5A06铝合金电子束焊接中镁元素的烧损行为

研究了5A06铝合金电子束焊接后熔池内镁元素的分布及其对焊缝硬度的影响,并分析了焊接参数对镁元素烧损行为的影响。结果表明：在同一熔池中随着深度的增加,镁元素含量增加,即烧损程度减小,同时显微硬度增大;随着加速电压和束流的增加,熔池熔深增加,镁元素烧损程度降低;随着焊接速度增加,镁元素烧损程度降低,熔深却减小。为减小镁元素烧损,在电子束焊接时可适当增加焊接的加速电压与束流,加快焊接速度。     

DP590镀锌双相钢CMT焊接接头气孔及锌层研究

镀锌钢因其优异的耐腐蚀性，常用于车身制造中，因此其焊接性受到广泛研究，而CMT焊接镀锌钢板时飞溅少，可以减少出现气孔的可能性，故CMT在镀锌钢板焊接应用中具有极大的优势。采用1.0mm厚的DP590热镀锌双相钢作为焊接母材，选用直径1.0 mm的BHG-2M焊丝作为焊接材料，利用CMT数字化焊机进行搭接焊。控制送丝速度与焊接速度作为焊接工艺参数，研究不同焊接工艺参数下焊接接头气孔和锌层烧损情况。通过能谱仪对锌层成分进行分析，并测量焊接接头正反面锌层烧损宽度。结果表明，焊缝中气孔的产生和焊接线能量密切相关，线能量越大，气孔率越低。焊缝上表面中心烧损严重，Zn元素基本完全蒸发，两侧烧损程度逐渐递减，越靠近焊缝中心的下表面锌层氧化程度越大。增加焊接速度或减小送丝速度，焊缝锌层烧损程度降低。     

快速凝固Mg-Zn-Y合金薄带组织和性能研究

在成功制备不同成分Mg—Zn—Y合金急冷快速凝固薄带基础上，利用XRF和XRD分析其成分和组织特点及其组织变化规律，采用腐蚀失重法、盐雾实验法、显微硬度测量等方法，系统研究了不同成分Mg—Zn—Y合金急冷快速凝固薄带的耐蚀性能和硬度变化规律。结果表明，随冷却速度的增大，Mg—Zn—Y合金凝固组织具有非晶化的趋势；MgZnY母合金块及其薄带在1％HCl、10％NaOH和5％NaCl溶液中腐蚀性能表现出相似的规律；在成分和冷却速率相同的条件下，Mg—Zn—Y合金的耐蚀性在10％NaOH溶液中最好，5％NaCl溶液中次之，而在1％HCl溶液中最差；在成分相同的条件下，随着冷却速度的增大，Mg—Zn—Y合金的显微硬度增大，而且薄带的显微硬度比同成分母合金块的高50％以上。最后，本文还对上述研究结果进行了初步分析。     

Al5TiB对Mg-8Zn-4Al-0.3Mn合金显微组织的影响

研究了Al5TiB对Mg-8Zn-4Al-0．3Mn铸造镁合金显微组织的影响。结果表明，Mg-8Zn-4Al-0．3Mn铸造镁合金的显微组织主要由Mg相、φ(Al2Mg5Zn2)相、τ(Mg32(Al，Zn)49)相组成。加入0．5％的Al5TiB可显著细化合金的铸态组织，晶粒大小由120～130μm减少到30～40μm。随着Al5TiB加入量的增加，合金的共晶α(Mg)相数量和合金的显微硬度均呈增加趋势。     

Zn对医用Mg-Mn合金显微组织的影响

Mg合金具有可降解性、生物学特性和力学相容性等一系列特性,是一种极具发展潜力的新型可降解生物医用材料。本文采用真空气氛保护金属型Mg-Zn-Mn合金,通过金相组织观察和硬度试验,研究了合金的性能。结果表明:纯Mg中添加合金元素Zn和Mn可显著地细化晶粒,Zn含量的变化对Mg合金晶粒尺寸影响较小;Mg合金硬度随着Zn含量的增加而提高,并且Zn具有较好的固溶强化效果;Mg合金固溶处理后,晶粒发生一定程度上的长大,Mg合金硬度随Zn含量的增加而提高,这说明固溶强化的效果强于晶粒粗化而造成的力学性能降低。     

Q235D多层激光熔覆实验研究

在Q235D钢表面进行多层激光熔覆Fe基合金粉末,实验结果显示基体与熔覆层之间以及熔覆层与熔覆层之间的冶金结合性较好,没有出现裂纹,并且基本无气孔,熔覆层的显微组织、表面硬度和显微硬度均显著优于基体。实验发现,多层熔覆时在不连续加工情况下,随着制备熔覆层数目的增多,在加工新的熔覆层时,之前已经制备完成的各熔覆层的硬度均会有不同程度的降低,并且距离基体越近的熔覆层其硬度降低越多,第一熔覆层显微硬度最低,往上层方向显微硬度逐渐增加,最后一层硬度最高,并且制备的层数越多这种硬度降低程度也会越显著。     

工艺参数对Cr12MoV表面激光熔覆M2高速钢高硬度涂层的影响

为增强轧辊表面硬度以提升轧辊工作寿命，采用1 kW光纤激光器在Cr12MoV表面制备M2高速钢熔覆层，探索最优激光工艺参数。通过着色探伤剂、X射线衍射仪及显微硬度仪，对不同激光功率和扫描速度下的熔覆层显微组织、成分、物相、硬度进行检测分析。结果表明：激光功率对熔覆层表面成形质量影响较大，扫描速度对其影响不明显；随激光功率增加，熔覆层表面平整度增强，裂纹数量降低，熔覆层组织成分分布越均匀，晶界偏析现象减弱，枝晶组织逐渐粗大，熔覆层显微硬度降低；熔覆层主要由Martensite、Austensite、Fe-Cr、MC、M2C相组成，熔覆层内的组织主要是树枝晶和胞状晶，MC、M2C等硬质相弥散分布在组织内；激光功率为1 000 W，扫描速度为180 mm/min时，熔覆层表面无裂纹，最大显微硬度为1 092HV0.2，是基体的2.63倍，满足工业性能需求。     

超声辅助激光熔覆TiCN镍基涂层组织及性能研究

为了探究超声频率对激光熔覆涂层的影响，设置5组对照实验。通过施加超声频率0 kHz、26 kHz、30 kHz、34 kHz和38 kHz辅助制备出TiCN增强镍基涂层，对各涂层宏观形貌、显微组织及耐磨性进行了研究。结果显示：施加超声不会使涂层产生新的物相且在一定程度上促进TiCN增强相的生成；增加超声频率，涂层中气泡数量减少，晶粒更细小紧密，涂层中团聚现象减少；增加超声频率，涂层显微硬度增加，当超声频率为38 kHz时涂层显微硬度最高且变化平稳；对比未施加超声的涂层，施加超声频率38 kHz时的涂层磨损量减少约30%，且主要磨损由粘着磨损转变为轻微犁削。     

LF6铝镁合金电子束焊接

研究了焊缝中合全元素Mg的烧损现象、焊接接头的力学性能和焊接热裂纹等问题。结果表明，电子束焊接LF6铝镁合金，其焊缝组织为微细等轴晶，熔合线附近为胞状树枝晶；Mg合金元素在焊缝上部和中心区有较大的蒸发损失；焊接接头存在一定的软化，其抗拉强度为母材的91．2%，除延伸率比母材高外，断面收缩率和冲击韧性值与母材相比均有所降低；在合适的参数匹配下，焊缝中不会出现热裂纹以及氧化膜所导致的熔合不良与夹渣等问题。     

Q460c钢激光相变硬化处理的组织和硬度

本文对Q460c钢板进行了激光淬火处理,研究了不同工艺参数对处理层的组织、形态及硬度等的影响。结果表明,激光相变硬化处理可明显细化Q460c钢的表层组织,且提高其表面硬度。随着激光功率的增加,淬硬层深逐渐变大,但当功率过大(P=1200W)时,发生微熔现象,表层晶粒粗大且合金元素烧损,硬度明显降低。当功率过低(P=700W和900W)时,表面相当于高温回火处理,硬度略有降低。     

薄板Al合金的TIG焊接头性能研究

针对薄板铝合金焊接时存在易烧穿、气孔、热裂纹和焊接变形等特点,分析了薄板Al合金TIG焊方法中常见的问题,采用各种有效措施加以解决。通过改变焊接电流和速度得到了一系列的焊缝。对各焊接工艺下的焊接接头进行了显微组织分析和力学性能测试,得出了不同焊接工艺参数下焊接接头的力学性能。讨论了焊接电流对接头力学性能的影响,同时分析了不同焊接工艺参数时焊缝尺寸的变化规律。     

Study on the burning loss of magnesium in fiber laser welding of an Al-Mg alloy by optical emission spectroscopy

In order to study the burning loss of magnesium, a specially designed device was used to capture the spectrum emitted from the keyhole plasma in deep penetration laser welding of aluminum alloy 5052. The content of magnesium in the weld bead was measured by an electron probe micro-analyzer (EPMA). The effect of the welding parameters on the spectral intensity of magnesium plasma was examined, and the distributions of the spectral intensity of magnesium plasma in the radial and depth directions of the keyhole were investigated. Finally, the mechanism of the magnesium loss was analyzed. The results indicate that burning loss of magnesium can be monitored by spectral analysis technique. The welding parameters have a great effect on the burning loss of magnesium. The influence of welding speed on the burning loss of magnesium on the top surface is dependent on the penetration regime. The distribution of magnesium in the weld is not uniform. In the radial direction of the weld bead, the content of magnesium increases from the center to the edge of the keyhole. In the depth direction of the weld bead, the content of magnesium decreases firstly and then increases from the top to bottom. The maximum burning loss of magnesium occurs at the middle of the weld bead.     

6061/A356异种铝合金脉冲MIG搭接焊*

利用直流脉冲MIG焊接技术,进行6061变形铝合金与A356铸造铝合金板材的搭接焊接,并分析接头的力学性能、微观组织及元素分布。拉伸试验结果表明,当A356铸造铝合金板在上,6061变形铝合金板在下,焊枪行走速度为10 mm/s时,搭接接头抗拉强度最高,为95 MPa。接头拉伸试样的断裂位置都位于焊缝区,断裂形式主要为混合型断裂。微观组织及元素分析结果表明,在A356铝合金一侧的部分熔融区内发生Fe和Mg元素偏聚,形成了片状Al-Fe-Si相和颗粒状Al-Fe-Mg-Si相,这两种富Fe相会削弱接头性能。在6061铝合金一侧的部分熔融区内产生了晶界液化,形成了Al-Mg-Si-Cu相+Al固溶体贫化区的液化组织,且该相周围有Fe元素偏聚。三角区是接头中最薄弱的位置,接头拉伸试样均起裂于此并最终断裂于焊缝。     

Laser welding of Haynes 188 alloy sheet: thermal stress analysis

Laser welding of Haynes 188 alloy sheets is carried out. Temperature and stress fields developed in the welding section are predicted numerically incorporating the finite element algorithm. The microstructural changes in the welding region are examined using the optical and electron scanning microscopes. The microhardness variation across the weld zone is measured and associated with the residual stress formed in this region. It is found that the microhardness follows the residual stress distribution in the weld core. The maximum residual stress is less than the elastic limit of the substrate material.     

Effect of welding processes on tensile properties of AA6061 aluminium alloy joints

The present investigation is aimed at to study the effect of welding processes such as GTAW, GMAW and FSW on mechanical properties of AA6061 aluminium alloy. The preferred welding processes of these alloys are frequently gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) due to their comparatively easier applicability and better economy. In this alloy, the weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often causes inferior weld mechanical properties and poor resistance to hot cracking. Friction stir welding (FSW) is a solid phase welding technique developed primarily for welding metals and alloys that heretofore had been difficult to weld using more traditional fusion techniques. Rolled plates of 6 mm thickness have been used as the base material for preparing single pass butt welded joints. The filler metal used for joining the plates is AA4043 (Al-5Si (wt%)) grade aluminium alloy. In the present work, tensile properties, micro hardness, microstructure and fracture surface morphology of the GMAW, GTAW and FSW joints have been evaluated, and the results are compared. From this investigation, it is found that FSW joints of AA6061 aluminium alloy showed superior mechanical properties compared with GTAW and GMAW joints, and this is mainly due to the formation of very fine, equiaxed microstructure in the weld zone.     

评定铝合金焊接接头力学性能的新途径

采用常规试验方法来测定铝合金型材构件焊接接头各区的力学性能及其变化规律是很困难的。而接头性能直接影响着结构焊接工艺的选择和强度计算。通过测定铝合金微型剪切试验和拉伸试验的性能参数，研究得出了这些性能参数之间的数学关系式。可利用这些关系式评定铝合金焊接接头的力学性能。微型剪切试验为铝合金焊接接头力学性能的评定提供了一个新途径。     

2A14厚板铝合金SSFSW角焊缝接头组织及性能

采用自主研制搅拌针长度为8.5mm的静止轴肩搅拌工具和2A14-T4厚板铝合金进行150°角焊缝接头静止轴肩搅拌摩擦焊工艺试验,探讨焊接工艺参数对接头组织和力学性能的影响规律。结果表明:在500~700r/min主轴转速与40~100mm/min焊接速度范围内均可获得表面光滑无内部缺陷的角焊缝接头,其外观尺寸可精确控制基本无残余焊接角变形。焊缝区主要由焊核(Stir zone,SZ)组成,SZ形状类似搅拌针圆锥台状或椭圆状、其宽度沿厚度方向分布比较均匀;热力影响区(Thermal mechanical affected zone,TMAZ)及热影响区(Heat affected zone,HAZ)宽度明显较小。焊缝区硬度分布具有明显不均匀特征,最薄弱区位于TMAZ与HAZ的交界处。主轴转速变化对焊缝区平均硬度影响较小,但随着焊接速度增加其平均硬度明显增大。角焊缝前进侧等效拉伸强度大于后退侧,等效拉伸强度随转速增加而减小,焊速的增大而增大。在500r/min-100mm/min焊接工艺下所得到的接头等效拉伸强度最高,可达到母材的79.24%。在拉-剪复合承载模式下,角焊缝拉伸试样宏观塑性变形很小呈现脆性断裂特征。     

铝合金双面双弧同步立焊工艺特征与接头组织性能分析

采用双面双弧同步立焊工艺方法,对8 mm厚5083铝合金进行自熔试验,I形坡口一次熔透,焊缝成形美观。通过调节两侧电弧热量配比研究熔池成形规律,并从焊接接头的微观组织、力学性能分析其连接机理。研究结果表明,随着热输入的增加,双面双弧同步立焊热量加速集聚,熔深以三次幂函数的速度增大。双面双弧同步立焊接头轮廓呈“双曲线形”,而相同热输入下的单面焊接头则呈“倒马鞍形”。总热输入一定的情况下,双面双弧接头正面熔宽随能量配比系数的增大而增大,反面熔宽随能量配比系数的增大而减小,中间熔宽基本不变,熔化面积随能量配比系数的增大先增大后减小;能量配比系数一定时,随着焊速的增大,接头熔宽和熔化面积均减小。母材组织为条带状纤维织构,热影响区发生静态回复与再结晶,变形组织消失,产生新晶粒,焊缝区主要由α-Al固溶体、β相(Al8Mg5)质点和骨骼状的Mg2Si析出相组成。焊缝的抗拉强度随着能量配比系数的增大而减小,拉伸断裂形式为韧性断裂。热影响区出现软化现象,双弧交汇区硬度低于正面焊缝区。     

Predictions of the optimized friction stir welding process parameters for joining AA7075-T6 aluminum alloy using preheating system

The scope of this investigation is to evaluate the effect of welding parameters on the mechanical properties and microstructural features of 3-mm-thick AA7075-T6 aluminum alloy subjected to gas heating system as a preheating source during friction stir welding. Toward this end, a gas heating system was designed to heat up the weld seam just ahead of rotating tool to soften the material before being stirred. Three welding parameters, five levels, and a central composite design (CCD) have been used to minimize the number of experimental conditions. The joining parameters such as tool rotational speed, welding speed, and shoulder diameter have a significant influence on determining the mechanical properties of the welded joints. It was found that using preheating system mostly can result in higher total heat input into the weld joint and effectively reduces the formation of defects when unsuitable process parameters were used. Also, an attempt has been made to establish the mathematical model to predict the tensile strength and microhardness of the joints. The optimal welding conditions to maximize the final responses were investigated and reported. The results show that the joint fabricated at a rotational speed of 1,050 rpm, welding speed of 100 mm/min, and shoulder diameter of 14 mm exhibited higher mechanical properties compared to other joints.     

Fibre laser welding of dissimilar alloys of Ti-6Al-4V and Inconel 718 for aerospace applications

Challenges in dissimilar materials welding are the differences of physical and chemical properties between welding materials and the formation of intermetallic brittle phases resulting in the degradation of mechanical properties of welds. However, dissimilar materials welding is increasingly demanded from the industry as it can effectively reduce material costs and improve the design. In aerospace applications, Ti-6Al-4V titanium alloy and Inconel 718 nickel alloy have been widely used because of their superior corrosion resistance and mechanical properties. In this study, a single-mode continuous-wave fibre laser was used in butt welding of Ti-6Al-4V to Inconel 718. Investigations including metallurgical and mechanical examinations were carried out by means of varying processing parameters, such as laser power, welding speed and the laser beam offset position from the interface of the metals. Simple analytical modelling analysis was undertaken to explain the phenomena that occurred in this process. Results showed that the formation of intermetallic brittle phases and welding defects could be effectively restricted at welding conditions produced by the combination of higher laser power, higher welding speed and shifting the laser beam from the interface to the Inconel 718 alloy side. The amount of heat input and position of laser beam to improve the Ti-6Al-4V/Inconel 718 weld quality are suggested.