挤压变形对MB15镁合金及组织性能的影响

对MB15镁合金进行热处理,然后进行挤压试验,挤压变形MB15镁合金组织以剪切条纹和细小的α再结晶等轴晶为基本特征.挤压变形可显著地细化镁合金晶粒并提高镁合金的力学性能.随挤压比的增大,晶粒细化程度增加;强度、硬度随挤压比的增大而增大.所制定的工艺合理,挤压出的管材、型材有较好的力学性能.     

AZ31镁合金薄壁管材挤压技术研究

目的得到综合力学性能良好的AZ31镁合金Φ8 mm薄壁管材。方法研究了热挤压、等温挤压与反向温度场挤压3种工艺对AZ31镁合金薄壁管材晶粒组织和力学性能的影响。结果热挤压管材组织不均匀,头部晶粒粗大、尾部细小,等温挤压和反向温度场管材挤压组织较为均匀。结论反向温度场挤压在模具温度为300℃、坯料温度为20℃条件下,薄壁管材抗拉强度达278MPa,伸长率达20.1%,综合力学性能最佳。     

连续挤压制备铝包镁复合棒材的组织与力学性能EI北大核心

在不同的加热温度下,采用不同尺寸的坯料并利用连续挤压工艺进行6063铝合金包AZ31镁合金复合材料的制备,获得尺寸为∅5 mm的复合棒材。通过扫描电镜(SEM)、金相显微镜以及万能拉伸试验机等分析手段对制备的复合棒材进行微观组织分析和力学性能测试。结果表明:连续挤压工艺可显著细化复合棒材镁芯的晶粒。坯料在室温挤压时,镁芯的平均晶粒尺寸为15.4μm,复合棒材的抗拉强度为141.4 MPa,伸长率为6.6%。加热温度升高至450℃时,镁芯晶粒开始长大,复合棒材的抗拉强度略有下降,伸长率提高到10%。随着镁芯直径增大,组织均匀性和晶粒细化效果提高,平均晶粒尺寸为12.8μm。在连续挤压过程中,铝镁之间发生相互扩散,产生硬度较高的铝镁结合层,结合层最大厚度为4.8μm。利用Deform有限元软件模拟连续挤压过程中的材料流动,得到了Al和Mg的温度与应变分布,有助于分析连续挤压过程中复合棒材的组织演变。     

连续挤压制备铝包镁复合棒材的组织与力学性能

在不同的加热温度下,采用不同尺寸的坯料并利用连续挤压工艺进行6063铝合金包AZ31镁合金复合材料的制备,获得尺寸为?5 mm的复合棒材。通过扫描电镜(SEM)、金相显微镜以及万能拉伸试验机等分析手段对制备的复合棒材进行微观组织分析和力学性能测试。结果表明：连续挤压工艺可显著细化复合棒材镁芯的晶粒。坯料在室温挤压时,镁芯的平均晶粒尺寸为15.4μm,复合棒材的抗拉强度为141.4 MPa,伸长率为6.6%。加热温度升高至450℃时,镁芯晶粒开始长大,复合棒材的抗拉强度略有下降,伸长率提高到10%。随着镁芯直径增大,组织均匀性和晶粒细化效果提高,平均晶粒尺寸为12.8μm。在连续挤压过程中,铝镁之间发生相互扩散,产生硬度较高的铝镁结合层,结合层最大厚度为4.8μm。利用Deform有限元软件模拟连续挤压过程中的材料流动,得到了Al和Mg的温度与应变分布,有助于分析连续挤压过程中复合棒材的组织演变。     

管材挤压工艺分析及实验研究

对管材挤压成形进行了工艺分析及实验研究.确定了镁合金、7075铝合金、高温合金等几种材料管材挤压成形工艺参数,分析了管材挤压成形时变形力的变化规律.研究结果表明,管材挤压成形时必须严格控制坯料温度、模具预热温度、润滑方式、挤压速度、挤压比等工艺技术参数.以上工艺参数对挤压力均有不同程度的影响.     

基于数值模拟和实验的Mg/Al复合管材成形工艺研究

目的 为了实现Mg/Al双金属管材的良好成形,提出了一种新方法,即将直接挤压和扩径剪切变形工艺相结合来制备具有良好性能的Mg/Al双金属管材,并探究挤压温度对Mg/Al复合管材成形过程的影响。方法 采用DEFORM–3D有限元软件对Mg/Al双金属管材成形过程进行模拟,以定量分析不同挤压温度对生产的复合管材的影响,并结合模拟结果了解共挤过程中铝和镁合金之间发生的材料流动和冶金反应特点。对挤出管材进行微观组织和力学实验表征。结果 仿真结果表明,由于材料特性的差异,挤压温度对挤压双金属结合性能的影响体现在多个方面,如挤压过程中原子扩散能、流动应力差异等。硬度测试结果表明,合理控制挤压温度可以在减小结合层厚度的同时提升基体材料的硬度。结论 由直接挤压–扩径剪切变形(DEES)工艺制备的Mg/Al双金属复合管材结合良好,结合界面无缺陷和裂纹。结合层厚度在390 ℃时最低,在420 ℃时最高,当挤压温度为390 ℃时,基材的硬度最高,应该合理控制挤压温度以获得更优性能的复合管材。DESS工艺可以有效细化晶粒,最终形成均匀细小的等轴晶。     

SiCp/AZ91复合材料大口径管材的热挤压成形研究

目的 解决镁基复合材料大口径管材成形加工困难的问题。方法 通过搅拌铸造技术制备的SiC颗粒增强AZ91镁基复合材料百公斤级铸锭坯料,开展了大口径镁基复合材料管材的热挤压成形工艺优化,分析复合材料变形过程中组织与力学性能演变规律,并揭示了其微观机制。结果 复合材料管材最佳热挤压工艺参数为：挤压温度为400 ℃,挤压速度为1 mm/s,在最佳的工艺下成功成形出外径260 mm和130 mm的SiC颗粒增强AZ91镁基复合材料挤压管材,复合材料挤压管材的弹性模量、屈服强度、抗拉强度、伸长率分别可以达到72 GPa,302 MPa,356 MPa,1.2%。结论 对温度、挤压比、挤压速度等工艺参数的优化,以及利用SiC颗粒对再结晶行为的促进作用,是制备出大尺寸复合材料管材的关键。     

温成形杯形件组织性能研究

为研究杯形件温成形后的组织性能,对某杯形件进行了温挤压-引伸实验,并对所得杯形件毛坯和原材料的金属流线、晶粒度、硬度和拉伸性能进行了测定和分析.结果表明:温成形可使杯形件晶粒细化和均匀化;采用温挤压-引伸工艺成形的杯形件毛坯金属流线完整,硬度和抗拉强度比原材料有大幅度提高,塑性略有降低;采用同样热处理工艺对温成形杯形件与原材料进行处理,杯形件的抗拉强度和塑性都比原材料略有提高.     

坯料温度对AZ31镁合金反挤成形的影响

在300～400℃温度范围内,挤压比λ=5的条件下,对铸造态AZ31镁合金的反挤压成形进行了实验研究,分析了挤压变形力、挤压成形性以及组织性能的变化规律.实验结果表明:AZ31镁合金在300～400℃范围内反挤成形,随变形温度的升高,挤压变形力呈现下降的趋势;而△T(坯料温度的不均匀度)的增大,使得挤压件表面质量变差,外表面出现垂直于挤压方向的横向裂纹;随变形温度的降低,挤压件晶粒逐步细化,硬度上升.为AZ31镁合金反挤压变形温度的优化提供了基础.     

连续流变挤压技术在制备高性能铝材中的应用

目的探索铝材短流程制备工艺,制备出高性能铝合金材料。方法采用连续流变挤压成形技术制备Al-Ti-B晶粒细化剂与Al-Sc-Zr耐热铝合金导线;利用提出的连续流变挤压与累积连续挤压法,制备超细晶金属材料。结果采用连续流变挤压成形技术制备Al-Ti-B晶粒细化剂,其细化效果优于国外同类产品,且制备流程短、成本低;制备出的高性能的Al-Sc-Zr耐热铝合金导线,其抗拉强度、伸长率和导电率分别达到223 MPa、7.1%和60.5%IACS,并且可在230℃的温度下长期运行,相比于日本耐热铝合金导线,其抗拉强度、伸长率与导电率分别提高了39.4%,255%,0.83%;采用连续挤压技术制备的Al-Sc-Zr合金杆,经过累积连续挤压后,合金晶粒尺寸从100μm细化至800 nm,得到了超细晶Al-Sc-Zr合金。结论连续流变挤压技术制备铝材工艺流程短、产品性能优良,能连续高效制备铝合金超细晶材。     

Fabrication,microstructures, and tensile properties of magnesium alloy AZ91/SiCp composites produced by powder metallurgy

Abstract

The tensile properties and microstructural evolution of hot extruded AZ91 magnesium alloy with and without reinforcement of SiC particles have been investigated in terms of extrusion parameters, such as extrusion ratio and extrusion temperature. Also, the effect of SiC particles on the grain size of the matrix in the composites was evaluated using the Hall-Petch equation. The AZ91 magnesium alloy powders prepared by wet attrition milling from magnesium machined chips were hot pressed with and without SiC particles, hot extruded, and then solution treated. Microstructural observation revealed that both the composites and the magnesium alloy have fine equiaxed grains due to the dynamic recrystallisation during hot extrusion. The tensile strength of both materials increased with increasing extrusion ratio, and the strengths of the composites were higher than that of the magnesium alloy without reinforcement. It was found that the tensile strength of both the materials decreased after solution treatment, and the decrease in tensile strength of the composites was considerably smaller than that of the magnesium alloy. From analyses of the microstructures and the mechanical properties, combined with examination of the H all–Petch relationship, the refinement of the matrix was primarily responsible for the improvement in the yield strength of the composites. The grain growth of the matrix was inhibited by the introduction of the SiC particles.     

Application of superplasticity in commercial magnesium alloy for fabrication of structural components

Abstract

An investigation of the superplastic characteristics of magnesium alloys with several grain sizes revealed that grain boundary sliding took place more easily with grain refinement. The required grain size for high strain rate superplastic forming was estimated to be ～2 µm. The required grain structure could be obtained by several procedures, hot extrusion with a high extrusion ratio, severe plastic deformation via equal channel angular extrusion, consolidation of machined chip, and/or powder metallurgy processing of rapidly solidified powders, on a laboratory scale. The processing route of hot extrusion was selected in this study. An experimental study of superplastic press forming was conducted for a commercially extruded ZK60 alloy. The fabricated product did not essentially contain macroscopic defects, i.e. cracks or cavities. From an examination of tensile characteristics, it was found that the post-formed alloy exhibited higher strength and higher ductility compared with some conventional cast magnesium alloys, aluminium alloys, and steels. The experimental results support the possibility of using superplastically formed magnesium to produce structural components.     

Dynamic recrystallization behavior of AZ31 magnesium alloy processed by alternate forward extrusion

One of the important factors that affect the microstructure and properties of extruded products is recrystallization behavior. Alternate forward extrusion (AFE) is a new type of metal extrusion process with strong potential. In this paper, we carried out the AFE process experiments of as-cast AZ31 magnesium alloy and obtained extrusion bar whose microstructure and deformation mechanism were analyzed by means of optical microscopy, electron backscattered diffraction and transmission electron microscopy. The experimental results indicated that homogeneous fine-grained structure with mean grain size of 3.91 μm was obtained after AFE at 573 K. The dominant reason of grain refinement was considered the dynamic recrystallization (DRX) induced by strain localization and shear plastic deformation. In the 573-673 K range, the yield strength, tensile strength and elongation of the composite mechanical properties are reduced accordingly with the increase of the forming temperature. Shown as in relevant statistics, the proportion of the large-angle grain boundaries decreased significantly. The above results provide an important scientific basis of the scheme formulation and active control on microstructure and property for AZ31 magnesium alloy AFE process.     

动态流量控制法挤出镁合金三维弯曲管件

为了开发新的弯管件加工工艺,提出了一种动态调整传统分流挤压模具中分流孔内金属流量(dynamic flow control extrusion,DFCE)的挤压变形方法.在带有辅助调控挤压杆的630 T卧式挤压机上挤出镁合金弯管件,采用OM、SEM、TEM、拉伸试验等方法,研究了DFCE制造的镁合金弯管件的晶粒细化方式、微观组织结构和性能.结果表明:在变形温度450℃、直管挤压速度3 mm/s、弯管挤压速度1.5 mm/s、辅助调控挤压杆速度30 mm/s时,成功挤出变形均匀的弯管件;挤压后的直管部分和弯管部分的晶粒尺寸分别为7.9和12.8μm,且合金晶粒大小均匀;弯管部分室温拉伸强度和屈服强度分别由217和124 MPa提高到296和179 MPa,延伸率由12.9%提高到26.2%.DFCE挤压变形可以显著细化AZ91镁合金晶粒,其挤压过程中晶粒细化机制为位错驱动和动态再结晶,机械性能较铸态大幅度提高,坯料和挤出合金的拉伸断口分别呈现为准解理断裂和韧窝断裂的特征.     

AZ31镁合金薄板的无针搅拌摩擦加工

目的 研究有针、无针搅拌摩擦加工对AZ31镁合金薄板的微观组织和力学性能的影响.方法 通过搅拌摩擦加工技术(FSP)以不同的转速对AZ31镁合金薄板进行加工,采用拉伸试验机、金相显微镜、UMT摩擦磨损试验机、维氏硬度机对无针搅拌加工后的AZ31镁合金加工表面的晶粒形貌、拉伸性能、磨损性能和硬度进行研究分析,并与同转速有...     

固溶处理温度对GH3625合金热挤压管材微观组织和力学性能的影响

采用SEM、EDS和XRD等手段研究了不同固溶处理温度对GH3625合金热挤压管材组织性能的影响。结果表明,1 120℃是合金组织和力学性能的一个转折点。当固溶处理温度为910~1 120℃时,由于晶界处NbC相的钉扎作用,使得晶粒长大缓慢,合金硬度和强度缓慢下降;当固溶温度超过1 120℃时,NbC相大量回溶,钉扎作用减弱或消失,晶粒急剧长大,合金硬度和强度的下降趋势明显增大。随着固溶温度的升高,合金断口中的韧窝变得大而深邃,塑性逐渐提高;当固溶温度超过1 120℃时,拉伸断口基本以韧窝为主。GH3625合金热挤压管材在固溶处理时间为1h时的最佳固溶处理温度为1 120℃。     

循环道次对高温叠轧AZ31镁合金板材组织与性能的影响

目的通过高温累积叠轧工艺制备出高强度的镁合金,并研究该过程中循环道次对AZ31镁合金板材的微观组织与性能的具体影响。方法对累积叠轧1～5次板材进行微观组织观察,并进行显微硬度的测试,得到不同板材的硬度值,通过X射线衍射分析得到不同板材的取向结果,最终进行力学性能实验,并对比分析。结果随着循环道次的增加,板材抗拉强度有明显改变。从260 MPa先增加至310 MPa,最后稳定在350 MPa左右;非基面织构比重增加;断裂伸长率先降低后升高并稳定在10%左右。结论累积叠轧工艺使得AZ31镁合金板材产生了加工硬化,并显著细化了晶粒。循环道次的增加、孪晶产生和晶界数量显著增多导致强度进一步提高。     

挤压比对Al-0.68Mg-0.60Si合金组织和性能的影响

采用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱仪(EDS)、电子背散射衍射系统(EBSD)、透射电子显微镜(TEM)、硬度测试、室温拉伸测试等研究挤压比对Al-0.68Mg-0.60Si合金组织与性能的影响。结果表明:随着挤压比的增大,T6态Al-0.68Mg-0.60Si合金型材基体内的强化相弥散质点的尺寸逐渐减小,弥散程度增加,小角度晶界占比呈下降趋势,但再结晶分数有所提高,当挤压比达到39.6以上,合金内部基本为立方织构。此外,在挤压变形过程中,随着挤压比(λ=26.8~55.7)的增大,合金型材的硬度、抗拉强度先上升再下降;当λ=39.6时,合金的抗拉强度达到最大值284.00MPa。     

Mechanical behavior and wear characteristics of fine grained ZE41 magnesium alloy

ZE41 magnesium alloy was successfully produced by friction stir processing and grain refinement was achieved from a starting size of 107 μm±6.7 μm to 3.5 μm±1.5 μm. MgZn intermetallic which was appeared as network like structure at the grain boundaries before friction stir processing was greatly affected due to the severe plastic deformation and broken as small particles as observed from the microstructural studies. Higher hardness (≈30 %) was measured for the fine grained ZE41 magnesium alloy compared with the base alloy due to the grain refinement. From the tensile tests, yield strength and ultimate tensile strength was significantly increased at the cost of decreased ductility reflected in lower strain for the fine grained ZE41 compared with the base alloy. Wear studies showed higher coefficient of friction and lower mass loss for the grain refined ZE41 magnesium alloy. From the results, it can be understood that the grain refinement achieved by friction stir processing has a profound influence on enhancing the mechanical and tribological properties of ZE41 magnesium alloy.     

难变形材料热静液挤压复合精密塑性成形工艺

目的 研究热静液挤压及其复合塑性变形工艺在高密度钨合金、钨铜合金、钛基复合材料及镁合金薄壁细管等难变形材料方面的制备。方法 通过对高密度钨合金难变形材料进行热静液挤压及旋转锻造等塑性成形,分析了材料在成形过程中的微观组织及性能变化规律和强化机制,制备出大长径比穿甲弹弹芯材料。在此基础上,将该复合塑性变形技术拓展至两相不互溶材料钨铜合金、钛基复合材料及大长径比镁合金毛细管等难变形材料方面的制备。结果 热静液挤压及其复合塑性变形工艺在粉末冶金难变形材料的致密化方面具有显著优势,获得材料不仅致密度高,而且有效实现了控形控性;对于镁合金薄壁细管成形而言,也可以实现组织与性能的有效调配,同时材料的精度较高。结论 热静液挤压及其复合塑性变形工艺在难变形材料的制备与成形方面具有独特的优势与广阔的应用前景。