细晶粒钛合金焊接接头粗晶区的精细结构

采用透射电子显微镜,研究显微组织为等轴状结构的细晶粒Ti-6Al-4V合金在3种焊接参数作用下焊接接头粗晶区的精细结构,并测量接头显微硬度的分布.结果表明:粗晶区晶内初生α′马氏体随热输入增大显著粗化,其形态特征由针状长大成为板条状;在较大热输入下相互平行排列的α′马氏体板条束引起粗晶区强度和延展性下降;初生α′马氏体内部的亚结构以位错和堆垛层错为主,并存在少量孪晶,随热输入增大,位错密度增加;热输入增大也引起由残余β相转变生成的次生α′尺寸增大;3种焊接参数下的热影响区中均未出现软化现象.     

高温停留时间对细晶粒钛合金粗晶区组织的影响

采用热模拟试验方法,研究了高温停留时间对显微组织为等轴状结构的细晶粒Ti-6Al-4V合金热影响区粗晶区晶粒生长、微观组织转变和性能的影响.结果表明,较长的高温停留时间作用下,粗晶区晶粒严重粗化.晶内精细结构占主体的是相互交错排列的片状α'马氏体,其亚结构以孪晶为主;而随着高温停留时间的减少,粗晶区晶粒长大趋势减小,晶内α'马氏体呈板条状,板条内部存在高密度位错;粗晶区硬度随高温停留时间的增加而减小;较小的高温停留时间作用下,粗晶区具有更小的晶粒尺寸,其晶内位错马氏体束较细小,具有更好的综合力学性能.     

TC4钛合金激光焊接头微观组织和硬度

采用光学显微镜和场发射扫描电镜观察了TC4钛合金激光焊接接头的显微组织,测量了接头焊缝中心到母材的显微硬度。结果表明,母材由α相和其相界上断续分布的粒状β相组成。焊接接头组织由粗大等轴晶区、柱状晶区、细等轴晶区和热影响区过热组织组成。粗大等轴晶区组织形态有层片状α+β、魏氏体α和网篮状α+β3种,其显微硬度略低于柱状晶区和细等轴晶区,但比母材高;柱状晶区和细等轴晶区组织为针状马氏体,柱状晶区显微硬度相对较高。热影响区显微硬度与母材相差不大。     

工程机械用Ti-Nb高强度钢焊接接头的微观组织和力学性能研究

以Ti-Nb高强度钢为对象,研究微合金化过程中其焊接接头的微观组织和力学性能。结果表明,由于晶粒粗化、位错密度降低和变形强化作用减小,焊接后Ti-Nb高强度钢出现了软化现象。热影响区中,粗晶区和细晶区是焊接接头的软化区。随着焊接热输入的增加,焊接接头的软化程度增强。对其进行回火处理后,硬度和抗拉强度均逐渐提高。     

填充金属对TC4钛合金激光填丝焊接头组织性能影响

分别采用TC3实心焊丝和Ti-Al-V-Mo系药芯焊丝作为填充金属，进行TC4钛合金板窄间隙激光填丝焊，并对获得的焊接接头组织性能进行分析研究。结果表明，两组焊接接头各区域的微观尺度区别较明显，激光填药芯焊丝焊接接头中的焊缝区与粗晶区中的α’马氏体长度较小，并且焊缝区中原始β相晶界宽度也较窄；激光填实心焊丝焊缝中α’马氏体板条约为0.55μm，板条α’马氏体之间穿插着少量残留β相，在α’马氏体内部发现位错，并形成少量的位错塞积；激光填药芯焊丝焊缝中的针状α’马氏体宽度约为0.35μm，板条α’马氏体之间同样穿插着少量残留β相，针状α’马氏体内含有少量的细孪晶和大量的位错塞积形成的位错墙，同时在相界位置也发现更加密集的位错，残留β相含量也要略多；激光填实心焊丝焊接接头焊缝区中晶粒间的取向差大于10°的大角度晶界占比约79.25%，药芯焊丝约为96.27%；激光填药芯焊丝焊接接头的焊缝区及热影响区硬度平均值及拉伸性能数值均大于激光填实心焊丝的焊接接头。     

钛合金电子束深熔焊接头的组织及缺陷(英文)

对大厚度钛合金电子束焊接接头的显微组织、相组成和冷隔缺陷进行研究。结果表明,焊缝区组织为马氏体α′相;热影响区由细晶区和粗晶区两部分组成,细晶区组织为初生α相+β相+等轴α相,粗晶区组织为少量的初生α相+针状α′相;母材区组织基本上都是长条状和块状的初生α相,其间分布着少量残余β相。对冷隔的形成原因进行了分析,并提出了预防措施。     

基于改进Voronoi图法的焊接接头微观组织建模

为了从微观尺度研究焊接接头的疲劳裂纹萌生过程,对传统的Voronoi图法进行改进,建立了焊接接头焊缝区柱状晶及细、粗等轴晶混合晶区的微观组织模型.?首先依据金相试验结果将焊缝区划分不同微观区域,通过控制不同微区种子点的密度和位置生成等轴晶及柱状晶微观组织模型,再通过布尔运算合并微区,建立焊缝区混合晶区微观组织模型.?结...     

5086铝合金CMT焊接接头微观组织及力学性能研究

采用冷金属过渡焊接技术(CMT)对中低速磁悬浮列车用1 mm厚的5086 H32铝合金进行平板对接焊试验,对不同工艺下的接头进行微观组织观察和力学性能测试,并利用透射电镜(TEM)对接头不同微区中位错和沉淀相进行观察。结果表明:在焊接电流52~61 A,焊速60~90 cm/min的工艺下获得质量可靠的焊接接头;CMT焊接接头由焊缝区(WZ)、热影响区(HAZ)和母材组成,WZ由细小等轴晶和柱状晶组成,熔合线附近出现宽度约为100μm的细晶区;与母材相比,HAZ晶粒存在不同程度的减小;WZ显微硬度最低,HAZ次之;母材位错密度大,缠结严重,HAZ位错密度较低,WZ几乎没有位错;与沉淀相相比,位错密度对CMT接头不同微区的显微硬度影响较大。     

TC17钛合金惯性摩擦焊接头组织特征分析

TC17是一种α β型钛合金,主要用于制造航空发动机整体叶盘、转子和大截面锻件.采用惯性摩擦焊工艺制造航空发动机压气机整体转子能够减少零件数量并有效地提高结构刚度.主要分析TC17惯性摩擦焊接头区组织特征,结果表明:接头组织为细晶区、变形晶区和热影响区,晶粒内部为残留的亚稳定β'相;焊接接头时效热处理后晶粒内部为细小的层片束初生α相、短小的次生α相和β相.     

细晶粒钛合金粗晶区组织及接头力学性能分析

针对TIG焊接过程,研究了显微组织为层片状结构的细晶粒Ti-6Al-4V合金热影响区粗晶区组织转变规律,分析了热输入对粗晶区晶粒生长和接头力学性能的影响.粗晶区晶粒尺寸的测量结果显示,经历焊接热循环后,晶粒具有严重的长大倾向.焊接过程中,粗晶区发生了马氏体相变,形成α′马氏体组织.随着热输入的增加,粗晶区组织将由尺寸较小,且相互交错的α′丛,持续生长成贯穿整个晶粒的粗大α′束.硬度测量结果表明,热影响区中存在一个软化区间,该区间宽度随焊接热输入增加而增大.细晶粒Ti-6Al-4V合金焊接接头抗拉强度随热输入增加而减小.较大热输入下,断口位于粗晶区内,拉伸断口呈准解理断裂特征.     

大厚度TC21钛合金电子束焊接试验

对56mm厚TC21钛合金进行了电子束对接试验,对接头显微组织和力学性能进行了研究.结果表明,接头焊缝区组织形态以柱状β晶粒为基体,针状的马氏体弥散其中;热影响区从焊缝到母材分为三个区域,依次为等轴再结晶β晶粒区、片状和针状а相形成的魏氏组织区以及片状α相聚集长大的区域;熔合区内柱状晶与等轴晶联生.接头强度达到母材水平,断裂发生在母材内,接头厚度方向性能一致.接头塑性损失较大,只达到母材的50%左右.接头焊缝区硬度最高,其次是热影响区的等轴晶区和魏氏组织区,而热影响区内片状α相聚集长大的区域硬度值最低.

Abstract：

Electron beam welding of TC21 56 mm titanium alloy was carried out. The microstructure and the mechanical properties of welded joints were analyzed and tested. The results showed that the weld zone consisted of the columnar β gains, and in which the transgranular acicular α' martensite were dispersedly distributed. HAZ can be divided into three parts from base metal to weld zone, which are the equiaxed recrystallized β grain zone, Widmanstaten structure zone formed by lamellar and aeicular α phases and lamellar a phase coarsening zone. Fusion zone consists of the adnate columnar and equiaxed grains. Tensile strength of joints reaches to that of base metal and the failure appears in the base metal. The mechanical properties are uniform along the vertical direction. Plasticity in the welded joint is greatly decreased and only up to 50% of that of the base metal. The microhardness in weld zone is the highest, and that of the equiaxed grain zone and Widmanstaten structure zone in HAZ is higher, and the microhardness in columnar a phase coarsening zone is the lowest.     

Double-sided gas tungsten arc welding process on TC4 titanium alloy

TC4 titanium alloy was welded by double-sided gas tungsten arc welding（GTAW） process in comparison with conventional GTAW process, the microstructure and mechanical performance of weld were also studied. The results indicate that double-sided GTAW is superior over regular single-sided GTAW on the aspects of increasing penetration, reducing welding deformation and improving welding efficiency. Good weld joint was obtained, which can reach 96.14% tensile strength and 70.85% elongation percentage of the base metal. The grains in heat-affected zone（HAZ） are thin and equiaxed and the degree of grain coarsening increases as one moves to the weld center line, and the interior of grains are α and α′ structures. The coarse columned and equiaxed grains, which interlace martensitic structures α′ and acicular α structures, are observed in weld zone. The fracture mode is ductile fracture.     

TC4合金TIG焊接头组织转变与力学性能分析

针对TC4合金TIG焊接头微观组织特征以及焊接过程中的组织转变规律进行了研究,并对接头力学性能进行了分析.经历TIG焊接热循环之后,焊缝及热影响区粗晶区晶粒严重粗化,热影响区晶粒尺寸具有突变特征,过渡区组织呈带状分布,不存在明显的细晶区.升温过程中(α+β)→β转变过程包括两个阶段:原始β→高温β转变和原始α→高温β转变,而且在原始α→高温β转变开始之前,原始β→高温β转变已经完成.冷却过程中在β→α'转变区间冷速较慢时,α'相首先在高温β晶界上形核,并向晶内生长,生成针状α';在快速冷却时,α'相在晶内大量形核,形成"筐篮"组织.硬度测量结果表明,粗晶区部位存在一个软化区;接头抗拉强度与母材接近,接头性能优异.

Abstract：

The microstructure and phase transformation of TC4 alloy weld joints during TIG welding were investigated. The mechanical properties of the welded joints were also tested. When the TC4 alloy was heated by TIG arc, grains in the weld bead and heat affected zone (HAZ) were badly coarsening. The grain size in HAZ has mutant character. The microstructure in the transition region presented zonal distribution. There was no obvious fine grained region. In temperature-rise period, the transformation of (α + β)→β was divided into two processes which included the original β→ high-temperature β and the original α→ high-temperature β. And the previous phase transformation was finished before the next starting. In the cooling process, slowly cooling rate introduced α' phases nucleating at the high-temperature β grain boundary in the β→α transform temperature range. The α' martensite grew up into the center of the β grains and generated acicular martensite. With quicker cooling rate, large numbers of α' phase nucleated in the high-temperature β grains and generated orthogonally oriented martensites. Hardness measurements show there is a softened zone in HAZ. Tensile strength of welded joint was approximate with the base metal. And the properties of the welded joints were good.     

电子束焊接热输入对Ti-24Al-15Nb-1.5Mo/TC11双合金焊接接头组织和显微硬度的影响

利用OM,SEM,能谱分析和显微硬度等测试方法对Ti-24Al-15Nb-1.5Mo/TC11双合金焊接接头的显微组织特征及硬度进行了分析.结果表明,焊接热输人为135 kJ/m时,焊缝熔合区柱状晶由均匀密集的α'相针状马氏体和少量α相组成,显微硬度平均值为447 HV.焊接热输入增大到150 kJ/m时,熔合区α'相明显减少,焊缝TC11合金侧热影响区的短针状α+β组织变为粗大的长针状组织,Ti-24Al-15Nb-1.5Mo热影响区的β晶粒变得更粗,显微硬度平均值降为402 Hv.这主要是因为增大热输入使焊缝合金元素含量的比例发生变化,并且冷却速度下降使焊缝组织形态和分布改变,最终导致显微硬度降低.合金元素Ti,Al,Nb的含量在焊缝边界发生突变,但在焊缝熔合区达到一个新的平衡.

Abstract：

Microstructure evolution characterization of the Ti-24Al-15Nb-1.5Mo/TC11 dual alloys welded joints obtained on the condition of different electron beam heat input was studied by optical microscope, scanning electron microscope, energy spectrum and micro-hardness analysis. The results show that the energy input have an important effect on the microstructure, grain size, micro-hardness and alloy elements content of welded joints. The microstructure is made up of homogeneous acicular martensite α' phase in fusion zone (FZ) and the average micro-hardness value is 447HV when heat input E = 135 kJ/m is utilized. With heat input increasing to 150 kJ/ m, the number of α'phase decreases in FZ, short acicular α + β phase become coarser in heat-affected zone(HAZ) of TC11, coarse β grains become larger in HAZ of Ti-24Al-15Nb-1.5Mo and the average micro-hardness value drops to 402HV. The result is attributed to the changed content of alloy elements and lower cooling velocity caused by increasing heat input. The content of element Ti, Al and Nb is changed abruptly in the boundary of the joint, but these elements evenly distribute in each zone and hardly diffuse.     

X80管线钢及其接头的低温韧性和显微组织

分别利用示波冲击韧性试验、硬度试验和光学显微镜、透射电镜研究了X80管线钢及其焊管接头的力学性能和显微组织。试验结果表明，X80钢及其焊管接头具有良好的韧性，其中焊缝的韧性最高，焊接热影响区粗晶区因受焊接热效应引起晶粒粗化和形成脆性组织，故韧性最低。试验钢由针状铁素体和少量块状铁素体组成，焊缝为典型的针状铁素体组织，焊接热影响区粗晶区以粒状贝氏体为主。焊接热影响区熔合线附近的硬度值最高，越远离熔合线硬度值越低，并逐渐接近母材的硬度值。     

Microstructure of Laser-MAG Hybrid Welds of Sintered P/M Steel

The microstructure and mechanical properties of iron-based powder metallurgical steels jointed by CO₂ laser-metal active gas (MAG) hybrid welding were investigated. The cross-sectional morphology of hybrid weld bead consisted of arc zone and laser zone. The microstructure of arc zone consisted of columnar dendrite and fine acicular dendrite between the columnar dendrites, but that of laser zone was composed of fine equiaxed dendrite. The MAG weld had obvious heat-affected zone (HAZ) zone, while hybrid weld had very narrow HAZ zone because of the rapid cooling rate. The phase constitutions of the joint determined by x-ray diffraction were α-Fe (ferrite) and Cu. The 2θ value of α-Fe (200) peaks of hybrid weld was smaller than that of sintering compact. Compared to MAG weld, hybrid weld had finer grain size, higher micro-hardness, and higher micro-strain, which was caused by the difference of cooling rate and crystallizing.     

X80管线钢热丝TIG焊接接头显微组织和力学性能

采用热丝TIG焊对X80钢板进行对接,并研究了接头的显微组织和力学性能。结果表明:焊缝区主要为针状铁素体(AF)组织,热影响区粗晶区主要为贝氏体铁素体(BF)和粒状贝氏体(GB)组织,细晶区主要是多边形铁素体(PF)和少量贝氏体组成;焊接接头的平均抗拉强度为643 MPa,断裂在母材区;在-30℃时焊缝区的冲击吸收功高于热影响区,焊缝主要是韧脆混合断裂为主,而HAZ主要以脆性断裂为主。焊缝区的硬度较高,焊接接头HAZ存在硬化和软化现象。     

Characteristics of 5A90 Aluminum-lithium Alloy by YAG-MIG Hybrid Welding

The characteristics of 5A90 Aluminum-Lithium alloy by YAG laser and MIG arc hybrid welding (Hybrid welding) were studied.Compared with the laser beam welding (LBW),the hybrid welding could not only improve the weld appearance significantly,but also have better engineering compatibility.The obvious microstructure characteristics of joint by the hybrid welding are fine-grained layer near fusion-line and the equiaxed grain in most area of welded seam.The subgrains of the equiaxed grains,located in the weld center,tend to coarse from bottom to top of weld joint.The microhardness of welded seam by the hybrid welding (83.57HV0.2) is lower than that by LBW (95.65HV0.2),but the uniformity of the former is better than that of the latter.The ultimate strength and the elongations after fracture of the joint by the hybrid welding are lower than that by LBW.The tensile fracture always occurs in HAZ or weld centerline,and the fractography presents mixture rupture.Therefore,if the combined mechanical properties of joint by the hybrid welding meet the operation requirements,it should be improved by reasonable artificial aging or heat treatment after welding,and it also should develop a better filler wire matched with the base metal.     

因瓦合金4J36等离子焊接工艺及接头性能

试验采用等离子弧焊设备对4J36因瓦合金板材进行焊接工艺试验,借助光学显微镜(OM)、扫描电镜(SEM)、能谱分析仪(EDS)、X射线衍射仪(XRD)和洛氏硬度计等手段分析接头的微观组织和力学性能.结果表明,合理的等离子工艺参数下焊接接头成形良好,抗拉强度可达到母材的93.6%;接头基体为γ相,同时存在γ'(Ni₃(Al,Ti))强化相;母材为细小的等轴晶,焊缝处呈树枝状结晶且晶粒粗大,热影响区靠近熔池部分的晶粒过热长大,靠近母材部分为均匀细小的等轴晶;焊接接头拉伸断口表现为韧性断裂,硬度最低值出现在热影响区.