搅拌摩擦加工技术研究进展

搅拌摩擦加工是一种新型固相加工技术.本文主要介绍了搅拌摩擦加工技术的基本原理及其在材料微观结构改性、制备细晶超塑性材料和金属基复合材料方面的研究进展,并展望了其发展前景.     

摩擦搅拌表面改性技术研究进展

摩擦搅拌表面改性技术通过对材料表层进行摩擦加热和机械搅拌,产生强烈塑性变形和动态再结晶,可以显著细化表层组织,消除铸造缺陷.通过直接添加或原位固相反应可以形成颗粒增强复合表层,使材料表面硬度和耐磨性以及整体机械性能得到显著改善.摩擦搅拌表面改性固相加工的特点还使其具有良好的工艺性能.作为一项清洁高效的先进表面工程技术,摩擦搅拌表面改性技术具有广阔的应用前景.     

摩擦搅拌焊接和摩擦搅拌加工技术的应用现状

综合评述了摩擦搅拌焊接技术(FSW)在航空航天器、船舶、陆路交通工具等制造领域的应用现状。摩擦搅拌加工技术(FSP)是近些年发展起来的一种金属材料新型加工处理技术,简介了该技术的基本原理,以及在晶粒细化、制备超塑性材料与表面复合材料中的应用。展望了摩擦搅拌焊接及摩擦搅拌加工技术的应用前景。     

镁合金表面搅拌摩擦原位复合材料化的新方法

为了解决搅拌摩擦加工在进行复合材料制备过程中增强相需预置,及在基体中分布不均的问题,提出表面搅拌摩擦原位复合材料化的新方法.利用搅拌头在轧制态AZ31镁合金板材上进行表面复合材料制备,并对制备的复合材料进行显微观察、微观硬度测试、表面耐磨度测试.结果表明,相较于预置搅拌摩擦加工制备复合材料的方法,文中方法能够使增强相在基体中分布更加弥散、均匀,从而进一步提高复合材料层的显微硬度,以及材料表面的耐磨度,同时简化了搅拌摩擦加工制备复合材料的工艺过程.     

基于摩擦加工技术的镁合金表面改性研究现状

鉴于当前高性能镁合金的应用需求,亟待提高镁合金的表面硬度、摩擦磨损性以及耐蚀性等表面性能。新型固态加工技术——搅拌摩擦加工以及摩擦堆焊能够实现材料的大塑性变形,在镁合金表面微观组织结构改性、表面复合材料化以及金属焊敷层制备等方面得到了成功的应用。在介绍搅拌摩擦加工以及摩擦堆焊技术特性的基础上,分别从工艺手段、组织演变以及性能改善等方面综述了摩擦加工技术用于镁合金表面改性的研究现状。国内外研究结果显示,搅拌摩擦加工可有效细化镁合金表面晶粒,破碎粗大第二相,导入增强粒子,实现表面复合化,进而显著提高镁合金的硬度、耐磨性以及耐蚀性。摩擦堆焊技术可在镁合金表面成功制备无稀释、结合完整性高、均匀细化的金属焊敷层,有效改善镁合金表面硬度及耐磨性。通过对用于镁合金表面改性的摩擦加工技术研究现状的总结,展望了镁合金搅拌摩擦加工以及摩擦堆焊的发展前景,提出了需要进一步研究的方向。     

第二相粒径和振动对FSP制备AZ91/SiC表面复合层的影响（英文）

采用改进的搅拌摩擦加工方法 (FSP)加工AZ91镁合金试样。这种新方法称为"振动搅拌摩擦加工方法(FSVP)"。Si C纳米颗粒作为第二相粒子,利用FSP和FSVP制备合金的表面复合层,研究不同粒径(30nm和300nm)的Si C强化颗粒对复合材料表面不同性能的影响。结果表明,采用FSVP工艺能细化材料的显微组织,提高材料的硬度、延展性和强度等力学性能。粒径为30 nm的增强颗粒对复合材料显微组织和力学性能的影响大于粒径为300nm的增强颗粒。振动频率越高,FSV试样的力学性能和显微组织越好;当FSV振动频率为50和25 Hz时,搅拌区硬度值分别约为157和116 MPa。     

搅拌摩擦加工制备镁合金表面复合层的显微组织和力学性能

选用轧态AZ31镁合金为基体、C60颗粒为增强相,采用搅拌摩擦加工技术(FSP)制备镁合金表面复合材料,搅拌针头旋转速度为600 r·min~(-1),加工速度为118 mm·min~(-1),分别进行1～3道次FSP加工后,通过金相、透射、硬度和拉伸等测试,对搅拌加工区复合显微组织和力学性能进行表征分析。研究表明:FSP可使镁合金晶粒显著细化; C60加入后,在1～3道次FSP内,随着加工道次升高,C60分散程度上升,复合材料平均晶粒尺寸降低,材料硬度上升,抗拉强度上升,但弥散于晶间的团聚颗粒使其拉伸性能低于母材;添加C60后的试样中,2道次硬度有明显上升,最高硬度可达母材的1. 73倍,3道次试样硬度平均值最高。结果表明,可通过FSP制备镁基表面复合层强化材料。     

碳纳米管表面强化高强铝合金磨损性能研究

用搅拌摩擦加工(FSP)技术将多壁碳纳米管(MWCNTs)添加在LC9铝合金板表面,并在其表层形成碳纳米管铝基复合材料,表面强化高强铝合金材料.结果表明,MWCNTs的加入,可使铝基复合材料的耐磨性明显提高.随着MWCNTs含量的增加,复合材料的磨损量呈降低趋势,耐磨性能提高.在复合材料表面主要发生了磨粒磨损现象.     

Al3Ti-SiCp/Al-13Si复合材料力学性能研究

分析了利用原位反应和液态搅拌合成技术制备的Al3Ti-SiCp／Al-13Si复合材料的微观组织和增强相的微观结构，检测了该复合材料的力学性能，探讨了该复合材料的增强机理。研究结果表明：(1)T6态下该复合材料的室温、高温力学性能相对于基体材料分别提高了8％和20％，弹性模量提高了17％；(2)增强相主要是Al3Ti-SiCp；(3)增强机理是：细晶强化、颗粒增强和固溶时效强化。     

搅拌铸造法制备金属基复合材料的热力学和动力学机制

对搅拌铸造制备金属基复合材料中增强相粒子进入金属溶液的热力学和动力学机制进行了推导，得出了粒子进入金属溶液中外力做功与润湿角、粒子密度、熔体密度、粒径和表面张力的关系式，为采用搅拌铸造法制备金属基复合材料时制订工艺参数提供了理论依据。     

Friction stir processing of aluminum cast alloys for high performance applications

Friction stir processing (FSP) is a novel process developed based on the principle of friction stir welding (FSW) that locally manipulates the microstructure by imparting a high level of energy in the solid state resulting in improved mechanical properties. Additionally, FSP has emerged as an advanced tool to produce surface composites by embedding second phase particles into the matrix. Our work to date has shown that FSP can be implemented as a post-casting method to locally eliminate casting defects, such as porosity due to gas evolution during casting. Coarse second phases are broken up into fine nearly equiaxed particles and distributed uniformly in the matrix; grain refinement is also attained by dynamic recrystallization during FSP. This results in improved mechanical properties. Furthermore, our work shows that friction stir processing is a viable means of producing localized composite zones in cast Al components. Such improvements have important implications for manufactured components for diesel engines and for critical and high integrity components. The convenience of FSP as a post-processing step that can easily be carried out during machining operation makes it quite attractive for adoption.     

Friction Stir Processing of Magnesium Alloys:A Review

Magnesium(Mg) alloys have been extensively used in various fields, such as aerospace, automobile, electronics, and biomedical industries, due to their high specific strength and stiff ness, excellent vibration absorption, electromagnetic shielding eff ect, good machinability, and recyclability. Friction stir processing(FSP) is a severe plastic deformation technique, based on the principle of friction stir welding. In addition to introducing the basic principle and advantages of FSP, this paper reviews the studies of FSP in the modification of the cast structure, superplastic deformation behavior, preparation of finegrained Mg alloys and Mg-based surface composites, and additive manufacturing. FSP not only refines, homogenizes, and densifies the microstructure, but also eliminates the cast microstructure defects, breaks up the brittle and network-like phases, and prepares fine-grained, ultrafine-, and nano-grained Mg alloys. Indeed, FSP significantly improves the comprehensive mechanical properties of the alloys and achieves low-temperature and/or high strain rate superplasticity. Furthermore, FSP can produce particle-and fiber-reinforced Mg-based surface composites. As a promising additive manufacturing technique of light metals, FSP enables the additive manufacturing of Mg alloys. Finally, we prospect the future research direction and application with friction stir processed Mg alloys.     

搅拌摩擦加工铸态铝铁合金的显微组织

采用普通熔铸法制备含铁3%(质量分数)的铝铁二元合金,研究多道次往复搅拌摩擦加工(Friction stir processing,FSP)对合金显微组织的影响。结果表明:进行1~3道次往复FSP后,各道次加工区组织不均匀;随着加工道次的增加,组织均匀细化程度增大。合金铸态组织由α-Al和粗大针状Al3Fe相组成,经3道次FSP后,搅拌区组织明显细化。原始铸态组织转变为细小等轴的再结晶晶粒,尺寸为2~5μm,并且部分晶粒中出现层错;粗大的Al3Fe针状相被破碎成长度小于1μm的细小粒状,弥散分布在铝基体晶界和晶粒内部,细化的Al3Fe粒子呈现孪晶结构。     

Laser-assisted friction stir processing of IN738LC nickel-based superalloy: stir zone characteristics

Friction stir processing (FSP) of high softening-temperature materials such as nickel-based superalloys is considered to be difficult. Laser heating of a localised area ahead of the FSP tool was used to provide sufficient plasticity during the FSP of IN738LC nickel-based superalloy. The stir zone (SZ) microstructure of the friction stir processed and laser-assisted friction stir processed were characterised. Laser-assisted friction stir processing (LAFSP) produced a defect-free pass, but FSP resulted in generation of a discontinuity in the SZ. Both lower volume fraction of partially dissolved γ′ precipitates and coarser grain structure of SZ in LAFSP led to more ductility of the SZ material and elimination of the defects.     

Effect of second-phase particle size and presence of vibration on AZ91/SiC surface composite layer produced by FSP

An improved method of friction stir processing (FSP) was introduced for the processing of AZ91 magnesium alloy specimens. This novel process was called “friction stir vibration processing (FSVP)”. FSP and FSVP were utilized to develop surface composites on the studied alloy while SiC nanoparticles were applied as second-phase particles. The effect of reinforcing SiC particles with different sizes (30 and 300 nm) on different characteristics of the composite surface was studied. The results indicated that the microstructure was refined and mechanical properties such as hardness, ductility, and strength were enhanced as FSVP was applied. Furthermore, it was concluded that the effect of reinforcing particles with a size of 30 nm on the microstructure and mechanical properties of the surface composite was more obvious than that of particles with a size of 300 nm. It was also found that mechanical properties and microstructure of FSV-processed specimens were improved as vibration frequency increased. The hardness value in the stir zone was about 157 MPa for the FSV-processed specimen at a vibration frequency of 50 Hz, while this value was around 116 MPa for the FSV-processed specimen at a vibration frequency of 25 Hz.     

搅拌摩擦在超塑性材料焊接及成形方面的应用

大量的研究结果表明搅拌摩擦焊接是保证超塑性材料焊接后仍能保持高强度和高塑性的有效焊接方法。尤其是在高应变速度、低温和较低流动应力情况，采用搅拌摩擦成形（Friction Stir Process:FSP）技术来生产超塑性材料是相对简单且有效的方法。对搅拌摩擦在超塑性材料焊接和成形方面的进展做了简要的总结，包括材料、工艺参数及其影响因素等方面。     

等离子旋转电极法制备钛铝粉末性能表征

采用等离子束旋转电极法制备Ti-47Al-2Cr-2Nb球形粉末,粉末的平均粒径d50为85 μm, 松装密度为2.65 g/cm3。截线法测得粉末的球形度为99.6%;粉末的流动性为10.40 s/50 g;粉末的平均氧、氮含量分别为0.05%和0.004%。XRD分析表明,粉末的相组成为α2相和γ相,主相为富钛α2相;粉末经热等静压后主相为γ相,伴随少量α2相。SEM背散射照片表明,粉末颗粒的晶粒为胞状组织,晶粒平均大小约为2 μm;对不同粒径的颗粒进行EPMA分析表明,颗粒内部化学成分与预合金棒接近,颗粒表面有部分Al元素挥发,约为2at%     

搅拌摩擦加工研究进展及前景展望

对搅拌摩擦加工工艺、加工对性能的影响及其在制备复合材料及合金等方面的研究做了比较详尽的综述,并指出搅拌摩擦加工研究进程中存在的问题、发展前景及今后的研究方向。认为对非正常晶粒长大的影响因素及其产生机制还有待深入研究。熔化焊结合搅拌摩擦加工能满足钛合金等高强材料焊接的需要。用搅拌摩擦加工制备纳米相增强金属基复合材料和金属间化合物将有良好的应用前景。为解决材料微观结构不均匀现象,基于搅拌摩擦加工基本思想,开发新的适合材料制备的新工艺将是该技术从实验室成功走向实际应用的瓶颈