多次搅拌下SiC颗粒增强铝基复合层组织与性能

采用搅拌摩擦加工制备SiC颗粒增强铝基复合材料,研究搅拌次数对复合层晶粒尺寸、硬度、拉伸及磨损性能的影响。结果表明,搅拌加工时添加SiC颗粒可提高复合层的硬度、耐磨性,但会降低其强度。随着搅拌次数的增加,复合材料硬度得到提高,添加SiC颗粒的试样经4道次搅拌后搅拌区平均硬度130 HV,而未添加颗粒时为118 HV。添加颗粒试样搅拌4次后,抗拉强度比搅拌1次试样强度明显提高,可达360.6 MPa,可达铝合金母材的68.5%。添加颗粒能够提高复合层的耐磨性,未添加颗粒时复合层摩擦系数为0.6,相比添加颗粒时仅为0.5。随着搅拌次数的增加,搅拌区晶粒细化程度得以提高,SiC颗粒分布更加均匀。     

搅拌摩擦加工SiC复合层对镁合金摩擦磨损性能的影响

研究了搅拌摩擦加工（FSP）AZ91D镁合金SiC复合层的微观组织和磨损性能。结果表明,复合层SiC粒子分布均匀,晶粒细小,成分均一,抗摩擦磨损性能较基体有大幅度提高。     

搅拌摩擦加工制备镁基铝覆层材料的组织与性能

在采用多道次搅拌摩擦加工成功地在镁合金表面覆合一层铝层的基础上,利用光学显微镜、透射电子显微镜、扫描电子显微镜、能谱分析和电子万能材料试验机对界面组织、元素成分分布、界面结合力和断口形貌进行了分析,并分析了不同焊接速度对重叠区界面组织和性能的影响规律.结果表明,界面由N道次区、重叠区和N+1道次区组成,重叠区界面过渡层的厚度随着焊接速度的降低而增加.其过渡层由Al+Al₃Mg₂相和Mg+Al₁₂Mg₁₇相组成.重叠区界面的剪切力随着速度的降低而增加,断裂方式为塑性断裂.     

Machining characteristics of fine grained AZ91 Mg alloy processed by friction stir processing

AZ91 Mg alloy was considered and friction stir processing (FSP) was adopted to achieve grain refinement to investigate the effect of grain size and secondary phase on machining characteristics during drilling at various speeds and feeds. Super saturated AZ91 Mg alloy was obtained after FSP and the grain refinement was achieved from (166.5±8.7) µm to (21.7±13.5) µm. Surprisingly, hardness reduced for FSP AZ91 Mg alloy (88.95±6.1) compared with AZ91 alloy (108.2±15.6), which was attributed to the reduced secondary phase. However, the mean cutting force for FSP-treated (FSPed) AZ91 Mg alloy was marginally increased. The edge damage of the drilled holes was lower for FSPed AZ91 Mg alloy compared with unprocessed AZ91 Mg alloy. Hence, it can be understood that the grain refinement may slightly increase the cutting forces during drilling but better edge finishing can be achieved in machining of AZ91 Mg alloy.     

Processing and mechanical properties of SiC particulate reinforced AZ91 composites fabricated by stir casting

The influence of stirring parameters （stirring temperature, stirring speed and stirring time） on the particle distribution of 10%（volume fraction） SiC particulate reinforced AZ91 composites （SiCp/AZ91） was studied. It is found that it is necessary for 10μm SiC particulate reinforced AZ91 composites to stir the molten composites in semi-solid condition with vortex formation, or else the cluster of the reinforcements would not be eliminated. Compared with the monolithic alloy, the SiCp/AZ91 composite has higher strength, especially for yield strength, but the elongation is reduced. For the as-cast composite, the particles often segregate within the grain boundary regions. Extrusion can effectively reduce the segregation of SiC particles and improve the mechanical properties of the composite. The extrusion-induced reduction in particle size varies with extrusion temperatures and extrusion ratios. The effect of extrusion-induced reduction in particle size on the mechanical properties of the composites is not always beneficial.     

纳米SiC颗粒增强AZ91D复合材料的制备及性能

利用高能超声辅助法制备纳米SiC颗粒(n-SiCp)增强AZ91D镁基复合材料(n-SiCp/AZ91D),并对其显微结构和室温力学性能进行测试分析。结果表明:纳米SiC颗粒的加入能够起到细化晶粒的作用,纳米颗粒在基体中的分布比较均匀,超声波辅助技术能够有效地分散纳米颗粒,在重力铸造下所制备的复合材料的抗拉强度、屈服强度和硬度均高于基体,尤其是屈服强度较基体提高了57%。     

Effect of Friction Stir Processing on Microstructure and Mechanical Properties of Cast AZ31 Magnesium Alloy

对铸态AZ31镁合金进行单道次和双道次搅拌摩擦加工,对其微观组织和力学性能进行研究.结果表明:铸态AZ31镁合金搅拌摩擦加工后,共晶网状β-Mg17Al12相破碎并发生固溶,微观组织显著细化和均匀化.AZ31镁合金母材和单道次搅拌摩擦加工后的试样没有择优取向,而双道次搅拌摩擦加工后的试样存在择优取向,其(0002)基平面与试样表面平行.单道次和双道次搅拌摩擦加工后试样的抗拉强度分别提高了43和82MPa,延伸率提高了4.3％和11.9％.搅拌摩擦加工后试样的拉伸断口表现为韧性断裂特征.     

Enhanced corrosion behavior and mechanical properties of AZ91 magnesium alloy developed by ultrasonic-assisted friction stir processing

In this study, ultrasonic-assisted friction stir processing (UaFSP) and friction stir processing (FSP) were conducted on AZ91 magnesium alloy sheets, and their microstructure, corrosion behavior, and mechanical properties were comparatively investigated. Scanning electron microscopy, open-circuit potential, and potentiodynamic polarization were used to study the corrosion behavior of the material. Electrochemical measurements reveal that employing UaFSP, the corrosion rate of the AZ91 magnesium alloy was significantly reduced where lower corrosion current density for UaFSP specimens was obtained (2.09 µA/cm²) compared with 3.42 µA/cm² for the FSP and 6.82 µA/cm² for the base metal. This is mainly attributed to the alteration of morphology and better distribution of the β-Mg₁₇Al₁₂ phase during UaFSP. By using ultrasonic vibration in FSP, a finer grain structure was obtained, which improved the tensile strength and hardness of the AZ91 Mg alloy.     

搅拌摩擦加工工具对镍铝青铜合金显微组织和机械性能的影响

目的掌握搅拌摩擦加工镍铝青铜合金的组织演变规律,获得机械性能最好的显微组织。方法基于搅拌摩擦加工热输入理论改善加工工具,采用改善前后的工具制备具有各种微观组织的镍铝青铜合金,并采用显微硬度仪测试合金的显微硬度,通过光学显微镜、扫描电子显微镜、透射电子显微镜观察加工合金的显微组织。结果搅拌摩擦加工的组织主要包括魏氏体α、带状α、溪流状α以及等轴状α组织,各组织形成的最高温度逐渐减小,其中等轴状组织具有最高的显微硬度,其微观组织主要包括大量的等轴状α晶粒、κ相和极少的β′相。结论通过减少工具轴肩直径,增加搅拌针的长度来改善加工工具,可以明显减少搅拌摩擦加工过程中的热输入。较低最高温度下制备的等轴状α组织具有最好的机械性能,其主要的强化机制为细晶强化、第二相强化和加工硬化。     

超声振动对6061-T4铝合金搅拌摩擦焊接头组织和性能的影响

利用自主研制的试验装置,通过工具头将超声振动能量施加在搅拌头前方的待焊工件上,研究了超声振动能量对减少焊接缺陷、改善搅拌摩擦焊接头组织和力学性能的影响.对6 mm厚度6061-T4铝合金板进行了超声振动强化搅拌摩擦焊工艺试验,并与相同工艺条件下的常规搅拌摩擦焊进行了对比.结果表明,超声振动能够减小焊速/转速比较大时的焊缝内部隧道型缺陷,增大材料对接混合区宽度和焊核区体积,细化焊核区和热力影响区微观组织,提高接头抗拉强度和焊核区显微硬度.     

超声振动对6061-T4铝合金搅拌摩擦焊接头组织和性能的影响

利用自主研制的试验装置,通过工具头将超声振动能量施加在搅拌头前方的待焊工件上,研究了超声振动能量对减少焊接缺陷、改善搅拌摩擦焊接头组织和力学性能的影响.对6 mm厚度6061-T4铝合金板进行了超声振动强化搅拌摩擦焊工艺试验,并与相同工艺条件下的常规搅拌摩擦焊进行了对比.结果表明,超声振动能够减小焊速/转速比较大时的焊缝内部隧道型缺陷,增大材料对接混合区宽度和焊核区体积,细化焊核区和热力影响区微观组织,提高接头抗拉强度和焊核区显微硬度.     

超声振动制备流变铸造AZ91镁合金浆料的微观组织和性能

研究AZ91镁合金流变铸造的微观组织和力学性能。采用超声振动方法和压铸成型制备镁合金半固态浆料。结果表明：由于超声振动的空化、声流效应,在成核阶段获得细小圆整的初生a-Mg颗粒;随着超声振动时问延长,初生a-Mg颗粒的固相体积分数和平均尺寸增大,但形状系数基本不变,为0．7;在液相线以下温度附近超声振动6min可获得最佳的AZ91镁合金半固态浆料,其压铸后的拉伸强度和伸长率分别是248MPa和7．4％。流变铸造AZ91镁合金的断裂机制是韧性断裂。     

搅拌摩擦加工铸态AZ31镁合金组织与性能研究

采用搅拌摩擦加工技术对铸态AZ31镁合金进行单道次加工,研究加工区域的微观组织和力学性能。结果表明：搅拌摩擦加工过程中,材料发生了剧烈的塑性变形,粗大的β-Mg17Al12相显著破碎,形成细小、均匀的再结晶组织。XRD分析表明,搅拌摩擦加工导致大量的β相固溶到镁合金基体中,产生固溶强化作用。搅拌摩擦加工后的试样平均HV硬度值为810 MPa,高于铸态AZ31镁合金的硬度值,抗拉强度比铸态AZ31镁合金提高43 MPa,延伸率提高4.3%,拉伸断口表现为微孔聚合剪切断裂特征。     

冷却条件对超声振动法制备AZ91半固态浆料组织的影响(英文)

利用超声振动法制备AZ91合金半固态浆料,在不同温度区间和冷却速率下对熔体进行超声处理,研究冷却条件对AZ91半固态浆料微观组织的影响。结果表明:在形核阶段,熔体在超声振动引发的空化和声流效应作用下,能够获得细小、近球状的初生α-Mg固相颗粒;在固液相线温度区间内,随着超声温度下限的降低,半固态浆料的固相率和固相颗粒的平均尺寸增加;在超声振动过程中,随着冷却速率的提高,半固态浆料的固相率增大,固相颗粒的平均形状因子降低。在本实验条件下,适宜的超声振动温度区间为605°C到595°C或590°C,合适的冷却速率为2~3°C/min。     

强制冷却搅拌摩擦加工2024铝合金的组织性能研究

在强制冷却条件下对2024-T4铝合金板进行搅拌摩擦加工,分析了各区(母材区、热机影响区、搅拌区)的组织形貌特征,并研究了前进速度对加工区组织性能的影响。结果表明,从母材、热机影响区到搅拌区晶粒逐渐减小,搅拌区为均匀细小的再结晶组织,平均晶粒尺寸达1.9μm;母材大部分为大角度晶界,热机影响区主要为小角度晶界,搅拌区取向差分布呈双峰模态。搅拌区硬度和抗拉强度随前进速度增大而增大。     

粉末粒度对FSP制备Al-Ni金属间化合物增强铝基复合材料的影响

采用搅拌摩擦加工法在Al基体中添加粒度30~40μm,8~10μm,2~3μm的Ni粉,制备Ni(400)/Al、Ni(1500)/Al及Ni(6500)/Al复合材料。采用SEM、EDS以及XRD对复合区微观结构及相组成进行分析。结果表明,Ni粉粉末粒度对生成的产物形态有较大影响,随着粉末尺寸增大,团聚效应减弱,破碎效果增强,Ni(6500)/Al、Ni(1500)/Al和Ni(400)/Al中Ni团体依次呈独特叠层状组织、类椭圆形结构和近圆形结构;粉末尺寸的增大对金属间化合物的生成更有利;与基体相比,Ni(6500)/Al、Ni(1500)/Al和Ni(400)/Al的抗拉强度依次提高了50%、59%和71.9%。     

Effect of rotation speed on microstructure and mechanical properties of bobbin tool friction stir welded AZ61 magnesium alloy

The 5-mm-thick AZ61 magnesium alloy was friction stir welded by using the specially designed bobbin tool with various rotation speeds. Defect-free welds were successfully obtained with rotation speed ranging from 550 to 600?rev?min^?1. Grain size in different regions of the joints varied depending on the rotation speed. The hardness value of the joint is uniform. The defective joint fractured in the weld nugget zone with the lowest tensile strength, while the fracture location of the defect-free joints changed to the heat affected zone. The impact energy of weld nugget zone is higher than that of the heat affected zone, and the impact energy of the two zones in defect-free joint both decreased with increasing rotation speed.     

厚板AZ31镁合金搅拌摩擦焊焊接接头的组织与性能

对10mm厚板A231镁合金成功进行了搅拌摩擦焊接,获得成形良好、表面光滑、无裂纹、无气孔的焊接接头.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,焊缝中心区是均匀细小的等轴晶粒,热力影响区晶粒大小不均匀,存在较明显的塑性流变带结构;焊接接头的抗拉强度达到母材的80%以上,焊接接头的冲击韧性比母材高,焊接接头的显微硬度比母材稍有降低,焊接接头具有较好的力学性能,说明搅拌摩擦焊是焊接厚板镁合金的一种有效方法.