焊接参数对7A04铝合金搅拌摩擦焊接头组织与力学性能的影响

采用不同的焊接参数对3 mm厚7A04铝合金板进行焊接,并对接头的组织、沉淀相、力学性能及断口形貌进行了分析. 结果表明,焊核区组织发生动态再结晶,形成细小的等轴晶粒,热影响区晶粒发生明显粗化. TEM分析结果显示,经搅拌摩擦焊后,焊核区部分沉淀相溶解. 焊核区晶粒尺寸随焊接速度增大而减小. 当焊接速度为120 mm/min,旋转速度为800 r/min时,接头强度达到最大值 454.2 MPa,为母材的95%,断后伸长率为3.97%,为母材的70%. 硬度测试显示搅拌摩擦焊接头发生软化,焊缝区域硬度低于母材,硬度值最低点出现在热影响区;拉伸断口形貌SEM图像表明接头断裂方式为韧性和脆性混合型断裂.     

FSW焊接AZ31镁合金板材接头组织与性能分析

选用Al-Zn-Mn-Mg系镁合金板材进行搅拌摩擦焊接,分析其接头显微组织及沉淀相演变规律。由于温度和变形程度不同,搅拌区不同位置的组织有所不同,焊核区组织是细小、均匀的等轴晶,存在圆片状和棒状沉淀相;热机影响区晶粒局部较细小,有明显变形,圆片状和棒状沉淀相中镁含量降低,铝含量增加;热影响区晶粒部分细小,部分长大,晶粒大小不均;母材呈典型的轧制组织。整体区域硬度变化不大,与母材区比略有下降。     

低活化铁素体–马氏体钢搅拌摩擦焊接头组织和性能分析

文中对9% Cr低活化铁素体-马氏体钢搅拌摩擦焊接头的组织和性能进行了分析.结果表明,搅拌摩擦焊接头不同区域微观组织存在明显的差异.搅拌区内奥氏体的动态再结晶引起晶粒细化和马氏体转变,并且晶界M₂₃C₆相溶解,晶内M₃C相析出;热力影响区组织变化与搅拌区相似,但晶粒尺寸明显大于母材;热影响区和母材区均表现回火组织特征.搅拌区硬度显著提高,分布均匀;热力影响区硬度值变化较大;热影响区发生软化,其硬度值在接头区域最低.随着拉伸测试温度的增加,搅拌区的屈服强度单调降低,抗拉强度先增大后减小,而断后伸长率先减小后增大.     

2219-O铝合金的搅拌摩擦焊接

对2219-O铝合金进行了搅拌摩擦焊接,采用光学显微镜分析了接头的微观组织,采用拉伸试验方法评价了接头的力学性能.微观分析表明,在热机循环的共同作用下,焊核区(WNZ)发生了动态再结晶,形成了细小的等轴晶粒,并且沉淀相的数量较其它各区有所增加;热机影响区(TMAZ)晶粒被拉长、弯曲,发生了动态回复和部分再结晶,晶粒内部开始有新的晶粒生成;热影响区(HAZ)的晶粒发生粗化.力学性能测试结果表明,当转速为800r/min,焊接速度为200～400 mm/min时,接头与母材等强度,断裂发生在母材区;当焊接速度大于400mm/min时,接头的抗拉强度很低,断裂发生在缺陷处.     

低碳钢与紫铜搅拌摩擦焊接头显微组织分析

用搅拌摩擦焊焊接了4 mm厚的Q235低碳钢板和T2紫铜板,得到了内部无缺陷、外观成形良好、无变形的对接接头.研究表明,低碳钢紫铜接头的显微组织与其所受到的热和力作用大小有关.在接头钢侧,轴肩挤压区有较大的变形,组织发生动态再结晶后形成了细小的等轴晶铁素体;在探针附近的热影响区,经历的应变较小,组织则由变形的先共析铁素体和侧板条铁素体组成.在接头铜侧热影响区的晶粒受热长大,而热力影响区的铜由于发生了动态再结晶,晶粒细小.在焊核区,上部主要由钢、铜薄层交叠组成;焊核中下部为钢、铜及钢与铜形成的化合物交叠组成的漩涡状条带,其中铜条带的组织为细小的等轴晶,钢条带的组织为细小的等轴晶或先共析铁素体 侧板条铁素体组织.     

船用铜合金搅拌摩擦焊研究

针对典型的船用铜合金开展了搅拌摩擦焊试验研究,通过金相显微镜、投射电子显微镜和能谱分析观察研究了焊缝的组织形貌,通过显微硬度、拉伸性能试验测试了接头的力学性能。结果表明,采用搅拌摩擦焊可以得到性能良好的船用铜合金焊缝。接头焊核区由均匀细小的等轴晶粒组成,顶锻区、热机影响区的等轴晶由于摩擦热作用晶粒有所增大,热影响区晶粒受热长大。焊核晶粒发生动态再结晶,得到细晶强化,同时强化相细小分布均匀,实现了弥散强化。焊缝厚度方向硬度比较均匀,没有明显的软化区,水平方向硬度从焊核到母材逐渐降低。接头抗拉强度与母材相当,屈服强度高于母材。     

6061-T651铝合金搅拌摩擦焊接头的显微组织和力学性能

通过金相显微镜观察、硬度测试、拉伸试验和扫描电镜观察等试验手段研究分析了6061-T651铝合金搅拌摩擦焊接头的微观组织与力学性能。结果表明,接头处焊核区因剧烈塑性变形和高温循环而发生了动态再结晶,形成细小的等轴晶组织,而热影响区晶粒组织和第二相颗粒均发生一定的粗化。接头的硬度沿着垂直于焊接方向基本呈W形分布,热影响区由于晶粒粗化以及第二相颗粒的聚集长大,其硬度值最低。沿垂直于焊接方向和平行于焊接方向的接头试样强度都比母材低,沿垂直于焊接方向的接头试样伸长率低于母材,而平行于焊接方向的伸长率比母材的高;断口形貌表明断裂方式为典型的韧性断裂。     

焊接速度对7A04铝合金搅拌摩擦焊接头组织与性能的影响

采用不同焊接速度焊接7A04铝合金板材,并对搅拌摩擦焊接头进行微观组织和力学性能分析研究。结果表明,接头焊核区由于搅拌头的搅拌作用及发生动态再结晶,形成细小等轴晶,尺寸远小于母材;机械热影响区处于搅拌头外缘,在搅拌头搅拌作用下发生明显的拉伸变形;热影响区晶粒发生明显粗化。不同焊接速度下焊缝区的硬度分布整体上呈"W"形分布,接头软化,焊缝区硬度低于母材,硬度最高值出现焊核区,最低值出现在热影响区。当旋转速度为800 r/min,焊接速度为120 mm/min时,接头成型性最佳,其抗拉强度为410 MPa,达母材强度的75%。     

汽车吸能盒用铝合金搅拌摩擦焊工艺研究

试验采用搅拌摩擦焊对汽车吸能盒用6008铝合金进行焊接试验。结果表明：在旋转速度为1400 r·min^-1、焊接速度为700 mm·min^-1时,焊接接头性能最佳,平均抗拉强度为209.3 MPa,可达到母材实际抗拉强度的85.74%;各参数下搅拌摩擦焊接头外观均无明显缺陷,可满足实际生产要求;焊缝截面整体形貌呈倒圆锥形,焊核区材料发生完全动态再结晶及长大形成细小的等轴再结晶组织。热机影响区晶粒发生较大程度的弯曲变形及部分长大现象。热影响区组织发生少量晶粒长大现象,总体上与原始母材组织形貌相差不大。     

7075铝合金板搅拌摩擦焊接头再结晶过程研究

针对7075铝合金板搅拌摩擦焊对接接头组织变化过程及搅拌头下压深度对焊接过程中焊缝塑性金属流动行为进行研究。研究结果表明:焊核区金属发生了动态再结晶,由细小的等轴晶组成;热机影响区晶粒出现弯曲变形,并发生了动态回复与部分再结晶;热影响区晶粒没有发生明显长大,晶粒间界随着热输入增大而加宽。搅拌摩擦焊接过程中,焊缝塑化金属存在三种运动,表层的水平圆周运动,探针周围的无序运动,底层的向上运动。     

Microstructures and ion-irradiation behaviour of friction stir welded 12Cr-ODS steel

12Cr oxide dispersion strengthened steel was successfully joined by friction stir welding (FSW), and the joints were irradiated with 3?MeV Au ions at 500°C. The morphology of grains, dislocations, sizes and distributions of nano-sized oxide particles (NPs) in different zones of the FSW joints were analysed. It was found severe plastic deformation occurred and fine equixed grains were formed in stir zone (SZ). The NPs coarsen obviously in thermal-mechanically affected zone (TMAZ) on advancing side (AS) due to the relative movements of plastic materials with high-velocity gradient. The size distributions of the NPs in base metal (BM), heat affected zone (HAZ) and RS-TMAZ are concentrated in a smaller range than those in SZ and AS-TMAZ. Finer grains and high density of dislocations result in hardness increasing obviously in SZ. Irradiation introduced higher hardening in HAZ because of its less grain boundaries and dislocation density compared with SZ and BM.     

Relationship Between Microstructures and Microhardness in High-Speed Friction Stir Welding of AA6005A-T6 Aluminum Hollow Extrusions

AA6005 A-T6 aluminum hollow extrusions were friction stir welded at a fixed high welding speed of 2000 mm/min and various rotation speeds. The results showed that the heat-aff ected zone(HAZ) retained the similar grain structure as the base material except some grain coarsening, and the density of dislocations and β′ precipitates were almost unchanged, indicating that the high welding speed inhibited the coarsening and dissolution of β″ precipitates via fast cooling rate. The thermo-mechanically aff ected zone(TMAZ) was characterized by elongated and rotated grains, in which a low density of β′ precipitates and the highest density of dislocations were observed. The highest heat input and severest plastic deformation occurring in the nugget zone(NZ) resulted in the occurrence of dynamic recrystallization and a high density of dislocations. Hence, all the β″ precipitates and most of the β′ precipitates dissolved into the matrix, and a few β′ precipitates were transformed into β precipitates. The microhardness was controlled by the precipitation and solution strengthening in the HAZ, by the dislocation and precipitation strengthening in the TMAZ, and by the fine-grain and dislocation strengthening in the NZ. With the increase in rotation speed, the peak and the lowest microhardness value increased monotonously.     

放电等离子体烧结技术制备过共晶Al-Si-Fe粉末冶金合金的显微组织和压缩变形行为

Al-Si-Fe基铝合金材料由于具有高耐磨性、低密度以及低热膨胀性能,因而主要用于汽车发动机部件。利用气体雾化粉末,采用放电等离子体烧结技术制备Al-17Si-5Fe-2Cu-1Mg-1Ni-1Zr合金。所制备材料的晶粒尺寸为530nm,并且观察到细等轴晶粒和均匀分布的析出物。研究了放电等离子体烧结技术制备的材料在不同温度和应变速率下的压缩变形行为。结果表明,所有的真应力一真应变曲线在达到峰值应力后呈稳态流动趋势,随着测试温度的升高和应变速率的降低,峰值应力呈下降趋势。在变形样品中,观察到了等轴晶粒和等轴晶粒中的位错结构。这些现象说明,合金在高温变形过程中发生了动态再结晶。     

Recrystallization and microstructural evolution during hot extrusion of Mg97Y2Zn1 alloy

This study revealed that the extrusion temperature has a great influence on microstructure and mechanical properties of the Mg₉₇Y₂Zn₁ alloy. The average grain sizes increased from 3 μm to 8 μm with increasing extrusion temperatures from 623K to 773 K. Both dynamic recrystallization (DRX) and static recrystallization (SRX), which occur during and after deformation, respectively, were observed. The alloy, which extruded at a relatively high temperature, exhibited lower strength because the strain strengthening was balanced by the softening that originated from DRX. Three types of morphologies, namely, big recrystallized grains, fine recrystallized grains, and non-recrystallized grains, were observed in the extruded microstructures obtained at 623 K. The dislocation density was quite high in the fully recrystallized grain. The extruded microstructures obtained at 773 K were composed of large grains with more uniform size. Their degree of recrystallization was higher and the dislocation density also declined. All dislocation in the grain were distinguished as 〈c+a〉 dislocations. Submicron scale precipitates were distributed along the newly formed recrystallized grain boundaries and had a remarkable pinning effect on the recrystallized grain growth after extrusion at 773 K. The precipitates can be divided into two main types: mixed type and single type.     

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.     

3003-H16铝合金卷材生产过程中的组织演变

利用热分析仪、光学显微镜、扫描电镜和能谱仪等方法研究了3003-H16铝合金卷材生产过程中的组织演变。结果表明,晶粒尺寸、二次枝晶间距和金属间化合物尺寸从铸锭心部至铸锭表层逐渐减小。当均匀化温度为590 ℃时,α-Al晶体内析出细小颗粒状的Al₆Mn;随均匀化温度的提高,颗粒状析出相不断溶解并促进针棒状析出相长大;当均匀化温度为640 ℃时,针棒状析出相开始溶解,至650 ℃时完全溶解。金属间化合物Al₆(Fe,Mn)和Al₆Mn随均匀化温度的升高而变得圆滑球化,部分Al₆(Fe,Mn)在均匀化过程中转变为Al(Fe,Mn)Si。3003铝合金热轧卷材的晶粒组织在厚度方向上存在不均匀性,冷轧和中间退火后有所改善。3003铝合金卷材中的化合物沿轧制方向成行排列,具有明显的方向性,其中大尺寸化合物的比例随加工率的增大逐渐降低。均匀化可以改善3003铝合金的成分和组织均匀性,改善合金的塑性。变形加工在提高3003铝合金强度的同时降低了合金的塑性。中间退火过程中纤维状的变形组织转变为再结晶组织,消除了硬化现象,合金的塑性得到改善。     

Microstructure and Mechanical Properties of Selective Laser Melted Al-2.51Mn-2.71Mg-0.55Sc-0.29Cu-0.31Zn Alloy Designed by Supersaturated Solid Solution

Selective laser melting (SLM) of aluminium alloys for lightweight application is arousing widespread interest, but the available alloy compositions are limited due to unsatisfactory mechanical performances. The rapid solidification of SLM provides a pathway to design a novel alloy composition with extended solubility. This strategy is demonstrated by an additively manufactured novel Al-2.51Mn-2.71Mg-0.55Sc-0.29Cu-0.31Zn alloy with the supersaturated solid solution in the present study. The microstructure of as-build sample is characterized with multi-modal grains with the fine equiaxed grain (FEG, ~ 800 nm) at molten pool boundaries, coarse equiaxed grain (CEG, ~ 2 μm) and columnar dendrites (CD, ~ 4 μm) inside the molten pool, which relates to the precipitations type and distribution. It is observable that Al₃(Sc, Zr) precipitation particles with the size of ~ 50 nm are dispersed in the FEG zone, while the interior of CEG shows no Al₃(Sc, Zr) particle which only exists at the CEG boundaries. Regardless of FEG, CEG or CD, the slender Al₆Mn precipitation with the length of ~ 500 nm is distributed along the grain boundaries. Meanwhile, a lot of vacancies and thickness fringes are detected in the FEG zone, which confirms the supersaturated solid solution in laser rapid solidification. The ultimate tensile strength and yield strength of the as-printed sample are ~ 380 MPa and ~ 330 MPa, respectively, with elongation ~ 14%, which increase to ~ 440 MPa and ~ 410 MPa with a reduction of elongation to ~ 9% after heat treatment.     

Microstructure control and high temperature properties of TiAl base alloys

An equiaxed fine grain structure, a γ grain structure with the precipitated ₂ laths, and a fully lamellar structure were obtained by the microstructure control using thermomechanical processing and heat treatment. The key to obtaining the equiaxed fine grain structure using isothermal forging is to decompose the lamellar structure and then produce the fine grain microstructure through dynamic recrystallization. TiAl base alloys consisting of fine equiaxed grains, in particular, Ti-39Al-9V consisting of the γ and B2 phases exhibited superplastic elongation of more than 600% at 1423 K. Creep rupture properties of TiAl binary alloys with various microstructures were studied in purified He in the temperature range from 1073 to 1373 K. Above 1173 K the precipitated ₂ phase improved the steady state creep rate and creep life. At 1023 K, the ₂ phase did not improve the creep rate, although the steady state creep rate decreased and the creep life increased as the γ grain size increased.     

Cu-Cr-Zr合金连续驱动摩擦焊接头热力演变

采用热电偶—蓝牙技术测量了Cu-Cr-Zr合金连续驱动摩擦焊接头特征点的温度,并研究接头温度与组织演变的关系. 结果表明,各特征点温度均存在一定程度的滞后现象;沿工件径向, 2/3R区温度最高;沿工件轴向,摩擦界面处温度最高;旋转工件的温度略低于移动工件. 在热力耦合作用下,接头焊合区形成细小的等轴晶粒,热力影响区晶粒被不同程度拉长,呈塑性流线.从轴心到外径动态再结晶区的宽度增加,晶粒粗化,而与其相邻的热力影响区径向塑性流动的趋势减小. 此外,与旋转端相比,移动端接头具有较高的峰值温度和再结晶峰值宽度,所对应的焊合区晶粒也较为粗大.