Ti3Al合金激光焊接接头高温拉伸性能及显微组织

研究Ti-24Al-17Nb合金激光焊接接头的室温及高温拉伸性能,并分析接头显微组织和拉伸断口。研究结果表明,室温下焊缝为单一β/B2相柱状晶组织,室温横向拉伸时接头强度与母材强度相当、塑性有所下降、但仍有25%左右的伸长率,断裂大部分发生在母材部位、少部分断裂在焊缝;高温拉伸时断裂均发生在焊缝部位。高温拉伸时,接头组织发生变化,α2相和B2相向O相转变;焊缝β/B2相向O相转变的切变相变,使原来柱状晶晶界应变集中、容易产生微裂纹,使接头高温强度和塑性明显降低,高温拉伸断口呈现沿晶断裂和解理断裂的脆性断裂形式。     

激光焊接热输入对Ti2AlNb合金组织性能的影响

研究激光焊接热输入对Ti-22Al-27Nb(at%)合金焊缝成形和力学性能的影响,利用OM、SEM、XRD和TEM等手段对焊接接头的显微组织特征进行了分析,并探讨了焊后热处理对焊接接头组织性能的影响。结果表明,连续激光焊接可以获得无缺陷、成形良好的焊接接头。焊缝区域组织主要为柱状的B2相,柱状晶的生长方向垂直于熔合线。焊缝和热影响区的显微硬度要高于母材,焊缝的平均显微硬度最高。随着热输入的增加,焊接接头的室温抗拉强度增加,但是焊接接头的延伸率较低。焊接接头650℃高温强度为母材的71%~75%,塑性则仅为母材塑性的40%左右。经过焊后热处理,焊缝由B2+O相组成。O相增多使得焊缝的室温强度略有提高,且提高了650℃高温拉伸性能,高温抗拉强度最高可达母材的87.5%。     

焊后热处理对Ti-22Al-27Nb合金激光焊接接头组织与高温性能的影响

研究焊后热处理对激光焊接2.5 mm厚Ti-22Al-27Nb合金组织和高温力学性能的影响。结果表明,Ti-22Al-27Nb合金激光焊接焊缝组织为单一的B2相。焊缝650℃高温抗拉强度为母材的75%,塑性则仅为母材塑性的40%左右。拉伸断口形貌为岩石状,呈现沿晶断裂特征。经过焊后热处理,焊缝组织为B2相+O相。相对于未热处理接头,热处理后焊缝和热影响区的硬度下降很多并趋于平缓。热处理温度750℃、保温时间1 h时焊接接头650℃高温抗拉强度达到了母材的87.5%,塑性为母材的82.2%,接头断裂形式为解理断裂。     

Ti-23Al-17Nb激光焊接接头的组织性能研究

通过室温和高温拉伸性能测试研究焊后热处理和同步预热对Ti-23Al-17Nb(原子分数,下同)合金CO_2激光焊接接头性能的影响.结果表明,接头室温和高温拉伸性能低,焊后真空热处理提高接头室温和高温拉伸性能,仍低于母材;同步预热接头室温强度和塑性与母材相当,高温强度与焊后热处理效果相当.组织分析显示,焊缝存在两个腐蚀衬度区,组织为B2相,热影响区晶粒由熔合线到母材逐渐细化,焊后热处理和同步预热改变β相基体上α2相的析出.     

高温钛合金Ti-55与Ti-60电子束焊接头力学性能

通过研究异种材料高温钛合金Ti-55与Ti-60电子束对接焊接头的微观组织和拉伸力学性能以及焊后热处理对Ti-60接头高温拉伸与持久性能的影响,分析电子束焊接高温钛合金的适用性.采用所选择的电子束焊接工艺焊接高温钛合金,焊缝成形好,表面缺陷少.分别进行了Ti-55,Ti-60,Ti-55+Ti-60焊接接头的室温、高温...     

Ti17合金电子束焊接接头的力学性能

通过室温拉伸试验、室温缺口拉伸、室温冲击试验以及金相分析对Ti17合金电子束焊接接头的显微组织和室温力学性能进行了研究.试验结果表明:用电子束焊方法焊接Ti17合金可获得室温性能良好的焊接接头,其接头的抗拉强度不低于母材,焊缝的缺口敏感系数均小于1,焊缝具有较高的冲击韧度.焊缝区组织与母材组织基本相同,都是α相上分布着沿晶界及晶内析出的细针状β相,焊缝区的晶粒度要比母材的晶粒度粗大.     

扫描预热对Ti2AlNb电子束接头组织及拉伸性能影响

采用电子束扫描对Ti-22Al-24Nb-0.5Mo合金进行了250～550℃的预热及电子束焊接工艺试验,利用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)等对接头显微组织特征进行了分析,分析了不同预热温度下焊缝的组织形貌,研究了预热对接头成形及其室温、高温拉伸性能的影响.结果表明,随着预热温度升高,焊缝中心等轴晶组织比例相应增加,焊缝中心结合线随之消失,柱状晶组织生长受到阻碍,这可能是横向温度梯度降低,结晶潜热无法被及时传导造成的.预热焊接接头室温抗拉强度、断后伸长率可达980 MPa、12％以上,与母材水平相当;与常规焊接相比,预热接头650℃拉伸强度提高了35％～60％,断后伸长率提高了两倍以上,350℃预热接头高温拉伸强度最高.接头拉伸性能的改善,与预热工艺对焊缝中心结合线、焊缝组织均匀性的影响密切相关.     

Ti3Al激光焊接接头组织与织构的EBSD分析

采用电子背散射衍射(EBSD)技术对Ti-23A1-17Nb合金CO2激光焊接接头的焊缝、热影响区和母材的组织组成、晶粒大小及形态、晶粒取向和取向差分布进行了研究.结果表明,焊接接头中焊缝和热影响区的组织是B2相,母材由B2相和少量的α2相组成.从母材、热影响区到焊缝,晶粒尺寸依次增大,母材为细小等轴晶,母材内B2相尺...     

GH625合金氩弧焊焊接接头的疲劳裂纹扩展性能

研究了钨极氩弧焊GH625高温合金焊接接头的室温疲劳裂纹扩展行为。采用金相显微镜及扫描电镜对其焊接接头的显微组织和疲劳裂纹扩展断口形貌进行观察。结果表明,GH625高温合金的钨极氩弧焊焊接接头主要是由枝晶状焊缝组织和γ奥氏体等轴晶母材组成,焊缝区析出大量的白色针状δ-Ni3Nb相和块状颗粒状Laves相;其焊接接头的显微硬度高于母材;室温下,在低ΔK区间,GH625高温合金钨极氩弧焊焊接接头的疲劳裂纹扩展速率比母材低,这是由于焊缝处硬质的析出相、二次裂纹以及扩展路径的曲折多样使得其裂纹扩展时需要消耗更多的能量;在高ΔK区间内,焊接接头疲劳裂纹扩展速率高于母材。     

转向架用耐候钢焊接接头显微组织和力学性能

以转向架用国产耐候钢S355J2W与进口耐候钢SMA490BW为研究对象,选用进口焊丝G424M21Z与国产焊丝CHW-55CNH进行焊接,获得3种焊接接头。通过金相、硬度、拉伸和弯曲试验,对接头进行显微组织和力学性能研究。结果表明,3种接头的基本力学性均能满足标准要求;1#、2#接头焊缝区硬度比母材区高,拉伸断裂位置在母材处,为高配焊丝;3#接头焊缝区硬度和母材区相当,拉伸断裂在焊缝处,其抗拉强度比1#、2#高,但延伸率及塑性较差,为低配焊丝。     

Influence of Filler on the Microstructure,Mechanical Properties and Residual Stresses in TIG Weldments of Dissimilar Titanium Alloys

The influence of titanium alloy (Ti-5Al-2.5Sn) and commercially pure titanium (cpTi) as fillers on dissimilar pulsed tungsten inert gas weldments of Ti-5Al-2.5Sn/cpTi was investigated in terms of microstructure,mechanical/nano-mechanical proper-ties,and residual stresses.A partial martensitic transformation was observed in the weldments for all the welding conditions due to high heat input.The microstructure evolved in the FZ/cpTi interfacial region was observed to be the most sensitive to the proportion of α stabilizer in the filler alloy.Furthermore,the addition of filler alloy improved the tensile properties and nano-mechanical response of the weld joint owing to the increased volume of metal in the weld joint.As compared to the Ti-5Al-2.5Sn wire,the use of cpTi filler wire proved to be better in terms of energy absorbed during tensile and impact tests,tensile strength and ductility of the dissimilar welds.An asymmetrical residual stresses profile was observed close to the weld centerline,with high compressive stresses on the Ti-5Al-2.5Sn side for both the weldments obtained with and without filler wires.This was attributed to mainly the low thermal conductivity of Ti-5Al-2.5Sn.The presence of residual stresses also influenced the nano-hardness profile across the weldments.     

Tensile properties and fracture toughness of 18Ni (250 grade) maraging steel weldments

Abstract

Gas tungsten arc welding was performed on 18Ni (250 grade) maraging steel sheet using two different filler wires: one of the same composition as the base material and the other containing more cobalt and aluminium and less molybdenum and titanium. Weld specimens were then aged under four different sets of conditions. After metallographic characterisation, mechanical properties including hardness, tensile strength and ductility, and fracture toughness were evaluated. Results showed that use of the matching filler material led to lower strength but higher ductility than in the other case; this was attributed to the presence of reverted austenite in the former (caused by segregation, especially of molybdenum) at the fusion zone substructure boundaries. In both types of weld metal, a re-solution treatment followed by aging at 480°C resulted in optimum tensile properties. Fracture toughness of the aged weldments was in general close to that of the parent material aged at 480°C; some deterioration occurred only when welds with pronounced segregation were made at high temperature.     

Cr5Mo钢管及其焊接接头长期服役后的组织性能与剩余寿命

本文研究了炼油厂铂重整装置临氢系统Cr5Mo耐热钢管及其焊接接头长期服役后的显微组织、力学性能和剩余寿命。试验结果表明,母材的组织和性能变化较小,估计还可继续使用10万小时。焊接热影响区的过热区已由马氏体转变为回火屈氏体,熔合线焊缝侧的类马氏体也已发生了回火,并在熔合线附近出现了增碳层。焊接接头的室温和高温瞬时强度高于母材,但其塑性韧性均较低,是裂纹萌生和扩展的薄弱部位,需加强运行监督。     

Laser welding of 3 mm thick laser-cut AISI 304 stainless steel sheet

The objective of the present work was to study the laser weldability of laser-cut 3 mm thick AISI 304 austenitic stainless steel sheet (using oxygen as an assist gas). For minimizing heat input during laser cutting, which is an important factor influencing the thickness of the oxide layer on the cut surface, laser cutting was performed in pulsed mode. The results of the study demonstrated that although the laser welding of laser-cut specimens did not result in the formation of weld defects, the resultant laser weldments exhibited reduced ductility with respect to base metal and bead-on-plate laser weldments. Laser-cut and laser-welded specimens also displayed higher notch sensitivity than the base metal. However, laser-cut and laser-welded specimens still possessed enough ductility to pass guided bend tests.     

Ti / Al TIG微熔钎焊界面行为及接头断裂行为

以TIG电弧为热源,AlSi5焊丝为填充材料,采用SEM、EDS、XRD对Ti-6Al-4V(TC4)钛合金和AlMg6铝合金异种材料TIG微熔钎焊的接头、温度场以及断裂行为进行了研究。试验表明:焊接接头铝母材侧具备TIG填丝熔化焊特征,Ti母材处为钎焊特征。峰值温度的升高能够增加界面层厚度,峰值温度升高,界面层组织趋于复杂。降低高温停留时间能够减小界面层厚度,但随着峰值温度增加,过快的冷却速度会产生较大的内应力,形成贯穿界面的裂纹。钛/铝TIG微熔钎焊的断裂,铝侧发生的断裂是韧性+脆性的混合型断裂,气孔及微裂纹为断裂起源。钛合金的母材过量溶解或者熔化,会导致气孔直径增加,应严格控制热输入量及钛母材的熔化。     

Properties of titanium alloy AT2 and weldments of the alloy

Conclusions Alloy AT2 and weldments of the alloy have high strength and ductility at temperatures from 500 to –253°. The deformability of the weld seam is approximately the same as that of the alloy. The corrosion resistance in hydrochloric and phosphoric acids is the same for the weld seam and the base metal. Alloy AT2 and weldments of the alloy are more resistant to hydrochloric and phosphoric acids than alloy VT1.E. O. Paton Institute of Electric Welding of the Academy of Sciences, Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 66–68, January, 1976.     

Microstructure and mechanical properties of GTA weldments of titanium matrix composites prepared with or without current pulsing

The effects of current pulsing on the microstructure, hardness and tensile properties at different temperatures of gas tungsten arc (GTA) weldments of titanium matrix composites were studied. Full-penetration butt joints were made with or without current pulsing. Optical microscopy, hardness test and scanning electron microscopy were employed to evaluate the metallurgical characteristics of welded joints. Tensile properties of weldments at different temperatures were studied and correlated with the microstructure. The results exhibit that current pulsing leads to the refinement of the weld microstructure and TiB whisker and the redistribution of reinforcements resulting in higher hardness, tensile strength and ductility of weldments in the as-welded condition.     

Effect of post-weld heat treatment on microstructure and properties of Ti-23Al-17Nb alloy laser beam welding joints

The mechanical properties of Ti-23Al-17Nb (mole fraction,%) laser beam welding alloy joint at room temperature are comparable to that of the base materials.However,the strength and ductility of the as-welded joint deteriorate seriously after high temperature circulation.The effect of post-welded heat treatment on the microstructure and mechanical properties of the joint was investigated.The heat treatment was taken at 980 ℃ for 1.5 h,then furnace cooling and air cooling were performed separately.The results indicate that proper post-welded heat treatment improves the ductility of the joint at high temperature.     

Postweld solution annealing effects on the ductility of ni-co-cr-base alloy gas tungsten arc welds

The welding characteristics of a commercial wrought alloy with a nominal composition of Ni-29Co-28Cr-2.75Si were investigated. Gas tungsten arc weldments with filler metal matching the chemistry of the alloy were found to have limited room-temperature ductility in the as-welded condition. Since welding is the main fabrication method of this alloy, the welding and postweld heat treatment (PWHT) characteristics were examined to provide guidelines for fabrication in the field. Metallographic evaluation revealed that the weld metal was characterized by the distribution of a continuous eutectic phase consisting primarily of (Si,Ti)_xNi_y The continuous eutectic phase in the as-welded deposit, which caused poor ductility of the welds, was successfully reduced or removed with proper PWHT. The PWHT is necessary if cold forming of a weldment is required after welding or if adequate joint ductility is a design requirement. The recommended PWHT temperature is 1050 °C.