EH36船板钢埋弧焊接头的组织和力学性能

采用埋弧焊工艺对EH36船板钢进行多道次、大热输入条件下的焊接试验,研究了焊接接头的显微组织和力学性能。结果表明:在大热输入条件下,焊缝组织由晶界铁素体、块状铁素体和少量针状铁素体组成,不存在侧板条铁素体,这对焊缝的力学性能有利;粗晶热影响区是受焊接热输入影响最严重的区域,冲击韧性最差的区域为焊缝;焊接接头的最高硬度出现在粗晶区靠近熔合线处,为222HV,最低硬度出现在细晶区,为181HV,未出现焊接软化区。     

不同热输入对TC4钛合金激光焊焊缝形貌和性能的影响

采用激光器YLS-10000型光纤激光器进行试验焊接5mm厚的TC_4钛合金,研究不同热输入变化对焊接接头形貌以,微观显微组织、显微硬度的影响。试验结果表明:TC_4钛合金焊缝具有三种截面形貌,分别为漏斗形和酒杯形、双曲线形,在热输入超过72J/mm后,能够将焊缝充分焊透。热输入不一样,焊接组织具有一致性,焊缝组织为针状马氏体α′,没有发现新相,热影响区硬度发生突变具有软化区。原因是冷却期间焊缝区将存在α′,焊缝区α′比热影响区的数量要多,故接头硬度值先降低后升高,不同热输入下焊接接头整体硬度高于母材,随着热输入的增加焊缝的平均硬度增加且软化区向母材移动。     

AZ31B镁合金搅拌摩擦焊接头的显微组织及耐腐蚀性能

对AZ31B镁合金板进行了搅拌摩擦焊,研究了焊接接头的显微组织、物相组成、硬度及耐腐蚀性能。结果表明:该接头焊核区为细小均匀的等轴晶,热机械影响区晶粒得到细化但沿金属塑性流动方向被拉长,热影响区的显微组织与母材区的比较接近,但其晶粒略粗大;与接头母材区相比,焊缝的物相组成未发生变化,各区的硬度有所降低且硬度随距焊缝中心距离的增加呈先减小后增大的变化趋势,硬度最低处位于热机械影响区内;接头的耐腐蚀性能略低于母材的,浸泡腐蚀后接头表面发生全面腐蚀,但各区域的腐蚀程度并不相同,热机械影响区的腐蚀最严重。     

T91钢瞬时液相扩散焊热影响区的组织及力学性能

模拟瞬时液相扩散焊三温工艺对T91钢进行焊接,并进行了780℃×2h回火处理,研究了热影响区的组织和力学性能以及回火处理对热影响区力学性能的影响。结果表明:热影响区可分为距焊缝0～7.5mm处的过热粗大板条马氏体区、距焊缝7.5～22.5mm处的细小板条马氏体区、距焊缝22.5～37.5mm处的铁素体+马氏体区以及距焊缝37.5～42.5mm处的回火马氏体区等4个区域;随着距焊缝距离的增大,热影响区的脆硬倾向降低,断裂机制由脆性断裂向韧性断裂转变;回火处理后热影响区的抗拉强度和硬度相比回火处理前的有所降低,但韧性提高。     

6061铝合金激光填丝焊接接头的组织与力学性能

通过显微硬度计、拉伸试验机、扫描电镜和X射线衍射仪等研究了激光填丝焊接6mm厚6061铝合金接头的显微组织和力学性能。结果表明:焊缝中心区域的显微组织为等轴晶,由α-Al固溶体组成,无β(Mg_2Si)强化相析出,近熔合区的焊缝组织为柱状晶;焊接接头焊缝的硬度最低,约为73HV,母材的硬度最高,约为110HV,随着距焊缝中心距离的增大,热影响区的硬度先呈波浪式增大,在距焊缝中心2.2~3.8 mm处有所下降,此外为热影响区软化区,在距焊缝中心3.8~4.4mm处又快速增大;焊接接头的抗拉强度为234 MPa,约为母材的71%,高于熔化极惰性气体保护焊接接头的;焊接接头均在焊缝处断裂,接头与母材均为韧性断裂。     

热处理对2205双相不锈钢焊接接头力学性能的影响

对手工焊接2205双相不锈钢接头进行1 050℃固溶处理,随后在850℃进行不同保温时间的时效处理,采用光学显微镜观察不同热处理状态下接头各区域组织演变特征及σ相的分布情况,利用硬度仪、拉伸和冲击试验机对焊接接头进行力学性能试验,并借助扫描电镜分析冲击断口形貌与断裂机制。结果表明,焊后1 050℃固溶处理可有效改善2205双相不锈钢焊接接头的组织和性能;在850℃时效处理后,母材区、焊缝区和热影响区均有σ相沿铁素体与奥氏体晶界析出,随着时效时间的延长,σ相向铁素体内部长大,且含量增加,其中焊缝区对σ相的析出行为最为敏感;接头各区域中σ相的析出使母材区和焊缝区的硬度值增加明显,且焊缝区的硬度增长较快;焊接接头的抗拉强度由于脆性σ相的析出有所提高,但塑性和冲击韧度显著下降;冲击断口的断裂机制由固溶态的混合断裂向时效处理后以解理断裂为特征的脆性断裂转变。     

热处理工艺对Ti2AlNb惯性摩擦焊接头组织及性能的影响

针对Ti_2AlNb合金惯性摩擦焊接接头开展了热处理工艺试验研究,分析了不同热处理工艺对焊接接头组织及力学性能的影响。研究表明,固溶态母材由α2、B2和O相构成,α2相呈球状或块状分布于B2相晶界上,O相呈棒状平行或交叉分布于B2相晶粒内部;固溶+单时效态合金母材由B2+O两相组成。焊态下的接头焊缝区及热力影响区基本为B2相组织,双时效处理后大部分B2相转变成晶界网状O相+晶内针状及块状O相组织,单时效处理的接头焊缝区及热力影响区晶界基本无O相组织存在,B2相晶内转变为细密层片状B2+O相共析组织。三种热处理状态的接头各区域显微硬度分布基本一致,焊后双时效提高了O相组织的析出而起到强化作用并提高了接头的显微硬度。焊前为固溶态+焊后双时效处理的接头室温抗拉强度最高且为1 193 MPa;焊后双时效处理的接头室温拉伸断口以准解理断裂为主,焊后单时效处理的接头室温拉伸断口以解理断裂为主,且解理小平面尺寸较大,抗拉强度稍低。焊前为固溶态+焊后双时效处理的接头在650℃高温下的抗拉强度依然最高且为986MPa,断口上能够观察到较浅的韧窝,为沿晶的韧性断裂;焊前为固溶态+时效处理的接头断口形貌基本相同,接头断裂形式以解理断裂为主,并含有少量的准解理断口。     

焊前预热对T2紫铜激光焊接接头组织和性能的影响

对2mm厚T2紫铜板进行了未预热和不同温度预热(100,150,200℃)的光纤激光焊接,研究了焊前预热对该焊接接头组织和性能的影响。结果表明:与未预热的相比,150℃预热激光焊接接头的熔深和熔宽较大,焊缝的等轴晶和熔合区的胞状晶粒均较粗大;预热激光焊接接头焊缝的电阻率与未预热的相比有所降低,焊前预热改善了焊接接头的导电性能;150℃预热激光焊接接头的显微硬度总体上高于100,200℃预热的,显微硬度均随距焊缝中心距离的增大先减后增,焊缝中心的最大;随着预热温度的升高,焊缝的自腐蚀电流密度先增大后减小,耐腐蚀性能虽先减小后增大,但相差较小。     

TC4钛合金等离子弧焊接接头组织及性能

采用等离子弧焊接工艺焊接TC4钛合金,通过室温拉伸、显微硬度测试、金相分析及X射线衍射试验,对TC4钛合金等离子弧焊接接头的显微组织和性能进行了研究。实验结果表明:TC4钛合金等离子弧焊接接头焊缝的组织为针状马氏体α'相和残余β相,组织形态为粗大柱状晶,过渡区和近焊缝区中的组织为细小的针状α相和β相、少量的α'相,组织形态为较粗大的等轴晶;接头焊缝熔化区的硬度最高;接头断口的主要微观特征为韧窝,属于延性断裂,但部分区域韧窝很浅,趋向于脆性断裂。     

2219铝合金双轴肩搅拌摩擦焊工艺及接头组织性能研究

通过对8mm厚2219铝合金进行双轴肩搅拌摩擦焊试验,研究了不同焊接速度对接头成形、组织演变及其对力学性能的影响规律。工艺试验结果表明:在固定转速(200r/min)下,不同焊接速度下的接头均成形良好,未出现微裂纹、隧道以及疏松等焊缝表面缺陷。随着焊接速度的增加,接头区域晶粒尺寸减小;接头显微硬度受到晶粒尺寸与沉淀相分布的制约,硬度分布曲线呈“W”形,热影响区硬度最低。并且随着焊接速度的增加,接头最低硬度和抗拉强度逐渐提高,断裂位置发生在热影响区与热影响区交界处。在焊接速度为350mm/min时,接头抗拉强度达到最大值335MPa,约为母材的72.8%。     

热处理对TC11/LF6异种金属摩擦焊质量的影响

对TC11/LF6钛铝异种金属进行了连续驱动摩擦焊接工艺及其焊后热处理工艺的研究,观察了热处理前后焊接接头焊合区微观组织并测定了试样力学性能。研究结果表明：未经热处理的焊接接头晶粒较为粗大,有明显的晶间化合物产生,接头显微硬度较高;经280℃退火1h后,焊接接头晶粒均匀细化,焊接界面产生较薄的不连续扩散层;热处理后接头晶粒明显细化,抗弯强度提高10.7%,显微硬度下降38%。通过组织和力学性能综合分析,得到最优化的TC11/LF6连续驱动摩擦焊接工艺参数。     

12Cr2Mo1R钢焊条电弧焊焊接接头的性能

采用焊条电弧焊工艺用奥氏体A302焊条对12Cr2Mo1R钢进行焊接,焊后对焊接接头进行425℃保温370h的热处理;对焊接接头进行了显微组织观察、能谱分析、物相测定和高温拉伸、冲击试验。结果表明:焊缝区组织为奥氏体、δ铁素体和少量碳化物;焊接接头高温拉伸屈服强度比母材的大,焊缝区的冲击功比母材的低;在焊缝区产生了少量脆性碳化物(M23C6型)和铁-铬新相,造成焊缝区的脆性比母材的增大。     

铝合金/黄铜异种金属电弧熔钎焊

采用Zn-15%Al实芯焊丝开展了铝合金/黄铜TIG熔钎焊搭接试验,并对接头力学性能、显微组织和界面层成分进行了测试分析。测试结果发现,焊态下,接头抗拉强度为164MPa;热处理后,接头抗拉强度为160MPa。分析结果表明,热处理后焊缝中的枝晶组织长大,部分柱状晶从界面层脱落进入焊缝,恶化了接头性能。界面层中的金属间化合物主要由CuZn5相组成,以柱状晶向焊缝生长。     

Domex700MC低合金高强钢药芯焊丝CO2气体保护焊焊接接头的组织与性能

用药芯焊丝CO2气体保护焊焊接Domex700MC低合金高强钢,用光学显微镜、硬度计和冲击试验机等对焊接接头的显微组织和力学性能进行了分析。结果表明：焊缝金属晶粒细小且分布均匀,有较多针状铁素体,但熔合区组织比较粗大,使熔合区附近塑性降低,为焊接接头的薄弱部位;焊缝金属显微硬度较高,为315HV,而在热影响区为225HV,出现软化现象;焊接接头力学性能优良,具有较高的抗拉强度（630．94MPa）和冲击功（135．34J）。     

LZ92镁锂合金激光焊接接头的显微组织与力学性能

采用CO₂激光焊接厚度为2mm的LZ92镁锂合金板,研究了焊接接头的显微组织、物相组成、显微硬度与拉伸性能。结果表明:LZ92镁锂合金焊接接头成形良好,焊缝中无明显气孔、裂纹等缺陷;母材与焊缝的物相组成相同,由α相、β相和中间相Mg₇Zn₃组成;母材由等轴状β相和枝晶状与颗粒状α相组成,热影响区由粗大的β相和少量细小颗粒状α相组成,焊缝中大量细针状和细小颗粒状α相均匀分布在β相中,β相晶界消失;焊缝的硬度最高,母材的次之,热影响区的最低;焊接接头的抗拉强度为158MPa,为母材的868.%,断后伸长率为27%;焊接接头的拉伸断口位于影响区与焊缝间的熔合线处,断口由韧窝和解理面组成,断裂形式为混合型断裂。     

Effects of weld cross-section profiles and microstructure on properties of pulsed Nd:YAG laser welding of Ti6Al4V sheet

In this study, the influence of weld cross-sectional profiles and microstructure, under different welding conditions, was investigated on the mechanical properties of pulsed Nd:YAG laser-welded joint of Ti6A14V alloy. The V- and H-shaped weld cross-section profiles were obtained under low and high heat input, respectively. The microstructure in the fusion zone (FZ) of V- and H-shaped welded joint consisted of a fine acicular martensitic α′ solidification structure within the prior-β grains, responsible for the maximum hardness in the FZ. Tensile tests revealed that the V-shaped welded joint fractured at the near heat-affected zone (HAZ)/base metal (BM) interface, but the H-shaped welded joint fractured in the BM. Furthermore, the tensile strength of the V-shaped welded joint was lower than that of the H-shaped welded joint. This was attributed to the fact that the heterogeneity of strain distribution at the interface of HAZ and BM of the V-shaped welded joint was greater than that of the H-shaped welded joint during tensile process.     

Effect of welding heat input on fatigue life of quenched boron steel and FB steel lap joint

The effect of welding heat input on the fatigue life of a quenched boron steel and ferrite-bainite (FB) steel lap joint was investigated. Boron steel was quenched and welded with FB steel in heat input ranging from 0.29 to 0.67 kJ/mm. Boron, which can increase hardenability, affected the microstructure and hardness of the weld metal and heat affected zone (HAZ). The hardness of the weld metal and HAZ increased with decreasing welding heat input, and the high hardness of the weld metal and boron steel HAZ prevented the initiation of cracks in the stress concentration area around the bead. The bead width increased with increasing heat input, and the results of finite element method (FEM) showed that the maximum stress in the notch of the weld joint decreased when the bead width was increased. That is to say, the fatigue life increased when the weld joint had wider bead width. Finally, while the fatigue life was affected by the residual stress, the variation of the welding heat input used in this study had hardly any affect on the residual stress distribution.     

Thermo-mechanical treatments of Sc- and Mg-modified Al–Cu alloy welds

High-strength heat-treatable aluminum alloy AA2219 finds application in aerospace industries. Though it has good weldability, with alternating current–tungsten inert gas welding, the joint efficiency obtained is only 40%, particularly in thicker plates. In the present study, an attempt has been made to improve the weld metal properties by modifying the chemistry of fusion zone and post-weld thermo-mechanical treatments. Fillers were made through casting route by melting conventional 2319 filler with Sc and Mg. Two levels of Sc (0.3% and 0.6%) and four levels of Mg (0.3% to 0.6%) were varied. Compressive deformation was done on the fusion zone of the weld to get three levels of percentage of reduction (4%, 8%, and 12%). As welded specimens and welds after compressive deformation, those were subjected to post-weld aging treatments at 190ºC for different periods up to 100 h. Compressive deformation on the welds made with modified filler of 2319 with Sc and Mg resulted in significant improvement in the weld metal strength.     

Determination of Elastoplastic Mechanical Properties of the Weld and Heat Affected Zone Metals in Tailor-Welded Blanks by Nanoindentation Test

The elastoplastic mechanical properties of the weld and heat affected zone metals have comparatively major impact on the forming process of tailor-welded blanks. A few scholars investigated the elastoplastic mechanical properties of the weld and heat affected zone, but they only simply assumed that it was a uniform distribution elastoplastic material different from the base materials. Four types of tailor-welded blanks which consist of ST12 and 304 stainless steel plates are selected as the research objects, the elastoplastic mechanical properties of the tailor-welded blanks weld and heat affected zone metals are obtained based on the nanoindentation tests, and the Erichsen cupping tests are conducted by combining numerical simulation with physical experiment. The nanoindentation tests results demonstrate that the elastoplastic mechanical properties of the weld and heat affected zone metals are not only different from the base materials, but also varying between the weld metals and the heat affected zone metals. Comparing the Erichsen cupping test resulted from numerical with that from experimental method, it is found that the numerical value of Erichsen cupping test which consider the elastoplastic mechanical properties of the weld and heat affected zone metals have a good agreement with the experimental result, and the relative error is only 4.8%. The proposed research provides good solutions for the inhomogeneous elastoplastic mechanical properties of the tailor-welded blanks weld and heat affected zone metals, and improves the control performance of tailor-welded blanks forming accuracy.     

14NiCrMo10 6V与Q345E钢过渡匹配焊接接头的组织与力学性能

采用E551T1-Ni2药芯焊丝对Q345E钢与14NiCrMo10 6V钢进行焊接,并通过室温拉伸、弯曲、冲击、硬度试验以及金相分析等对焊接接头的力学性能与显微组织进行了研究。结果表明:采用此焊丝可以获得拉伸、弯曲和冲击性能均良好的焊接接头,焊缝硬度在200～250HV之间;焊缝处晶界组织为先共析铁素体、少量无碳贝氏体(从晶界伸向晶内),晶内为针状铁素体与珠光体,个别部位有粒状贝氏体;Q345E钢侧热影响区与焊缝过渡区的组织为沿晶界析出的块状先共析铁素体和向晶内生长的条状铁素体以及少量的珠光体和贝氏体;14NiCrMo10 6V钢侧热影响区与焊缝过渡区的组织为板条状马氏体。