铝合金厚板静止轴肩搅拌摩擦焊接头组织及性能

采用8.5 mm厚度2A14-T4铝合金和自主研制搅拌工具进行静止轴肩搅拌摩擦焊（stationary shoulder friction stir welding,SSFSW）实验,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：只有在低转速工艺参数范围内（转速ω=400~600 r/min与焊接速率v=60~120 mm/min）可获得焊缝表面光滑、无缺陷厚板铝合金SSFSW焊接接头。SSFSW焊缝区主要由焊核区（NZ）组成,周围热力影响区（TMAZ）及热影响区（HAZ）宽度明显减小,焊核区与搅拌针形状类似且由两种不同尺寸细小等轴晶构成,前进侧NZ晶粒比后退侧NZ更为细小。接头显微硬度呈"W"状分布,NZ硬度值可达到母材硬度80%~90%,TMAZ与HAZ交界处存在软化区,硬度最低为母材硬度72%左右。在给定ω=500 r/min,v=140 mm/min焊接参数下,SSFSW接头抗拉强度可达到母材的88%,断裂位置多位于后退侧TMAZ与HAZ交界处软化区,具有韧性断裂特征。     

汽车轮辋用钢搅拌摩擦焊接头组织及力学性能

目的 为搅拌摩擦焊在轮辋钢的应用提供理论数据。方法 选用厚度为4.5 mm的江铃汽车V362轮辋钢板B380CL,采用不同的焊接参数,获得搅拌摩擦焊接头,对焊缝宏观成形及微观组织进行分析,研究焊接参数对组织的影响;通过进行拉伸试验和硬度测试,分析焊接参数对焊接接头性能的影响;对接头焊缝进行X-Ray无损探伤。结果 当搅拌头旋转速度为950 r/min,焊接速度分别为37.5, 47.5, 60 mm/min时,均能形成焊接接头。焊接速度为47.5 mm/min时,焊缝宏观成形较好,微观组织无缺陷,微观组织为铁素体和珠光体,抗拉强度最高,超过母材;焊接接头各区域微观组织硬度较母材高,伸长率较焊接速度为37.5 mm/min时的接头高。结论 搅拌摩擦焊实现轮辋钢的对接,该研究中旋转速度950 r/min,焊接速度47.5 mm/min为最佳工艺参数,接头抗拉强度超过母材。     

1.4003铁素体不锈钢与Q235-C钢焊接接头的组织和力学性能

采用室温拉伸、不同温度冲击、硬度及金相检验等分析方法对用熔化极混合气体保护焊焊接的1.4003铁素体不锈钢与Q235-C钢焊接接头的显微组织和性能进行了研究.试验结果表明:该焊接接头的抗拉强度与母材相当,焊缝的冲击性能略低于母材,1.4003铁素体不锈钢的热影响区(HAZ)冲击性能较差,焊缝为奥氏体+铁素体双相组织;Q235-C钢的熔合区出现明显界限,1.4003铁素体不锈钢焊接热影响区为晶粒粗大的单一铁素体组织.     

厚板7022铝合金搅拌摩擦焊接实验研究

对10mm厚度的7022铝合金进行了搅拌摩擦焊接,获得表面光滑的焊接接头,并通过X射线检测焊缝无裂纹和气孔。研究该搅拌摩擦焊接头不同区域的显微组织特征,并通过拉伸、冲击和硬度试验分析了焊接接头的力学性能。结果表明,焊缝处组织为细小均匀的等轴晶粒;在搅拌头转速为400r/min,焊接速度为100mm/min时焊接接头的抗拉强度、屈服强度均比母材高;焊接接头的冲击韧性比母材高;焊接接头显微硬度比母材稍低,焊接接头具有良好的力学性能。     

旋转速度对高强度钢Q&P980搅拌摩擦焊接头组织与性能的影响

为了促进高强度钢在汽车领域的应用,解决高强度钢在采用常规熔化焊进行焊接时出现的问题,利用搅拌摩擦焊接技术对1. 2 mm厚的高强度钢QP980进行焊接试验,并利用激光共聚焦显微镜、扫描电子显微镜、万能试验机和显微硬度计等手段研究旋转速度对高强度钢QP980搅拌摩擦焊接头的微观组织和力学性能的影响。研究发现,在不同旋转速度下均获得了没有缺陷的焊缝,接头组织呈典型的"碗状"组织形貌。旋转速度为200 r/min时,接头搅拌区组织仍为马氏体与铁素体组织,但晶粒尺寸相比母材明显细化且马氏体含量相比母材增多。随着旋转速度的提高,马氏体含量会继续增多,旋转速度为400 r/min时搅拌区组织基本全部为马氏体组织,旋转速度为600 r/min时搅拌区组织为马氏体和贝氏体的混合组织。接头显微硬度结果显示,搅拌区的硬度明显高于母材,搅拌区与母材之间存在一个软化区。旋转速度为400 r/min时,接头抗拉强度最高,达到1 070MPa,为母材的99%,基本等同于母材的抗拉强度;接头的断后伸长率为11. 2%,达到母材的50%。旋转速度为200 r/min时,接头断裂于搅拌区,其他旋转速度下接头均断裂于软化区,断裂于软化区的断口形貌呈现韧性断裂特征。     

超窄间隙激光焊接TC4钛合金接头组织及性能研究

以TA2为焊丝,采用超窄间隙激光焊接方法焊接了10 mm的TC4钛合金板,间隙为2 mm。利用光学显微镜(OM)、扫描电镜(SEM)和拉伸试验机分析了TC4钛合金接头的组织与性能。结果表明,选取合适的工艺可以实现TC4钛合金超窄间隙激光填丝焊接,获得无缺陷的焊接接头。接头由母材、热影响区、熔合区、焊缝组成,界线清晰。其中热影响区为网篮状组织,焊缝由大β晶粒组成,大晶粒内部为杂乱的α+α′相针状组织,热影响区晶粒明显细化。由于超窄间隙的啮合效应,接头最大抗拉强度为893 MPa,达到母材的84.7%,断裂位置在焊缝中心。焊缝区和热影响区的显微硬度高于母材,且在热影响区的显微硬度最大,接头整体显微硬度呈马鞍状分布。     

5083铝合金搅拌摩擦焊接头的显微组织与力学性能

对8 mm厚5083-H321铝合金板进行了搅拌摩擦焊接试验,研究了焊接工艺参数对搅拌摩擦焊接头显微组织和力学性能的影响。结果表明:该搅拌摩擦焊接头焊核区显微组织为细小的等轴晶组织,热机影响区为拉伸弯曲变形组织,热影响区非常窄,其晶粒尺寸与母材相当;综合接头表面形貌和拉伸性能得到较佳的搅拌摩擦焊接工艺参数为使用搅拌针为三棱形带螺纹、轴肩为内扣型的搅拌头,主轴转速为300 r·min^-1,焊接速率为120 mm·min^-1;在该工艺条件下接头表面成形良好,抗拉强度可达到母材的94.5%。     

Ti60/TC17电子束焊接接头的组织及显微硬度

对Ti60/TC17异种材料进行电子束焊接,研究接头成型特点、焊缝组织、热影响区组织及显微硬度。结果表明:Ti60/TC17电子束焊接接头的焊缝组织为对称生长的枝晶状组织;Ti60侧热影响区与焊缝有明显分界,组织为针状α相;TC17侧热影响区为细小的粒状α相。焊缝的显微硬度低于母材的显微硬度。     

热输入对Q1100钢焊接接头低温韧性及耐蚀性能的影响

采用10 kJ/cm和15 kJ/cm两种焊接热输入对Q1100超高强钢进行熔化极气体保护焊,研究焊接接头的组织性能及局部腐蚀行为。结果表明：两种热输入焊接接头的焊缝组织主要为针状铁素体和少量的粒状贝氏体,粗晶区组织均为板条贝氏体,细晶区组织均为板条贝氏体和粒状贝氏体,临界相变区组织为多边形铁素体、马奥岛和碳化物的混合组织。两种热输入焊接接头中电荷转移电阻均为母材>热影响区>焊缝区,母材耐蚀性最好,热影响区次之,焊缝区耐蚀性最差。在腐蚀过程中,焊缝区作为阳极最先被腐蚀,当腐蚀一定时间后,腐蚀位置发生改变,阳极腐蚀区域转移到母材区,而焊缝区作为阴极得到保护。热输入为10 kJ/cm时,焊接接头具有更好的低温韧性和耐蚀性,其焊缝和热影响区-40℃冲击功分别为46.5 J和30.2 J。     

异种铝合金回填式搅拌摩擦点焊工艺的研究

目的 研究搅拌头转速和轴套下压量对异质铝合金回填式搅拌摩擦点焊接头的组织及力学性能的影响。方法 采用回填式搅拌摩擦点焊技术对7050铝合金和2524铝合金进行搭接焊试验,焊接完成后利用光镜、体式显微镜、扫描电镜对组织进行观察,另外,测试拉伸剪切载荷和显微硬度分布,最后对断裂行为进行了研究。结果 接头区域可以分为焊核区、热力影响区、热影响区、母材4个区域,焊核区晶粒呈细小等轴状,热力影响区晶粒呈粗大长条状。随搅拌头转速的增大,拉剪载荷降低,当转速为1500 r/min时拉剪载荷值最高,其值为7.499 44 kN。热影响区的显微硬度比母材低,最小值为HV106。接头的断裂方式可以分为剪切型断裂、塞型断裂、剪切-半环型断裂。结论 在一定工艺参数范围内,通过适当降低搅拌头转速能显著提高接头的拉剪载荷,轴套下压量对接头的断裂方式影响显著。     

Microstructures and mechanical properties of friction stir welds on 9% Cr reduced activation ferritic/martensitic steel

In this study,the microstructures and mechanical properties of 9%Cr reduced activation ferritic/martensitic(RAFM) steel friction stir welded joints were investigated.When a W-Re tool is used,the recommended welding parameters are 300 rpm rotational speed,60 mm/min welding speed and10 kn axial force.In stir zone(SZ),austenite dynamic recrystallization induced by plastic deformation and the high cooling rates lead to an obvious refinement of prior austenite grains and martensite laths.The microstructure in SZ contains lath martensite with high dislocation density,a lot of nano-sized MX and M_3C phase particles,but almost no M_(23)C_6 precipitates.In thermal mechanically affect zone(TMAZ)and heat affect zone(HAZ),refinement of prior austenite and martensitic laths and partial dissolution of M_(23)C_6 precipitates are obtained at relatively low rotational speed.However,with the increase of heat input,coarsening of martensitic laths,prior austenite grains,and complete dissolution of M_(23)C_6 precipitates are achieved.Impact toughness of SZ at-20?C is slightly lower than that of base material(BM),and exhibits a decreasing trend with the increase of rotational speed.     

Microstructure and mechanical properties of friction stir welded copper

The main objective of this investigation was to apply friction stir welding technique (FSW) for joining of 2 mm thick copper sheet. The defect free weld was obtained at a tool rotational and travel speed of 1,000 rpm and 30 mm/min, respectively. Mechanical and microstructural analysis has been performed to evaluate the characteristics of friction stir welded copper. The microstructure of the weld nugget (WN) consists of fine equiaxed grains. Similarly, the elongated grains in the thermomechanically affected zone (TMAZ) and coarse grains in the heat-affected zone (HAZ) were observed. The hardness values in the WN were higher than the base material. Eventually HAZ shows lowest hardness values because of few coarse grains presence. Friction stir welded copper joints passes 85% weld efficiency as compared to the parent metal.     

Microstructure and mechanical properties of friction spot welded 6061-T4 aluminum alloy

Friction spot welding (FSpW) is a relatively new solid state joining technology developed by GKSS. In the present study, FSpW was applied to join the 6061-T4 aluminum alloy sheet with 2 mm thickness. The microstructure of the weld can be classified into four regions, which are stir zone (SZ), thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ) and the base material (BM), respectively. Meanwhile, defects such as bonding ligament, hook and voids are found in the weld, which are associated to the material flow. The hardness profile of the weld exhibits a W-shaped appearance and the minimum hardness is measured at the boundary of TMAZ and SZ. Both the tensile/shear strength and cross-tension strength reach the maximum of 7117.0 N and 4555.4 N at the welding condition of the rotational speed of 1500 rpm and duration time of 4 s. Compared to cross-tension strength, the tensile/shear strength were stable with the variation of processing parameters. Three different fracture modes are observed under tensile/shear loading, which are plug type fracture, shear fracture and plug-shear fracture. There are also there different fracture modes under cross-tension loading, which are plug type fracture (on the upper sheet), nugget debonding and plug type fracture (on the lower sheet).     

Evaluation of the microstructure and mechanical properties of friction stir welded 6005 aluminum alloy

Abstract

The microstructural change related with the hardness profile has been evaluated for friction stir welded, age hardenable 6005 Al alloy. Frictional heat and plastic flow during friction stir welding created fine and equiaxed grains in the stir zone (SZ), and elongated and recovered grains in the thermomechanically affected zone (TMAZ). The heat affected zone (HAZ), identified only by the hardness result because there is no difference in grain structure compared to the base metal, was formed beside the weld zone. A softened region was formed near the weld zone during the friction stir welding process. The softened region was characterised by the dissolution and coarsening of the strengthening precipitate during friction stir welding. Sound joints in 6005 Al alloys were successfully formed under a wide range of friction stir welding conditions. The maximum tensile strength, obtained at 507 mm min^-1 welding speed and 1600 rev min^-1 tool rotation speed, was 220 MPa, which was 85% of the strength of the base metal.     

Microstructure,mechanical and corrosion properties of friction stir welded high nitrogen nickel-free austenitic stainless steel

Friction stir welding (FSW) was applied to a 2.4 mm thick high nitrogen nickel-free austenitic stainless steel plate using tungsten–rhenium (W–Re) tool. The high-quality weld was successfully produced at a tool rotational speed of 400 rpm and a traveling speed of 100 mm/min. The microstructure, mechanical and corrosion properties of the weld were studied. The nitrogen content of the weld was almost identical to that of base metal (BM). FSW refined grains in the stir zone (SZ) through dynamic recrystallization and led to increase in hardness and tensile strength within the SZ, while the ductility was slightly decreased. The failure of tensile specimens occurred in the BM. TEM results revealed precipitates of Cr₂₃C₆ of size ~ 1 μm in the SZ, although their content was small. The precipitation of Cr₂₃C₆ and increase in δ-ferrite in the SZ led to small decrease in both pitting and intergranular corrosion resistance.     

Effect of Process Parameters on Tensile Strength of Friction Stir Welded Cast LM6 Aluminium Alloy Joints

This paper reports the effect of friction stir welding(FSW)process parameters on tensile strength of cast LM6 aluminium alloy.Joints were made by using dierent combinations of tool rotation speed,welding speed and axial force each at four levels.The quality of weld zone was investigated using macrostructure and microstructure analysis.Tensile strength of the joints were evaluated and correlated with the weld zone hardness and microstructure.The joint fabricated using a rotational speed of 900 r/min,a weldin...     

Fracture toughness of ISO 3183 X80M (API 5L X80) steel friction stir welds

Friction stir welding (FSW) is a solid-state joining process with numerous advantages such as good dimensional stability and repeatability, which is widely used Al alloys and with a great potential for critical joining applications involving high melting temperature alloys. Twelve millimeter thick plates of ISO 3183 X80M (API 5L X80) steel was friction stir welded using two passes on both sides of the plate using ceramic tools. Different heat inputs were obtained using a fix travel (welding) speed in combination with several spindle speeds. The fracture toughness of the two-pass joints was evaluated at 25 °C using the critical crack tip opening displacement (CTOD_m), revealing that joints produced with lower spindle speeds presented higher toughness at the heat-affected zone (HAZ) and stir zone (SZ), which are comparable with the base metal (BM) toughness. On the other hand, joints produced using higher spindle speeds presented low fracture toughness at the SZ and elevated CTOD_m toughness at the HAZ. The joints produced with low spindle speeds showed CTOD_m-values above the offshore standard (DNV-OS-F101) requirements.     

Effect of friction stir welding process parameters on Mg-AZ31B/Al-AA6061 joints

In the present study, dissimilar alloys such as Mg-AZ31B and Al-AA6061 were joined by friction stir welding using different rotational (560, 710, 860 and 1010?rpm) and transverse speeds (16 and 25?mm/min). Metallographic studies (by optical, scanning electron microscope, SEM, and energy dispersive spectrometer, EDS) revealed that the speed parameters mainly influenced the microstructure growth mechanism, which further affects the mechanical properties and corrosion behavior. The combined dynamic action of rotational to transverse speed recrystallized and plasticized the material and produced an alternative lamellar shear band of Al and Mg in the stir zone (SZ). Peak temperature and high rotational speed formed an oxide on the top region and also caused liquation and intermetallic (IMCs) formation. Tensile strength and hardness increased as per the Hall–Petch (fine grains) effect. Higher impact energy was found at moderate rotational and low transverse speeds due to the presence of more soft Al patches. Tensile fractographs showed a river-like pattern, which indicated the brittle nature of the joints. High rotational and high transverse speed illustrated higher tensile strength, while better corrosion resistance was observed in high rotational and low transverse speed.     

Effect of welding parameters on microstructure and mechanical properties of friction stir welded joints of AA7039 aluminum alloy

A high strength Al–Zn–Mg alloy AA7039 was friction stir welded by varying welding and rotary speed of the tool in order to investigate the effect of varying welding parameters on microstructure and mechanical properties. The friction stir welding (FSW) process parameters have great influence on heat input per unit length of weld, hence on temperature profile which in turn governs the microstructure and mechanical properties of welded joints. There exits an optimum combination of welding and rotary speed to produce a sound and defect free joint with microstructure that yields maximum mechanical properties. The mechanical properties increase with decreasing welding speed/ increasing rotary speed i.e. with increasing heat input per unit length of welded joint. The high heat input joints fractured from heat affected zone (HAZ) adjacent to thermo-mechanically affected zone (TMAZ) on advancing side while low heat input joints fractured from weld nugget along zigzag line on advancing side.