6061铝合金复合挤压有限元模拟及试验研究

利用Deform三维有限元软件模拟了室温6061铝合金两种路径复合挤压(cyclic equal channel compression,CECC)的变形过程。结果表明:试样经反复镦挤(cyclic channel die compression,CCDC)+等通道转角挤压(equal channel angular pressing,ECAP)复合挤压路径的等效应力与等效应变较大,晶粒细化效果比ECAP+CCDC路径好。CCDC+ECAP路径试样的抗拉强度较高,其断口表现出韧性断裂的特征。CCDC+ECAP是最佳的复合挤压路径之一。     

工业纯铝等通道球形转角膨胀挤压变形的力学与摩擦学性能（英文）

对传统等通道转角挤压工艺(equal channel angular extrusion, ECAE)进行改进,提出一种新型剧烈塑性变形法(severe plastic deformation, SPD)——等通道球形转角膨胀挤压(equal channel angular expansion extrusion with spherical cavity, ECAEE-SC)。该工艺通过耦合镦-剪-挤等多种变形效应,可在单道次挤压下实现坯料内部较大的塑性应变累积,进而获得理想的晶粒细化与性能提升效果。在室温条件下采用ECAEE-SC工艺对工业纯铝(Al-1060)进行单道次挤压,并与相同条件下的2道次ECAE处理变形结果进行对比。采用EBSD、SEM等测试手段,研究了工业纯铝经ECAEE-SC变形晶粒特征与磨损表面形貌,并测试了变形材料显微硬度、拉伸性能与摩擦学性能。结果表明,在ECAEE-SC工艺剧烈塑性应变诱导下,工业纯铝经单道次挤压变形后晶粒显著细化,呈典型的剪切条带状特征。与初始退火态相比,变形材料显微硬度与抗拉伸强度分别提升了92.6%和91.8%,且性能提升效果明显优于2道次ECAE变形。同时,ECAEE-SC工艺有效提高了工业纯铝的耐磨性能,工业纯铝变形后表面磨痕宽度最小,磨痕深度最浅,其磨损机理以磨粒磨损为主导。     

ECHE挤压对AZ31镁合金组织和性能的影响

提出了等通道螺旋转角挤压(equal channel helix angular extrusion,ECHE)变形方法,采用Deform-3D平台的有限元模拟、OM、SEM、TEM、拉伸试验等方法,研究了ECHE制造AZ31镁合金轻质螺栓坯料的挤压工艺、温度场、合金流动情况、组织和性能。结果表明:在变形温度为380℃,挤压速度为3mm·s-1时,合金变形均匀,不易出现挤压缺陷;等通道螺旋转角挤压变形可以显著细化AZ31镁合金晶粒;其挤压过程中晶粒细化机制为晶粒破碎和动态再结晶;挤压后的平均晶粒尺寸为3～5μm,且合金晶粒大小均匀;力学性能较铸态大幅度提高,室温抗拉强度和屈服强度分别由209和104MPa提高到286和165MPa,延伸率由11%提高到26.4%,拉伸断口呈现为韧窝断裂和准解理断裂的混合特征。     

等通道转角挤压制备超细晶材料的最新研究进展

等通道转角挤压(Equal channel angular pressing,ECAP)方法是制备性能优异超细晶材料最常见的大塑性变形方法之一。模角、挤压路径、挤压道次、挤压温度和挤压速度等因素都会影响等通道转角挤压制备超细晶材料的性能;等通道转角挤压的模具也在不断地优化,如背压-等通道转角挤压(Back pressure ECAP,BP-ECAP)模具、可加热的模具以及在等通道转角挤压基础上形成的板材连续剪切技术等,这些新的模具可以改变ECAP变形过程中的组织均匀性。本文综述了等通道转角挤压制备超细晶材料的最新研究进展,并指出了几个需要深入研究的问题及方向。     

等通道球形转角膨胀挤压工业纯铝的组织与性能

采用新型等通道球形转角膨胀挤压(equal channel angular expansion extrusion with spherical cavity,ECAEE-SC)工艺,对工业纯铝进行室温1道次挤压变形。借助光学显微镜(OM)、电子背散射衍射(EBSD)研究变形过程中工业纯铝显微组织的变化规律,并进行了硬度测试和拉伸试验。结果表明:ECAEE-SC工艺具有复合成形效果和较高的挤压效率,坯料成功实现了单道次连续变形。工业纯铝经1道次ECAEE-SC变形后,在机械剪切、应变累积和静水压力的共同作用下,晶粒显著破碎和细化,内部形成了大量细小、均匀的等轴亚晶,平均晶粒尺寸约为4.6mm;材料表现出优良的综合力学性能,HV显微硬度由未变形时的366 MPa增加至702 MPa,增幅为91.8%,且分布趋于均匀;抗拉强度高达183.8 MPa,而伸长率降低至12.7%,拉伸断口表现出明显的韧性断裂特征。     

剧烈塑性变形对AZ31镁合金微观组织演化的影响

等截面通道角挤压(equal channel angular extrusion,ECAE)是制备无疏松孔洞大块超细晶材料的重要方法之一。通过刚塑性有限元法对ECAE进行三维数值仿真,采用单元点映射方法,结合三维模型转换进行了A,Ba,Bc和C多次挤压路线的有限元连续仿真,得出了圆形截面挤压试样等效应变分布及其变形均匀性规律,同时,给出了多次挤压不同挤压路线等截面通道角挤压晶粒细化机理。通过变换挤压路线可以改变挤压试样内部微观组织结构。随着挤压次数的增加,不同挤压路线对应挤压试样均得到有效细化,与其它挤压路线相比,路线Bc和C能够得到大角度晶界的等轴晶粒分布的挤压试样。同时,通过实验得到的各路线挤压试样对应的微观结构演化规律与模拟分析得到的应变分布规律一致。     

基于FEM的战地车用AZ31镁合金板材ICAE工艺研究

细化晶粒、提高金属综合性能是当前战地车用AZ31镁合金板材塑性成形工艺迫切需要研究的内容。提出了AZ31镁合金板材的减径通道转角(Ironing channel angular extrusion,ICAE)挤压成形工艺。采用数值模拟结合理论分析的方法,对ICAE工艺下200 mm×2 mm的AZ31镁合金板材微观组织演化规律进行了研究。结果表明:ICAE通过晶粒破碎和动态再结晶可以显著细化AZ31镁合金晶粒,板材平均晶粒尺寸可达15μm。     

复合镦挤法制备超细晶1060铝合金的有限元模拟

采用一种新的复合镦挤法(Cyclic equal channel compression,CECC)制备了超细晶1060铝合金,即等通道转角挤压(Equal channel angular pressing,ECAP)与多向压缩(Multi-axial compression,MAC)的组合工艺,并通过电子背散射衍射技术(EBSD)分析了复合镦挤后试样的微观组织。为了验证实验的可行性,利用DEFORM 3D软件对试样复合镦挤过程中的损伤值、最大主应力、等效应力、等效应变的变化过程进行了模拟。结果表明:模拟结果显示各项参数变化均在正常范围内;复合镦挤之后,试样的晶粒组织均匀细小且接近于等轴状,得到了优异的超细晶组织。     

ECAP对T2工业纯铜的性能影响及实验过程模拟

在室温下运用等通道转角挤压技术(equal channel angular pressing,ECAP)对T2工业纯铜进行了多道次的挤压,并对各道次材料进行了不同温度的退火处理.研究了材料存经历不同挤压道次和不同退火温度后强度和韧性的变化规律.并运用ABAQUS软件对实验过程中材料的受力情况进行了模拟.结果表明,T2工业纯铜在BC路径下经历多次挤压后,晶粒得到细化.将材料在433、453和473 K下进行1 h的退火处理后,材料的强度有所增强,材料的韧性变化不大.     

等通道球形转角挤压过程中工业纯铝的微观组织演变与力学性能

突破传统ECAP变形全过程通道等截面思路,提出一种耦合剪切应变和正应变于一体的新型等通道球形转角挤压(equal channel angular extrusion with spherical cavity,ECAE-SC)工艺。在自行研制的模具上对工业纯铝进行室温单道次ECAE-SC挤压实验,采用OM、EBSD和TEM等技术手段,研究了ECAE-SC变形过程中工业纯铝微观组织的演变规律,并测试了变形后试样的显微硬度。结果表明,在ECAE-SC工艺剧烈简单剪切变形诱导下,工业纯铝仅需1道次挤压变形即可获得等轴、细小、均匀的超细晶组织,平均晶粒尺寸约为400 nm;工业纯铝室温ECAE-SC变形以位错滑移为主并伴有不完全连续动态再结晶,其微观组织经历了剪切带→位错胞→小角度亚晶→大角度等轴晶粒等动态演化过程。1道次ECAE-SC变形后,工业纯铝组织以{110}001高斯织构为主,同时存在部分{111}112铜型织构;材料显微硬度值大幅提升,由初始289.4 MPa提高到565.3 MPa,增幅高达95.33%,且分布均匀性良好。     

Super-Elasticity Characteristics of TiNi Alloy Processed by Equal Channel Angular Extrusion

A Ni-rich TiNi alloy was processed by Equal Channel Angular Extrusion (ECAE) at 500℃. After four passes ECAE treatment, microstructure of the alloy was refined but slightly inhomogeneous, to sub-micron scale, approximately 0.5～0.6 μm. Comparing with the solution-treated TiNi specimen, the martensitic transformations start (Ms) and peak temperatures (Mp) of TiNi specimens processed by ECAE were dramatically lowered. After ECAE treatment, the R-phase transformation was stimulated and separated from martensiti...     

Severe plastic deformation of commercially pure aluminum using novel equal channel angular expansion extrusion with spherical cavity

Equal channel angular expansion extrusion with spherical cavity (ECAEE-SC) was introduced as a novel severe plastic deformation (SPD) technique, which is capable of imposing large plastic strain and intrinsic back-pressure on the processed billet. The plastic deformation behaviors of commercially pure aluminum during ECAEE-SC process were investigated using finite element analysis DEFORM-3D simulation software. The material flow, the load history, the distribution of effective strain and mean stress in the billet were analyzed in comparison with conventional equal channel angular extrusion (ECAE) process. In addition, single-pass ECAEE-SC was experimentally conducted on commercially pure aluminum at room temperature for validation, and the evolution of microstructure and microhardness of as-processed material was discussed. It was shown that during the process, the material is in the ideal hydrostatic stress state and the load requirement for ECAEE-SC is much more than that for ECAE. After a single-pass ECAEE-SC, an average strain of 3.51 was accumulated in the billet with homogeneous distribution. Moreover, the microstructure was significantly refined and composed of equiaxed ultrafine grains with sub-micron size. Considerable improvement in the average microhardness of aluminum was also found, which was homogenized and increased from HV 36.61 to HV 70.20, denoting 91.75% improvement compared with that of the as-cast billet.     

纯铝等径角挤扭新工艺变形

等径角挤扭(ECAPT)是结合等径角挤压(ECAP)和挤扭(TE)两种典型的大塑性变形(SPD)工艺而产生的一种新型细晶材料制备技术。利用刚塑性有限元技术对纯铝1100ECAPT工艺变形特征进行模拟研究,获得了等效应变和等效应力的大小及分布规律,分析了挤压载荷随变形时间的变化规律及其对试样变形的影响。结果显示,在模具拐角和螺旋通道处,等效应变得到有效积累,最终呈层状分布,且相对较为均匀,应变分布均匀性也得到一定改善,等效应力在上述两处区域达到最大。采用纯铝进行室温3道次ECAPT实验,测量试样显微组织和力学性能的变化。结果表明,实验结果与模拟结果具有较好的一致性;晶粒得到了明显细化,屈服强度、抗拉强度与显微硬度等力学性能得到明显提高,但试样塑性略有降低。     

等通道转角挤压对L2工业纯铝力学性能的影响

利用等通道转角挤压(ECAP)技术挤压工业纯铝L2，探讨了挤压次数对其力学性能的影响。结果表明，随挤压次数的增加，L2的抗拉强度和硬度得到显著提高，抗拉强度可提高95％，硬度提高70％。挤压1次后，其伸长率由40％下降至15％，此后伸长率基本保持稳定。     

等径角挤扭工艺的研究

针对等径角挤压（ECAP）工艺和挤扭（TE）工艺中,材料变形不均匀,1道次变形获得的应变量不够大的缺点,将2种工艺有机结合,提出了等径角挤扭（ECAPT）工艺。利用UG和DEFORM-3D软件进行几何造型和有限元模拟,研究变形过程、应力应变分布和载荷变化,并用纯铝进行2道次ECAPT实验,测量试样显微组织和力学性能的变化。结果表明,ECAPT使组织产生更大的应变量,随着行程的增加,载荷增大,在TE通道平稳阶段达最大值,试样头部挤出TE通道后载荷降低;材料的宏观形貌同模拟结果一致,显微组织发生了明显细化,其中第1道次z面和第2道次y面细化效果明显;力学性能得以较大提高,屈服强度由43．31MPa提升至52．19MPa,抗拉强度由71．30MPa提升至130．38MPa。     

模具外角对等通道转角挤压纯铝变形过程的影响

模具外角对等通道转角挤压(ECAE)变形过程影响较大,文章利用有限元软件(MSC.Marc)模拟研究了模具外角对ECAE过程中等效应变、变形机理的影响。模拟结果表明,模具外角Ψ>0°～30°的范围内,等效应变的分布较为均匀;当模具外角Ψ>30°时,等效应变的分布越来越不均匀;当模具外角Ψ=0°～90°范围内逐渐增大时,试样的变形机理由单一剪切变形逐渐变为剪切变形与弯曲变形相结合的复合变形行为。为了验证模拟结果,对大尺寸纯铝进行了等通道转角挤压实验(模具内角Ф=90°,模具外角Ψ=30°),纯铝实验应变值的分布与大小和模拟应变值的分布与大小近似吻合。由光学显微组织可知,经ECAE挤压一次后,变形试样组织较为均匀,晶粒得到一定程度细化。     

等径角挤压制备AZ91D镁合金的组织与性能

研究了铸态AZ91D镁合金在等径角挤压（Equal Channel Angular Extrusion,ECAE）后的室温力学性能和微观组织特征。在力学性能方面,铸态AZ91D镁合金经过1道次ECAE变形后,室温力学性能（屈服强度、抗拉强度、延伸率、弹性模量）由86.3 MPa,146.3 MPa,1.84%,42.5 GPa分别提高到144.1MPa,222.8 MPa,3.49%,47.7 GPa;2道次后变为109.1 MPa,268.3 MPa,4.48%,48.9 GPa。在微观组织方面,挤压1道次后,由于枝状晶粒在等径道弯角处滑动和转动时发生破碎,AZ91D镁合金的晶粒和黑色共晶相Mg17Al12沿挤压方向拉长为条带状;挤压2道次后,黑色共晶相开始部分回溶,共晶相有所减少且呈非连续分布。     

等通道挤压Mg2Si增强ZK60镁合金的显微组织及力学性能

研究等通道挤压(ECAP)对ZK60+2Si镁合金显微组织、室温力学性能和高温抗蠕变性能的影响。结果表明,合金铸态组织主要由-Mg基体、Mg2Si相和MgZn相组成,等通道挤压可显著碎化原粗大汉字状Mg2Si相并使其趋于弥散分布,同时基体组织也得到细化。挤压4道次后,合金的室温抗拉强度由154.8MPa增加到270MPa,伸长率由4.5%增加到17.5%。挤压6道次后,合金的伸长率进一步增加到21%,而抗拉强度却下降至261MPa;合金的高温蠕变寿命由铸态20h延长到203h,稳态蠕变速率下降了约1个数量级,这主要是因为细小颗粒状MgSi相有效阻止了晶界滑移。     

Electron back-scattered diffraction and nanoindentation analysis of nanostructured Al tubes processed by multipass tubular-channel angular pressing

Microstructural evolution and mechanical properties of nanostructured 1060 aluminum alloy tubes processed by tubular-channel angular pressing (TCAP) process were investigated using electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM) and nanoindentation analyzes. EBSD scans revealed a homogeneous ultrafine grained microstructure after the third passes of the TCAP process. Apart from that the mean grain sizes of the TCAP processed tubes were refined to 566 nm, 500 nm and 480 nm respectively after the first, second and third passes. The results showed that after the three TCAP passes, the grain boundaries with a high angle comprised 78% of all the boundaries. This is in comparison to the first pass processed sample that includes approximately 20% HAGBs. The TEM inspection afforded an appreciation of the role of very low-angle misorientation boundaries in the process of refining microstructure. Nanoindentation results showed that hardness was the smallest form of an unprocessed sample while the largest form of the processed sample after the three passes of TCAP indicated the highest resistant of the material. In addition, the module of elasticity of the TCAP processed samples was greater from that of the unprocessed sample.     

Microstructural evolution and mechanical properties of Al–40 wt.%Zn alloy processed by equal-channel angular extrusion

The Al-based Al–40 wt.%Zn alloy was subjected to multi-pass equal-channel angular extrusion (ECAE) via route-A and route-B_C. Before and after ECAE processing, microstructural evolution, the tensile properties, impact toughness and fracture behavior of the alloy were investigated.ECAE processing caused to elimination of the as-cast dendritic microstructure and formed a structure consisting of elongated, ribbon shaped α-phase via route-A and mostly equiaxed α-phase via route-B_C. ECAE processing also caused plastic instability as necking at early onset of deformation. As a result of more effective mechanical mixing via route-B_C, softening and necking occurred more apparently. The tensile and yield strength of the alloy increased just after first pass and then slightly decreased with increasing number of passes. On the other hand, its elongation to failure and impact toughness increased with increasing number of passes in both routes. The increase obtained via route-A is more pronounced in both properties. Fracture behavior of the as-cast alloy changed from brittle to ductile mode after multi-pass ECAE. Elimination of dendritic as-cast structure with reduction of porosities and deformation-induced homogenization by the effect of ECAE processing increased the ductility and impact toughness of the alloy and caused formation of a fracture surface consisting of micro-voids and dimples which indicates of ductile fracture. Attained experimental results indicate that multi-pass ECAE processing is very effective in improving the tensile elongation and impact toughness of binary Al–40 wt.%Zn alloy.