体,硬度向基体方向逐步降低,合金层和离界面60μm处的硬度均高于基体30 HV以上,可提高工件表面的耐磕碰性能;常用渗锌温度(420℃)热处理对工件表面硬度无影响,渗锌工件表面硬度增加主要在于表面形成了合金层;随着渗锌层厚度增加,渗层样品耐盐雾性能逐渐提高,渗层厚度宜≥60μm。     

磁控溅射电流对刀具表面Al/Cr-DLC膜组织和力学性能的影响

为获得膜基结合力更高的刀具,选择Al/Cr金属作为过渡层,分析了不同溅射电流下Al/Cr-DLC膜的组织和力学性能,膜厚都在1.50～ 1.70 μm左右.结果 显示:随着溅射电流增加,过渡层厚度变化不明显;增大溅射电流后,膜层中的Cr、Al比例也随之增加,过渡层可以促进元素更快扩散;各膜层拉曼光谱都在1000～2000 cm-1区间形成了非晶碳的非对称峰.随着溅射电流的增大,Cr、Al元素在膜中的含量也明显提高.增大溅射电流后,膜层中形成了更高比例的Al和Cr,而ID/Ic的比值先增大再减小,最大比值出现于3.0 A电流下.逐渐增大溅射电流的过程中,残余应力先减小再升高,最低残余应力出现于溅射电流为3.0 A下.当膜层中存在过渡层时,内应力发生了显著降低.当溅射电流由1.0A升高至3.0 A时,膜层的硬度和弹性模量都出现了降低.     

15-5PH不锈钢表面多弧离子镀高结合性能TiN膜层研究

多弧离子镀方法在15-5PH不锈钢材料表面制备结合力、硬度和致密性高的TiN涂层,提高材料表面硬度和抗高温氧化性能。分析结果显示过渡层成分、预热温度、工作气压及负偏压等主要参数对膜层性能影响明显。得到Ti为过渡层时,预热250℃,气压3.0Pa,600V偏压镀膜工艺参数最佳,制备的膜基结合力高于60N,表面硬度>1200HV0.05,膜层表面大液滴密度尺寸最低。膜层表面显微硬度、膜层沉积速率和膜基结合力随工作气压升高不同程度地先升高后降低。     

缝纫机针杆表面沉积含过渡层DLC薄膜及性能的研究

本文以C2H2为碳源,Ar气为辅助气体,采用新型离子束源和磁控溅射源的混合技术在缝纫机针杆上成功制备了具有不同过渡层的类金刚石薄膜,并表征了薄膜的表面形貌,测量了其硬度、结合力、摩擦系数,划痕法的结果表明,增加过渡层后薄膜的结合状况得到明显改善.DLC膜的硬度也得到了提高,摩擦磨损实验结果可以看出样品的摩擦系数均在0.1以下,可以极大地改善不锈钢针杆的摩擦性能.     

射频磁控溅射法沉积SiC-Al薄膜的摩擦特性

利用射频法非平衡磁控溅射设备在钛合金板上沉积了非晶态SiC-Al薄膜。为了降低薄膜的摩擦系数,在薄膜中添加Al原子,同时Al也被选择为中间过渡材料来提高界面结合强度和防止界面氧化。研究结果表明:薄膜摩擦系数随着Al原子含量的增加而先减后增,并在Al含量为0.97%时达到最小值。SiC-Al薄膜对SiC和Al2O3陶瓷材料的摩擦系数比对不锈钢材料的摩擦系数低,但它与SUJ2轴承钢之间的摩擦系数最低,在0.04~0.07之间。当把Al作为中间过渡材料时,SiC-Al薄膜的破坏寿命达到了20000循环以上,明显改善了薄膜的界面结合强度;当Al中间过渡层的厚度超过0.2μm以上时,薄膜破坏表现为磨损而不发生剥离现象。另外,薄膜的耐磨强度随着Al含量的增加有所增强。     

Cu-Be/Cu-Zn层状金属基复合材料的冷轧变形行为及界面过渡层演变

高铍含量的铍铜(Cu-Be)合金时效后抗拉强度可达1400 MPa以上,伸长率却不到5％,呈现显著的强度-塑性倒置关系,严重影响了合金服役的安全可靠性.高强Cu-Be合金塑性变形时产生的局部应变集中现象是导致其低塑性的根本原因,将层状非均质构型设计的思想运用于Cu-Be合金,构建Cu-Be/Cu-Zn层状金属基复合材料,可以有效减少该现象的产生,有望获得高强塑性的层状金属基复合材料.运用塑性变形法制备层状金属基复合材料简单易行,受到广泛关注.前人对层状金属基复合材料轧制变形规律的研究主要集中在复合材料金属组元方面,对界面过渡层变形规律研究较少.本工作利用真空热压复合及后续冷轧变形的方式制备了Cu-Be/Cu-Zn层状金属基复合材料,利用光学显微镜(OM)、场发射扫描电镜(FE-SEM)结合能谱仪(EDS)、显微维氏硬度计对Cu-Be/Cu-Zn层状金属基复合材料冷轧变形行为及界面过渡层的演变进行了研究.研究结果表明,Cu-Be/Cu-Zn层状金属基复合材料冷轧前金属层间界面基本呈平直状,界面结合良好且无裂纹、孔洞等缺陷.当冷轧压下率不超过50％时,Cu-Be/Cu-Zn层状金属基复合材料发生不均匀的宏观变形,Cu-Zn层在板材厚度方向的变形量明显大于Cu-Be层和界面过渡层,当冷轧压下率为35％时,界面过渡层的厚度仅减小8.3％,不均匀的塑性变形导致Cu-Be/Cu-Zn界面由平直状态变为波浪状态;当冷轧压下率超过65％时,层状金属基复合材料内部发生均匀、协调的变形,各层厚度基本按照总冷轧压下率变化.不同冷轧压下率下,显微硬度最高的均为过渡层,其次是Cu-Be层,而Cu-Zn层的显微硬度最低.这是因为在层状金属基复合材料冷轧变形过程中,界面过渡层主要起到协调变形的作用,处于显著剪切应力状态,会产生额外的背应力强化.本工作探讨了界面过渡层在Cu-Be/Cu-Zn层状金属基复合材料冷轧过程中的宏观变形以及强化机理,有助于进一步阐明层状金属基复合材料塑性加工变形规律并合理制定其塑性加工工艺.     

过渡合金层对激光多层堆焊组织性能影响

采用45钢作为基体材料,在不预热情况下通过增加过渡合金粉堆焊层,再选用专用焊丝进行堆焊试验。由于过渡合金粉中的Ni、Cr提高的奥氏体的稳定性,产生FeNi缓解了高硬度焊丝中碳化物内产生的残余应力,多次堆焊加热使其热应力在该区域得到缓解,减少了裂纹倾向,同时焊丝中的C、V等形成碳化物,因此提高了堆焊层的硬度。     

Effect of rhenium addition on fracture toughness of tungsten at elevated temperatures

Fracture toughness tests of tungsten and tungsten-rhenium alloy specimens were carried out at elevated temperatures. Temperature dependence of fracture toughness and effect of rhenium content on fracture toughness were investigated. Although fracture toughnesses of three kinds of specimens with rhenium contents of 0, 5 and 10 wt% were almost identical at room temperature, fracture toughness at elevated temperatures increased with increasing rhenium content. The brittle-ductile transition, similar to steels, and subsequent transition of the fracture mode from ductile dimple to intergranular were observed for all three kinds of specimens. With increasing rhenium content, the transition temperatures increased. A significant grain growth was found, not for tungsten-rhenium alloy specimens, but for a tungsten specimen without rhenium in a temperature range higher than the recrystallizing temperature, which resulted in transition of the fracture mode from dimple to intergranular.     

Modeling ductile to brittle transition temperature of functionally graded steels by fuzzy logic

In this article, a model based on fuzzy logic (FL) for predicting ductile to brittle transition temperature of functionally graded steels in both crack divider and crack arrester configurations has been presented. Functionally graded steels containing graded ferritic and austenitic regions together with bainite and martensite intermediate layers were produced by electroslag remelting. For purpose of building the model, training and testing using experimental results from 140 specimens produced from two basic composites were conducted. The used data as inputs in FL models are arranged in a format of six input parameters that cover the FGS type, the crack tip configuration, the thickness of graded ferritic region, the thickness of graded austenitic region, the distance of the notch from bainite or martensite intermediate layer, and temperature. According to these input parameters, in the FL, the ductile to brittle transition temperature of each FGS specimen was predicted. It has been found that FL model will be valid within the ranges of variables. The training and testing results in the FL model have shown a strong potential for predicting the ductile to brittle transition temperature of each FGS specimen.     

电弧熔覆韧-硬复合层工艺及性能研究

目的 为增强Q960E钢表面的使用性能、减少裂纹的产生,设计并制备了一种韧-硬复合梯度过渡熔覆层。方法 通过实验比对,选出了适合的过渡层与高硬层熔覆材料。首先选择XY-26F-104合金粉末作为熔覆材料,用TIG焊将材料熔覆在基板上作为过渡层,其次采用CO2气体保护焊在过渡层上熔覆YD557堆焊焊丝获得高硬层。通过优化熔覆工艺得到无裂纹、无气孔、成形良好的熔覆层。对获得的梯度过渡熔覆层进行组织分析、硬度和冲击韧性等测试。结果 基体-过渡层-高硬层两两之间产生了良好的冶金结合,熔覆层中无明显缺陷产生。微观形貌分析结果表明,在过渡层中有胞状晶与胞状枝晶产生,高硬层主要由板条马氏体组成。硬度测试结果表明,基体硬度为350HV,高硬层的平均硬度为620HV,过渡层平均硬度为480HV,过渡层硬度处于高硬层硬度与基板硬度之间,各部分硬度的梯度分布既提高了复合板的耐磨性,又增强了复合板的韧性。在冲击性能测试中,基体的平均冲击吸收功为34 J,复合板的平均冲击吸收功为68.48 J,为基体的2.5倍。在摩擦磨损实验中,基材的磨损质量为15.1 mg,而熔覆层的磨损质量仅为4.2 mg,基体的磨损质量为熔覆层的3.59倍;熔覆层平均摩擦因数为0.398 7,相较于基材的降低了0.072 8;熔覆层的磨损机制为磨粒磨损,基材的磨损机制为黏着磨损。结论 设计的复合梯度熔覆层既能提高表面的使用性能,又能增强熔覆层的韧性,减少裂纹的产生。     

Evaluation of rhenium carbide as a prospective material for hard coating

The literature reveals that interstitial alloys based on rhenium as a precursor might be extremely hard, becoming suitable to be used as hard coatings. In this work, we have produced rhenium carbide (ReC_x) films by the reactive pulsed laser deposition method. Nanoindentation has been performed to estimate hardness. The maximum hardness value for ReC_x films resulted to be 22.5 GPa. We found no evidence that ReC_x films have hardness, or plasticity, higher than competitive hard coating materials. Our results and the fact that rhenium is expensive and scarce, suggest that preceding reports are overoptimistic on the prospective use of rhenium carbide as hard coatings.     

Coolant pH control for optimum ceramic grinding Part II Influence of the rebinder effect on the surface grinding of aluminum oxide

Variations in the grinding (machining) properties of aluminum oxide attributable to the Rebinder effect, an environment-caused variation in the hardness of rock, ceramic, or glass, were investigated using conventional surface grinding equipment. Systematic variation in normal force, tangential force, roughness average, waviness average, and post grinding flexural strength were attributable to the grinding condition (coarse or fine) and the pH of the coolant. Observations in this study are consistent with a ductile/brittle grinding transition for fine grinding, a brittle/brittle grinding transition for coarse grinding and pH control of plastic deformation.     

离心铸造Mg2Si 和Si 自生增强锌基复合材料的组织与性能

采用热模金属型工艺, 离心铸造Zn-27Al-9.8Mg-5.2Si 和Zn-27Al-6.3Mg-3.7Si 合金, 获得了内层聚集大量块状初生Mg₂Si 、少量初生Si, 中层不含初生Mg₂Si 和初生Si, 外层含有初生Mg- Si 和初生Si 的自生锌基复合材料。离心铸造Zn-27Al-3.2Mg-1.8Si 合金, 获得了不含初生Mg₂Si 和初生Si 的单层材料。考察了复合材料的组织形貌, 检测了复合材料的硬度和耐磨性, 分析了复合材料的断裂模式。结果表明: 复合材料的内层因聚集大量的初生Mg₂Si 和初生Si 具有较高的硬度和较优的耐磨性。复合材料的断裂方式为脆性断裂, 含共晶Mg₂Si 和共晶Si 的中层在断裂中比含块状初生Mg₂Si 和初生Si 的内层经历了更多的塑性变形。      

Study of sulfur embrittlement in electroformed Ni-Re alloy

Although the amount of cathodic absorption sulfur (sulfur content) was enhanced by the presence of rhenium in electroformed nickel, superior ductility of the Ni-Re alloy deposits obtained from saccharin-free baths was determined, even when the deposits were treated at 400°C. On the other hand, owing to the presence of saccharin in the alloy baths changed the banded microstructure of the alloy deposit to granular microstructure after 400°C thermal treatment, resulting in sulfur embrittlement even the sulfur content was only about 100 ppm. Deposit microstructures, X-ray diffraction patterns, and ductility data were investigated to evaluate the effect of rhenium and saccharin on sulfur embrittlement in the alloy deposits. In addition, the effect of rhenium and sulfur on deposit hardness was also studied.     

钛氮合金的铸态组织与性能

采用熔铸工艺法制备了含氮量为0.045%～0.27%的原位自生氮化物增强钛基复合材料,分析并测试了合金的铸态组织和力学性能.研究结果表明:在Ti-N合金中,随着氮含量的增加,合金中氮化物的形态和相组成发生了明显的改变;当氮含量在0.045%～0.18%时,合金的基体为α-Ti,增强相为TiN0.3;氮含量增加到0.225%时,增强相转变为块状Ti2N;复合材料的硬度、抗压强度和弹性模量均高于纯钛基体且随着氮含量的增加而增加;当增强相由TiN0.3转变为Ti2N时,抗压强度显著增加;由压缩断口分析可知,基体为韧性断裂,随着氮含量增加合金由韧窝 解理断口向具有解理特征的脆性断裂转变.     

燃烧合成TiC-Ni材料的室温及高温力学性能

研究了燃烧合成新工艺制备的TiC-Ni金属陶瓷材料的力学性能。结果表明:TiC-Ni金属陶瓷硬度值和抗弯强度在Ni含量为20 wt%时达到最高值,断裂韧性在Ni含量为30 wt%时达到最大值,TiC-Ni材料在室温下具有无宏观塑性变形的脆性断裂特征。随着温度的升高,TiC-Ni材料弯曲强度下降,温度超过1000℃开始发生塑性变形。其强度与传统方法生产的相近成分材料相比比较接近。      

Nano-grained Net-Shaped Fabrication of Re Components by EB-PVD

Cost-effective net-shaped forming components have brought considerable interest into the Department of Defense, the National Aeronautics & Space Administration, and the Department of Energy. Electron beam-physical vapor deposition (EB-PVD) offers flexibility in forming net-shaped components with tailored microstructure and chemistry. High-purity rhenium components, including rhenium-coated graphite balls and rhenium plates and tubes, have been successfully manufactured by EB-PVD. EB-PVD rhenium components exhibited submicron and nano-size microstructure with high hardness and strength as compared with chemical vapor deposition (CVD). It is estimated that the cost of rhenium components manufactured by EB-PVD would be less than the current CVD and powder-high-temperature isostatic pressure technologies.