TC4/TA17异种钛合金激光焊接接头显微组织和力学性能

研究TC4/TA17异种钛合金激光焊接接头的显微组织和力学性能。结果表明,TC4/TA17异种钛合金激光焊接头焊缝的显微组织为片状α′马氏体,TC4侧靠近母材的热影响区和TA17侧靠近母材的热影响区只发生α相向β相转变,TC4侧靠近焊缝的显微组织为残余α相+针状α′马氏体,TA17侧靠近焊缝的显微组织为残余α相+片状α′马氏体。TC4/TA17异种钛合金激光焊接头的显微硬度呈不对称分布,焊缝的显微硬度最高,TA17母材显微硬度最低。TC4/TA17异种钛合金激光焊接接头断裂在TA17母材,断口呈现韧性断裂形貌。     

等离子弧焊Q345B和430不锈钢异种接头的微观组织与性能

摘要： 采用等离子弧焊对3 mm厚的Q345低合金钢与430不锈钢进行异种钢焊接,并对接头微观组织、力学性能及耐腐蚀性能进行了研究。结果表明,当转弧电流为100 A时,等离子弧焊Q345B/430异种钢接头的焊缝组织为均匀分布的马氏体及针状铁素体,焊接接头综合性能优良。随着电流的增大,焊缝组织转变为粗大板条马氏体及铁素体。两侧热影响区组织均发生一定程度的粗化,且Q345B侧热影响区出现魏氏组织。焊接接头于焊缝处显微硬度最大,不同转弧电流条件下异种钢显微硬度分布趋势大致相同。不同转弧电流下,焊接接头抗拉强度均与430不锈钢相近,且均断裂在靠近焊缝的430母材侧,转弧电流为100 A时接头抗拉强度最大值427 MPa。焊接接头的耐腐蚀性能与焊接电流呈负相关趋势。 创新点： 试验结果为铁素体低合金钢与铁素体不锈钢异种钢接头的应用提供了工艺数据与支撑。     

焊接电流对Ti2AlNb/TC18焊接界面性能及元素扩散的影响

采用真空电子束焊接对Ti2AlNb和TC18合金进行连接,研究了不同焊接电流时焊接界面的性能及元素扩散情况。结果表明:焊接接头在室温和高温下均获得了较高的抗拉强度。采用同一电流焊接时,TC18侧热影响区的显微硬度值高于该合金基体却低于该侧焊缝区,而Ti2AlNb合金侧热影响区的显微硬度值均高于该侧焊缝区和Ti2AlNb合金基体;在28 mA的焊接电流下,焊接界面的整体显微硬度值均较高,这是因为焊接界面形成了含量较多且尺寸较小的α′马氏体和O相,对界面起到了强化作用。在不同的焊接电流下,合金元素均在焊缝和两侧母材交界处存在较大的浓度梯度,其原因是焊缝金属的快速凝固使得各合金元素没有足够的时间和能量进行充分扩散。     

TC17钛合金线性摩擦焊接头组织及力学性能分析

针对固溶时效态TC17钛合金焊态及焊后热处理态线性摩擦焊接头,进行显微组织及力学性能对比分析. 结果表明,焊态时焊缝组织发生了回复与再结晶,由于焊后冷却速度较快,生成了亚稳定β相,焊缝区发生了软化;热力影响区组织沿受力变形方向拉长、细化、交替呈带状分布,加工硬化程度较高,显微硬度明显高于其它区域;热影响区由于二次次生α相基本溶解于亚稳定β相,导致显微硬度显著降低. 经过焊后热处理,亚稳定β相发生时效分解,析出了弥散程度更高的针状次生α相使得焊接区硬度大幅度提高. 由于亚稳定相的生成,焊态接头发生软化,拉伸均断裂在焊缝区,抗拉强度达到母材强度91.8%,断口呈脆性断裂形态;焊后热处理态接头由于二次次生α相的析出,起到弥散强化的作用,拉伸试验均断在母材,断口呈典型韧性断裂形态.     

Correlation Between Tensile Strength and Hardness of Electron Beam Welded TC4-DT Joints

Correlation between tensile strength and hardness for damage-tolerant Ti-6Al-4V (TC4-DT) alloy and its electron beam welded joints was investigated. Yield strength (YS), ultimate tensile strength (UTS) and strain hardening coefficient of base metal and weld metal were obtained using uniaxial tensile tests. Microhardness of the base metal, heat affected zone, and weld metal was measured. Then, the linear correlations among the yield strength, tensile strength, and hardness were proposed. Moreover, correlation between strain hardening coefficient and the ratio of YS to UTS (YS/UTS) was established. The results indicate that microhardness can be used to predict the YS and UTS of the TC4-DT welded joint successfully. In addition, the strain hardening coefficient can be predicted by the YS/UTS. The prediction of strength and strain hardening coefficient is in agreement with the experiments. The correlations are applicable and valuable for the strength prediction of narrow welded fusion zone and heat affected zone based on the microhardness measurement.     

激光快速成形TA15钛合金氩弧焊接头组织及力学性能

对激光快速成形TA15钛合金与轧制TA15钛合金薄板进行了氩弧焊接试验,观察分析了焊接接头各区域组织特征,测试了焊接接头各区域的显微硬度以及室温拉伸性能.结果表明,激光快速成形件与轧制薄板氩弧焊焊缝凝固组织是具有粗大片状α+β组织特征外延定向生长的柱状晶.轧制件对焊接热影响敏感性强,热影响区晶粒发生严重长大现象,激光成形件靠近焊缝热影响区晶粒转变为等轴晶,距焊缝较远的热影响区仍保持柱状晶.激光成形件热影响区硬度最高,焊缝区及轧制件热影响区的硬度最低.焊接接头抗拉强度低于母材,塑性与轧制件相当,断裂位置位于轧制件热影响区.     

热处理对TC17(α+β)/TC17(β)线性摩擦焊接头组织及力学性能的影响

针对热处理前后TC17(α+β)/TC17(β)钛合金线性摩擦焊接头组织和性能进行了对比分析. 结果表明,焊态时焊缝区组织发生动态回复和再结晶,两侧的热力影响区组织均被不同程度地拉长,热处理后焊缝中的亚稳相分解析出弥散的α和β相,TC17(α+β)侧热力影响区的初生α相有所长大. 焊态接头焊缝区显微硬度比母材低,接头的抗拉强度和屈服强度略低于母材,分别达到母材的91.9%,96.2%,接头拉伸性能试件断裂位置均在焊缝区;经过热处理,母材显微硬度未发生明显变化,焊缝区显微硬度显著提高,接头抗拉强度和屈服强度达到与母材相当,与焊态相比分别提高11.9%,8.2%,接头拉伸性能试件断于母材区.     

镍基高温合金焊接接头组织性能及工艺优化

采用不同的焊接工艺参数,对GH4169镍基高温合金薄板进行MIG焊接正交试验。通过金相试验,观察镍基高温合金焊接接头的显微组织,可以划分为焊缝中心等轴晶区、焊缝边缘柱状晶区、热影响区和母材组织。利用室温拉伸和显微硬度试验,测定镍基高温合金焊接接头的抗拉强度、断后伸长率与显微硬度等力学性能,并与母材的力学性能进行比较。使用极差分析法,研究焊接电流、电弧电压与焊接速度对接头力学性能的影响规律,并获得了优化的焊接工艺参数。     

Investigations of microstructures and properties in electron beam welded joints of TiAl to TC4

The normally centered electron beam and non-centered electron beam welding of TiAl to TC4 was investigated in order to analyze the electron beam weldability between TiAl/TC4 dissimilar materials. Macroscopic cold crack easily occurred near TiAl substrate in the joints. The optimal tensile strength was related to the welding heat input. The weld structures were composed of bulky columnar grains and equiaxed grains. The isolated phases consisted of large quantities of α2 -Ti3Al phase, small quantity of B2 phase, γ-TiAl phase and YAl2 phase. Insufficient melting of the base metal occurred in the weld when the beam position leaned to the TC4 side. The tensile strength could be improved when the deflection was limited in the optimum range. Otherwise, non-fusion zone was easily generated in the weld, which led to the low tensile strength.     

TC21+TC4-DT线性摩擦焊接头组织与力学性能试验

针对高强TC21和中强TC4-DT异种钛合金进行线性摩擦焊工艺研究,对接头进行不同热处理,接头微观组织和力学性能进行试验分析. 结果表明,TC21 + TC4-DT线性摩擦焊接头飞边成形良好,飞边表面光滑根部无明显缺陷存在;焊态条件下焊缝组织为典型的魏氏组织结构特征,热处理后焊缝组织析出弥散的针状α相,随着热处理温度的升高析出的针状α相逐渐长大粗化,致使接头冲击和断裂性能先上升后下降;接头拉伸性能与TC4-DT母材相当;700℃/3 h热处理接头、母材高周疲劳性能试验结果表明,接头的疲劳极限达到558 MPa,与TC4-DT基体相当,焊缝组织细化是提高接头疲劳极限的重要原因.     

钛钢复合板搅拌摩擦焊接接头组织与力学性能

采用搅拌摩擦焊对接工艺焊接厚度为2 mm的TA2-Q235B钛钢复合板。采用光学显微镜和扫描电子显微镜观察焊接接头显微组织及断口形貌,并采用拉伸试验机和显微硬度计测试焊接接头力学性能及不同区域的显微硬度。结果表明,钛钢复合板焊接接头从上到下分为上部钢焊接区,中部钛钢混合区及下部钛焊接区3个区域,其中钛钢混合区呈交替层叠状结构。当轴肩旋转速度为300 r/min,焊接速度为40 mm/min时,焊接接头的抗拉强度为386 MPa,达到母材强度的80%以上,焊接区域的硬度平均值为243.5 HV,焊接接头断裂源于结合较弱的前进侧热机影响区域。     

薄板TC4钛合金脉冲电子束焊接技术研究

脉冲电子束焊接是指将电子束流调制成脉冲方波的形式进行焊接的一种先进技术。脉冲束流能提高被焊金属蒸发率,从而提高焊接效率、增加焊缝深宽比。本文采用常规直流电子束和不同频率脉冲电子束对1.2 mm薄板TC4钛合金进行了焊接工艺试验,并对接头进行了微观组织与力学性能检测。结果表明：脉冲电子束焊接能够形成无熔合缺陷的焊缝,随着频率的增加,焊缝咬边和背面余高减小,表面成形得到改善;由于焊接热循环变化,脉冲束流可加快熔池冷却速度,细化组织晶粒;直流和脉冲电子束焊接接头拉伸时均断裂在母材区,拉伸强度不低于母材;高频脉冲电子束可提升焊接接头塑性和焊缝区、热影响区的显微硬度,频率为10 kHz时,焊接接头的断后伸长率可达14.9%,约为母材的80%,焊缝区和热影响区的显微硬度分别为375 HV和368 HV。     

Improving formability of laser welded automotive dual phase steels with local cooling

Abstract

A new laser welding process with the local cooling was presented and applied to two automotive dual phase steels, DP780 and DP980. The microstructure, microhardness, tensile properties of welded joints and limiting dome height (LDH) of welded blanks were investigated. It is observed that the local cooling during laser welding process can greatly reduce the martensite tempering and thus reduce the heat affected zone softening. The laser welded joints with the local cooling all failed at the base metal, and exhibit the comparable strength and ductility with the base metal. For the welded blanks with the local cooling, LDH is increased significantly, and failure initiates from the weld and propagates perpendicular to the weld.     

Microstructures and microhardness for sheets and TIG welded joints of TA15 alloy using friction stir spot processing

Effects of friction stir spot processing (FSSP) on the microstructures and microhardness of tungsten inert gas (TIG) welded TA15 titanium alloy joints were investigated. The macro/micro structural observation and microhardness evaluation of the TA15 alloy sheets and TA15 TIG welded joints were carried out using optical microscope and microhardness tests. The results show that FSSP effectively improves the microstructure and increases the microhardness of the TA15 sheets. As for the TIG welded joints, FSSP also effectively improves the microstructure of joints. And the average microhardness value in weld nugget zone is improved significantly, while a small increase of this value in heat affected zone is observed. The hardness in stirring zone is significantly higher than that in the base metal. Two peak values of hardness appear along the width direction in stirring zone. After FSSP, the average hardness of the weld zone of TA15 TIG welded joint is significantly higher than that before FSSP. Under the present process parameters, both the surface oxidation in TA15 sheets and in TIG welded joints after FSSP are not evident, while the surface forms the bright white layer, which is composed of a great multitude of fine grains.     

激光冲击处理对TC4氩弧焊焊缝力学性能的影响

采用激光冲击处理(LSP)工艺对TC4钛合金钨极氩弧焊焊缝进行焊后处理,分别检测经过激光处理的焊缝及未经处理的焊缝的表面显微硬度、接头的拉伸性能、接头的疲劳寿命。结果表明:与未经LSP处理的接头相比,TC4钛合金TIG焊焊缝经过激光冲击强化处理后,焊缝区域表面显微硬度降低,而焊缝热影响区表面显微硬度增大;焊接接头的抗拉强度、屈服强度、断后延伸率、疲劳寿命均得到了不同程度的提高。     

新型Al-Mg-Mn-Er合金TIG焊接头的微观组织及力学性能

对一种Al-Mg-Mn-Er合金薄板进行TIG填丝焊接,并研究接头的微观组织以及力学性能. 结果表明,焊缝中心为等轴树枝晶,熔合线附近未出现典型的联生结晶形貌,而是存在着一个宽度约为100 μm的细晶带,热影响区出现再结晶组织. 焊缝中的析出相主要以初生Al₃Er的形式存在,与母材相比,焊缝中初生Al₃Er的尺寸更加细小,分布更加均匀,焊缝中次生Al₃Er的数量相对较少,而且这些次生Al₃Er是焊接时母材中未熔化而保留下来的. 焊接区和热影响区的硬度均低于母材,其中焊缝区的硬度最低. 随着焊接热输入的增加,接头的抗拉强度先增加后减小,当焊接热输入为218 J/mm时,接头的抗拉强度最高,达到母材的71.4%,试样的断裂位置均位于焊缝区,断口形貌呈现韧性断裂特征.     

焊后热处理对输送H_2S介质压力管道维修焊接接头组织性能的影响

采用手工钨极氩弧焊(TIG焊)打底,焊条电弧焊(SMAW)填充、盖面的焊接工艺对输送H_2S介质压力管道(20钢)进行维修焊接,并对其焊接接头进行720～750℃下保温1h的焊后热处理.对热处理前、后焊接接头组织和性能进行分析研究,结果表明:720～750℃×1h热处理使焊缝区与热影响区成针状分布的魏氏组织铁索体晶粒得到细化,并使其呈退化形态;焊缝区、热影响区与母材的显微硬度整体呈下降趋势;焊接接头抗拉强度大幅度提高,断裂均处在远离焊缝的母材上.焊后热处理有效地降低了焊接接头的残余应力,改变了残余应力的分布特征,使其分布趋于"均匀",拉应力大幅度降低.     

Incoloy 825镍基高温合金电子束焊工艺及接头组织与力学性能分析

采用电子束焊,对空冷器管箱Incoloy 825镍基高温合金进行对接焊试验. 通过对焊接接头的组织观察,并结合拉伸力学性能以及接头的冲击韧性等试验,分析镍基高温合金电子束焊接头的组织和力学性能. 结果表明, 采用电子束焊焊接镍基高温合金可以得到良好的焊接接头,焊缝区组织由大片等轴晶和少量柱状晶组成;焊缝区没有出现明显的元素烧损现象;焊缝、热影响区硬度达到母材硬度值;焊缝接头抗拉强度达到600 MPa,接近母材抗拉强度,接头断裂形式为韧性断裂;焊缝和热影响区的冲击吸收能量高于母材区,其中焊缝区的冲击吸收能量达到了262 J,冲击断口形貌为韧窝状.     

焊后热处理对异种合金摩擦焊件组织与性能的影响

用金相观察、SEM分析和拉伸试验等方法研究不同的焊后热处理制度对异种合金(Ti2AlNb/TC11)线性摩擦焊接件显微组织与力学性能的影响。结果表明:仅进行时效热处理时,随着保温时间的延长或热处理温度的提高,焊缝两侧热影响区条状α/O相析出量不断增加,焊接接头强度也相应得到提高;固溶及时效热处理后,TC11合金侧热影响区在晶界上析出大量粗条状α相,Ti2AlNb合金侧热影响区晶界主要由条状O相构成,焊接接头强度超出母材TC11合金的强度。     

TC4厚壁管全位置PAW工艺及接头性能分析

介绍了一种适合TC4钛合金厚壁管的等离子弧焊接新工艺,通过对工艺参数分区控制和优化匹配,实现了钛合金管道全位置优质焊接.采用光学显微镜、扫描电镜以及显微维氏硬度仪分别对特征位置焊接接头的显微组织、断口形貌以及显微硬度进行表征.结果表明,特征位置接头焊缝区及热影响区显微组织均主要由网篮状α'相、针状α相以及粗大β相组成;接头拉伸性能良好,拉伸试样均断裂于母材处;冲击试样的断裂形式为韧性断裂;焊缝区及热影响区硬化区的硬度值高于母材.