Microstructure and wear performance of Al5083/CeO2/SiC mono and hybrid surface composites fabricated by friction stir processing

Friction stir processing (FSP) was utilized to produce surface composites by incorporating nano-sized cerium oxide (CeO₂) and silicon carbide (SiC) particles individually and in combined form into the Al5083 alloy matrix. The study signified the role of these reinforcements on microstructure and wear behavior of the resultant surface composite layers. The wear characteristics of the resultant mono and hybrid surface composite layers were investigated using a pin-on-disc wear tester at room temperature. The microstructural observations of FSPed regions and the worn out surfaces were performed by optical and scanning electron microscopy. Considerable grain refinement and uniform distribution of reinforcement particles were achieved inside the nugget zone. All the composite samples showed higher hardness and wear resistance compared to the base metal. Among the composite samples, the hybrid composite (Al5083/CeO₂/SiC) revealed the highest wear resistance and the lowest friction coefficient, whereas the Al5083/SiC composite exhibited the highest hardness, i.e., 1.5 times as hard as that of the Al5083 base metal. The enhancement in wear behavior of the hybrid composites was attributed to the solid lubrication effect provided by CeO₂ particles. The predominant wear mechanism was identified as severe adhesive in non-composite samples, which changed to abrasive wear and delamination in the presence of reinforcing particles.     

Influence of addition of Grp/Al2O3p with SiCp on wear properties of aluminum alloy 6061-T6 hybrid composites via friction stir processing

Aluminum alloy base surface hybrid composites were fabricated by incorporating with mixture of (SiC+Gr) and (SiC+Al₂O₃) particles of 20 μm in average size on an aluminum alloy 6061-T6 plate using friction stir processing (FSP). Microstructures of both the surface hybrid composites revealed that SiC, Gr and Al₂O₃are uniformly dispersed in the nugget zone (NZ). It was observed that the addition of Gr particles rather than Al₂O₃ particles with SiC particles, decreases the microhardness but immensely increases the dry sliding wear resistance of aluminum alloy 6061-T6 surface hybrid composite. The observed microhardness and wear properties are correlated with microstructures and worn micrographs.     

搅拌摩擦焊工艺参数对2024-T351铝合金搭接焊接头成形质量和力学性能的影响

研究搅拌摩擦焊时R/v比对2024-T351铝合金焊接质量的影响。搅拌摩擦焊时搅拌针的旋转速度设定为750、950和1180 r/min,焊接速度在73~190 mm/min内变化,对应的R/v比在5.00~10.27内。采用各种无损（外观检测、X射线检测）和有损（金相观察、拉伸实验和硬度测量）检测手段对焊接试样进行分析。在所有的试样中,搅拌摩擦焊中各种典型的区域都有存在,不同的区域其晶粒尺寸不同。接头的拉伸性能为基材的52.2%~82.3%。在R/v比为8.06,10.17和10.27时焊接质量最佳。其原因是在最佳搅拌速度下,材料围绕搅拌针充分流动,从而能够填充其中产生的空隙,阻止空洞的生成。结果还表明,R/v 比对接头的硬度分布、洋葱样形状、裂纹的萌生和扩展都有影响。     

T6热处理对SiCp/Al复合材料摩擦磨损性能的影响

采用粉末冶金法制备出不同SiC颗粒体积分数(30%、35%和40%)的SiCp/Al复合材料。采用MMU-5GA微机控制真空高温摩擦磨损试验机对比研究SiCp/Al复合材料在不同体积分数以及T6热处理前后情况下平均摩擦因数和磨损率的变化,通过扫描电镜分析了SiCp/Al复合材料表面磨损形貌,探讨了摩擦磨损机理。试验结果表明,SiC颗粒体积分数在30%~40%变化时,随其体积分数增加耐磨性下降。SiC颗粒体积分数在30%~35%范围内,SiC颗粒与基体结合较好,SiC颗粒作为硬质点起到抵抗磨损和限制基体合金塑性变形产生磨损的双重作用;但SiC含量过多时,颗粒与基体的结合不紧密,磨损时颗粒极易脱落,复合材料耐磨性降低;T6热处理后复合材料的平均摩擦因数和磨损率均降低,这是由于热处理后试样强度及硬度提高,从而提高了试样的耐磨性;常温下复合材料在磨损初期的磨损机理主要以磨粒磨损为主,而在磨损期则为磨粒磨损与剥落磨损共存。     

2024铝合金搅拌摩擦焊接头组织结构及力学性能

采用搅拌摩擦焊工艺实现3 mm厚的2024铝合金焊接,对接头搅拌区的组织结构及力学性能进行分析。研究表明,焊核区主要由再结晶和搅拌的双重影响而形成的细小等轴晶组织构成;热机影响区受焊核区剪切力及热循环的影响,晶粒大小不均匀并伴有晶粒变形的现象。力学性能分析表明,接头显微硬度分布特征与金相组织结构一致;当焊接速度为300 mm/min时,接头的抗拉强度达到294 MPa,为母材的69%,接头的断裂形式为韧窝和沿晶断裂特征的韧性和脆性断裂;接头的焊接残余应力以纵向应力为主,纵向残余应力峰值出现在前进侧轴肩作用的边缘处,焊接速度为300 mm/min时峰值达到164.5 MPa。     

搅拌摩擦焊修复ZL210铸造铝合金组织与性能分析

鉴于铸件中存在不可避免的缺陷,以ZL210合金为研究对象,对搅拌摩擦焊修复技术进行试验研究,重点分析转速对修复接头微观形貌和力学性能的影响. 结果表明,当转速过低时,修复区容易出现孔洞缺陷;在合理的焊接参数组合下可得到无缺陷的焊核区,其由细小的等轴晶组成. 修复区的显微硬度呈“W”分布,热影响区的宽度随转速增加而增加. 另外,随着转速的增加,修复区的抗拉强度先增加后减小;当转速为1 500 r/min,修复区的抗拉强度和断后伸长率达到最大值,分别为318 MPa和11.8%. 断裂形貌表明修复后材料呈现典型的韧性断裂.     

2024-T4铝合金搅拌摩擦焊搅拌区位错及组织性能

采用金相、显微硬度及透射分析方法对2024铝合金搅拌摩擦焊接头搅拌微区的组织性能和位错分布特征进行试验分析,基于位错分析深入了解各微区位错形成与接头组织结构与硬度变化之间的关系。研究表明,WNZ位错主要分布在晶粒内部,大部分是以位错缠结的形式存在,并伴随有大量的沉淀强化析出相Cu_2Mg;而在TMAZ区,大量的位错是以位错塞积的形式存在于晶界或晶粒内部;HAZ区域的位错多以位错塞积的形式存在于晶界附近,并伴随一些典型的Al Cu_3析出相。WNZ和TMAZ区中并未随晶粒细化而造成位错数量和类型的减少,这与FSW特殊的动态回复和动态再结晶过程有关,此外位错分布特征与接头微区硬度分布特征基本吻合。     

Taguchi approach to influence of processing parameters onerosive wear behaviour of Al7034-T6 composites

Taguchi technique was used to predict the influence of processing parameters on the erosive wear behavior Al7034-T6 composite reinforced with SiC and Al₂O₃ particles in different mass fractions. These hybrid metal matrix composites (HMMCs) were fabricated by using a simple technique called stir casting technique. Scanning electron microscope (SEM) was used to study the surface morphology of the composite and its evolution according to processing time. The design of experiment (DOE) based on Taguchi's L₁₆ orthogonal array was used to identify various erosion trials. The most influencing parameter affecting the wear rate was identified. The results indicate that erosion wear rate of this hybrid composite is greatly influenced more by filler content and impact velocity respectively compared to other factors. This also shows the significant wear resistance with the increase in the filler contents of SiC and Al₂O₃ particles, respectively.     

Al_2O_3颗粒增强Al-Mn合金基复合材料的制备及摩擦学性能

采用搅拌铸造法制备了Al2O3颗粒增强Al-2%Mn合金基复合材料,对复合材料的显微组织、硬度和摩擦磨损性能进行了研究。结果表明：复合材料组织由Al基体、δ-Al2O3和MnAl6相组成,且Al2O3颗粒在铝基体中弥散分布。与原始铝基体相比,复合材料的布氏硬度提高了约70%。无论是干摩擦还是SO4.Cl-Na.Ca.Mg型弱碱性水溶液润滑摩擦情况下,复合材料的磨损量均显著低于铝基体。与铝锰合金相比,复合材料具有较低的冲刷腐蚀失重速率。复合材料具有优良的耐磨和耐蚀性。     

Friction and wear properties of mullite／ZrO2／Al2O3 composites

The friction and wear properties of ZrO2 and ALO3 cooperatively toughened mullite composites-mullite/ZrO2/Al2O3(MZA) were studied. The tribological tests were performed in a line-reciprocating tribometer using a GCr15 steel ball on a MZA disk under different dry reciprocating sliding conditions at room temperature. A wide range of normal loads and sliding speeds were chosen to investigate the relationship between the wear mechanisms of MZA and the testing conditions. The wear mechanism diagram of MZA is constructed, it contains two typical regions. It suggests that the wear mechanisms of MZA in each of the region change from one to another depending on the wear conditions. In the mild wear region, the wear rate of MZA is 10^-6 mm^3/m, and the wear mechanism of MZA is plastic deformation accompanied by a little micro-cracking. In the severe wear region, the wear rate of MZA is 10 5 mm^3/m and the dominant wear mechanism in this region is brittle fracture.     

6mm厚6061-T6铝合金双轴肩搅拌摩擦焊工艺方法研究

针对6 mm厚6061-T6铝合金板材,设计制造了不同结构形式和尺寸规格的双轴肩搅拌摩擦焊工具,并对搅拌摩擦焊工具的结构形式和尺寸规格对焊接过程及焊接接头质量的影响进行了系统的分析研究：设计制造了两体式和三体式双轴肩搅拌摩擦焊工具,并对两种结构形式进行分析;设计制造了环状轴肩和凹面轴肩,通过焊接工艺试验得知凹面轴肩焊缝成形性优于环状轴肩;设计制造了正-反螺纹搅拌针、正螺纹搅拌针、整圆柱搅拌针和圆柱铣扁搅拌针;圆柱铣扁搅拌针焊缝焊接质量优于其他三种结构形式的搅拌针。采用凹面轴肩和圆柱铣扁搅拌针组装成的搅拌头,对6 mm厚6061-T6铝合金板材进行焊接,在主轴转速为800 r/min、焊接速度为150 mm/min工艺参数下,焊接接头得到最大抗拉强度值为220MPa,达到母材抗拉强度（315 MPa）的70%。     

2024铝合金板搅拌摩擦焊接塑性材料流动的可视化检测与数值模拟(英文)

将薄铜片作为标示材料镶嵌于2024铝合金板中,经搅拌摩擦焊接焊后,用金相法观察其最终位置。参考材料流动的可视化实验结果,建立搅拌摩擦焊传热与材料流动的三维数值分析模型。搅拌针附近塑性材料流动速度分布模式的计算结果与可视化实验结果基本一致。当焊接速度一定时,随搅拌针旋转速度的提高,搅拌针附近塑性材料流动加剧。焊核区形状与尺寸的计算结果与实测数据吻合。     

钼酸钠对2024铝合金及搅拌摩擦焊焊缝缓蚀效率的影响

通过搅拌摩擦焊（FSW）手段,制备出2024铝合金同种焊接接头.在室温0.2mol/L NaHSO3和0.6 mol/L NaCl混合溶液中,添加不同浓度的钼酸钠,通过静态失重法、动电位极化曲线以及交流阻抗谱（EIS）测试,评价了室温下此缓蚀剂对2024母材及其搅拌摩擦焊焊缝的电化学行为的影响.结果表明,焊缝的缓蚀效率要优于母材的缓蚀效率,且随浓度增加而增加,钼酸钠是一种有效的阳极钝化型缓蚀剂,并且其缓蚀作用效果和金属表面状态密切相关.     

Effect of corrosive environment on fatigue property and crack propagation behavior of Al 2024 friction stir weld

In this investigation, 2024 aluminium alloy plates were friction stir welded, a sequence of experiments was performed including fatigue and crack propagation tests in air, under pre-corrosion and in a 3.5% NaCl solution, in combination with fractography analyses of near-threshold region, Paris region and finial fracture region with the aid of scanning electron microscopy (SEM). Results showed that the corrosive environment caused a dramatical decrease in fatigue lives of FS welds, the corrosion fatigue lives of FS welds were almost a half of those of the as-welded specimens. The crack growth rates in FS welds were higher than their counterparts in base materials, under the corrosive environment, the crack growth rate differences between base materials and FS welds become increasingly apparent with the increase of stress intensity factor range ΔK, but the pre-corrosion process had little effect on the FS welds' crack propagation behavior except for shortening the crack initiation lives greatly.     

2024铝合金粉末选区激光熔化成形工艺研究

采用自主研发的金属增材制造设备对2024铝合金粉末进行了选区激光熔化成形,研究了不同工艺参数下该合金的显微组织及室温拉伸性能。结果表明,激光功率为260 W,扫描速度900 mm/s,扫描间隔0.12 mm时,2024铝合金显微组织细小,结构致密,抗拉强度为372 MPa,伸长率为6.1%,具有较高的室温力学性能。     

LF2铝合金搅拌摩擦焊接接头磨损性能研究

试验了LF2铝合金搅拌摩擦焊接接头的摩擦磨损行为，通过观察接头磨损表面形貌没有发现明显的大块剥落开裂迹象。表面呈现疲劳磨损特征。这是由于搅拌摩擦焊接头形成的细小等轴晶粒导致裂纹扩展困难所造成的。     

Casting fabrication of in situ Al3Ti-Al composites and their wear behaviors

The Al3li intermetallic reinforced pure Al, Al-13Si and Al-17Cu matrix composites were prepared by casting method. Their microstructures and dry sliding wear behaviors at room temperature and 100℃ were particularly investigated. The results indicated that the Al3Ti phases in these composites were all in flaky form. But the aspect ratio of the Al3Ti platelets decreased with the increase of Ti content in the pure AI, Al-Cu and Al-Si matrix composites, in order of effectiveness. The effect of Si on the Al3Ti morphology seemed to be greater than that of Cu. The distributions of the Al3Ti platelets were different in the different matrix composites, leading to different grain refining effects. Except for the sub-wear regime of adhesive wear, the plastic deformation induced wear was a dominant wear mechanism for all of the composites at room temperature and 100℃. Increasing the testing temperature, decreasing the Al3Ti content or the hardness of materials could enhance these two wear mechanisms, and thus increase the wear rate. The Al-Cu matrix composite had the best wear resistance, while the pure Al matrix composite showed the worst for the same Ti content. These differences or changes were attributed to the differences in materials' hardness or the strengthening effects of the Al3Ti platelets.     

Dry friction and wear characteristics of MoSi2 against ahoy steels

The dry friction and wear characteristics of three kinds of friction couples under different loads, MoSi2/45 tempered steel, MoSi2/45 quenched steel, and MoSi2/CrWMn steel, were investigated by using a friction and wear tester. SEM and X-ray diffraction were employed to analyze the microphotograph of the worn surface and the phase of worn pieces in order to reveal the wear mechanisms of MoSi2 material. The results show that MoSi2/CrWMn steel friction pair has good dry friction and wear properties under the load of 80 N, where the friction coefficient is 0.255 and the wear rate of MoSi2 is only 14.72 mg.km-1. But under the load of 150 N, it is MoSi2/45 tempered steel friction pair that has good tribological properties,MoSi2 under low loads is brittle fracture. With the increase of load, the main wear mechanism of MoSi2 against 45 quenched steel or CrWMn steel is adhesive wear. However, the wear mechanism of MoSi2 against 45 tempered steel is changed from oxidation-fatigue wear to adhesive wear.     

Dry friction and wear characteristics of MoSi2 against alloy steels

The dry friction and wear characteristics of three kinds of friction couples under different loads, MoSi2/45 tempered steel, MoSi2/45 quenched steel, and MoSi2/CrWMn steel, were investigated by using a friction and wear     

聚四氟乙烯对搅拌摩擦加工制备Al-Ni复合材料均匀性的影响

采用搅拌摩擦加工技术制备了Al-Ni系金属间化合物增强铝基复合材料,通过SEM、XRD对复合材料的微观结构及相组成进行了分析,研究在原材料中添加聚四氟乙烯对搅拌摩擦加工制备复合材料中增强相含量及分布均匀性的影响,并对增强相形成的物理模型进行了探讨。结果表明:添加聚四氟乙烯可以显著改善Al-Ni复合材料的均匀性;加入聚四氟乙烯后会阻隔Ni粉的团聚,致使Ni与Al的接触面增大,从而增大了Ni与Al的反应界面,导致反应程度增大,Al_3Ni金属间化合物生成量增多。