灰口铸铁焊接区氢的微观分布及逸出特点

采用显微镜下摄影测氢法,从微观上研究了灰口铸铁母材同质焊缝及异质焊缝焊接区扩散氢的分布及其逸出动态过程,说明了由于石墨的储氢及阻碍氢向前扩散的作用,使进入灰口铸铁焊接接头热影响区的扩散氢很少,因此,氢对灰口铸铁热影响区的冷裂纹倾向影响也小。     

灰铸铁异质焊条焊接时HAZ冷裂纹研究

综合采用插销试验、扩散氢测定和热模拟试验,研究了扩散氢与显微组织变化对灰铸铁焊接接头热影响区（ＨＡＺ）冷裂纹倾向的影响规律。结果表明,ＨＡＺ组织转变对冷裂纹倾向影响较大而对扩散氢影响较小,ＨＡＺ快冷造成的粗大高碳马氏体组织是导致ＨＡＺ冷裂纹倾向增大的主要原因。     

Microstructural features and properties of plasma sprayed YPSZ／NiCrAIY thermal barrier coating （TBC）

The plasma sprayed thermal barrier coating (TBC) consists of NiCrAlY bond coating and yttria partially stabilized zirconia (YPSZ) top coating. NiCrAlY coating mainly contains Ni solid solution with face centered cubic lattice, Al2 O3 oxides and pores. The most obvious feature of YPSZ coating with tetragonal zirconia is a lot of vertical microcracks in this coating. The thermal insulation capability of the TBC increased with an increase in YPSZ coating thickness, the temperature drop across the TBC increasing from 60℃ to 92℃ with increasing YPSZ coating thickness from 100 μm to 500 μm. The thermalshock resistance of the TBC decreased with increasing YPSZ coating thickness and cracks initiated mainly in original vertical microcrack tips of the YPSZ coating and propagated not only along YPSZ coating / NiCrAlY coating interface but also through NiCrAlY coating. The oxidation process of the TBC at 1 200℃ can be divided into two stages: traasieat oxidation stage with rapid oxidation rate and steady oxidation stage with slow oxidation. Their transition time was about 10 hours. The weight gain for 100 hours was 3. 222 mg/mm^2. It is favorable to increase YPSZ coating toughness and to decrease the pores and oxides of the TBC system for improving thermal shock resistance and oxidation resistance of the TBC.     

构建国际高级焊接技术人才的培训平台

分析了我国高等学校开展国际焊接培训的意义和优势;讨论了国际焊接工程师培训体系与我国高校现行焊接技术人才培养模式的互补性.     

Formation process, microstructure and mechanical property of transient liquid phase bonded aluminium-based metal matrix composite joint

1　INTRODUCTIONThealuminium basedmetalmatrixcomposites(MMCs)areadvancedmaterialsthathavesuperiorproperties ,especiallyincreasedstiffness ,highstrength ,goodwearresistanceandsuperiorelevatedtemperatureproperties .Theyhavereceivedconsider ableattentionascandidatesforadvancedindustrialapplications[1,2 ] .But ,theirapplicationshavebeenseverelyrestrictedbythelackofasuitablejoiningmethod[3] .AlthougthfusionweldingmethodscanbeusedtojointheMMCs ,themethodsnormallytendtoresultinunfavourablejoint…     

Bi、Ag对Sn-Zn无铅钎料性能与组织的影响

研究了Bi、Ag对Sn-9Zn无铅钎料系统润湿性、接头力学性能及微观组织的影响。结果表明:Sn-9Zn无铅钎料的润湿性较差,添加适量的Bi有助于提高钎料的润湿性和接头剪切强度,但同时也使接头的塑性降低;添加适量的Ag能明显改善钎料的润湿性和接头塑性,但Ag的质量分数超过1.5%时会降低钎料润湿性和接头剪切强度。Sn-9Zn-Bi系无铅钎料组织由富Sn相、富Zn相及Bi的析出物组成;Sn-9Zn-Ag系无铅钎料组织由富Sn相、富Zn相及AgZn3化合物组成。     

Features of microstructure and fracture in the transient liquid phase bonded aluminium-based metal matrix composite joints

Transient liquid phase (TLP) bonded aluminium-based metal matrix composite (MMC) joints can be classified into three distinct regions, i.e. the particulate segregation region, the denuded particulate region and the base material region. The microstracture of the particulate segregation region consists of alumina particulate and Al alloy matrix with the Al2 Cu and MgA12 04. It contains more and smaller alumina particalates compared with the base material region. The TLP bonded joints have the tensile strength of lSO MPa -200 MPa and the shear strength of 70 MPa ~ 100 MPa. With increasing tensile stress, cracks initiate in the particulate segregation region, especially in the particulate/particulate inter.face and the particulate/matrix integCace, and propagate along particulate/matrix integCace, througth thin matrix metal and by linking up the close cracks. The particulate segregation region is the weakest during tensile testing and shear testing due to obviously increased proportion of weak bonds (particulate-particulate bond and particulate-matrix bond).     

奥-贝球铁焊缝金属的连续冷却转变图及其组织分析

为了研究焊态下奥－贝球铁焊缝在不同冷速下的组织变化及其相变规律,本文采用Ｆｏｍａｓｔｏｎ－Ｆ相变分析仪测定了在不同冷速下焊缝金属的膨胀量曲线,然后通过对曲线特征进行分析,并结合金相组织定量分析及硬度分析等方法,找到了在各冷速下的相变临界点,最终建立了奥－贝球铁焊缝的连续冷却转变图（ＣＣＴ图）,为选择焊接工艺提供了科学的基础。     

激光熔覆参数对灰铸铁激光熔覆层裂纹的影响

通过调整激光熔覆工艺参数 ,对灰铸铁激光熔覆层裂纹问题的研究 ,发现表层裂纹率随激光扫描速度或激光功率的增加有最低值。结合激光熔覆工艺参数 ,分析了残余拉伸应力的变化 ,熔覆层树状晶的结晶方向及渗碳体组织长度和粗细程度的改变 ,同时也分析了珠光体的形态及分布与离异共晶的有无 ,解析了不同激光熔覆工艺参数形成不同裂纹率的原因。