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。     

ICAE对汽车用AZ31镁合金板材组织性能影响实验研究

汽车轻量化需要细化金属晶粒,提高板料综合性能,因而研究并优化模具结构、改善变形过程成为AZ31镁合金板材塑性成形工艺当前的研究内容。提出了减径通道转角(ICAE)挤压工艺。试验研究了ICAE制备的200 mm×2 mm的AZ31镁合金板材组织与性能,结果表明:在ICAE过程中,通过晶粒破碎和动态再结晶可以显著细化合金晶粒,挤压后的平均晶粒尺寸约为2~4μm,且晶粒大小均匀,力学性能较传统方法成形的挤压板材大幅度提高。     

挤压变形对MBl5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。     

大尺寸ZK60镁合金型材挤压成形数值模拟及实验研究

应用HyperXtrude有限元模拟软件,对大宽厚比ZK60镁合金型材正挤压成形过程进行了数值模拟,优化了模具结构,研究了不同挤压速度对型材成形效果的影响。对模拟得到的速度、位移、应变和温度场进行分析,优化了挤压工艺。在挤压温度为350℃,挤压速度为20mm·s-1下进行正挤压试验,成功挤出宽度225mm,厚6mm的ZK60镁合金型材。型材横截面微观组织为动态再结晶组织,晶粒沿变形方向被拉长,变形中的温度场和金属流动方向是影响微观组织的主要因素。对该型材采用不同热处理工艺处理后进行力学性能测试。结果表明,该型材经250℃保温2h的退火工艺可以获得较高的综合力学性能。     

镁合金新型复合挤压的有限元和实验研究

针对镁合金的棒材的工业化制备和加工,提出了一种新型的镁合金复合挤压方法,将正挤压(Extrusion)和剪切(Shear)结合(简称ES),建立了ES挤压的三维有限元热力耦合模型及条件,模拟了ES挤压的流动网格、累积应变演化,设计并制造了适合于卧式挤压机上的ES挤压模具,进行了ES工艺实验。数值模拟结果表明,ES挤压可以显著提高镁合金变形过程的累积应变;试验结果表明,ES挤压可以得到尺寸很小的动态再结晶晶粒,并改善了组织均匀性;理论分析表明,ES挤压过程镁合金具有多级动态再结晶的特性,可以逐步有效的细化微观组织。ES挤压在模具结构、工艺参数合理的条件下可以大大细化镁合金微观组织,并具有工业生产的实用性。     

ZK60镁合金管材热挤压成形组织演变规律

采用数值模拟和试验方法研究了变形镁合金ZK60管材挤压成形组织演变规律。根据材料热模拟试验结果,得到了ZK60镁合金动态再结晶组织演变的Yada模型中的相关系数。结果表明,当挤压速度增大时,挤压管材晶粒尺寸减小,变化规律接近线性。当挤压温度增大时,挤压管材晶粒尺寸增大。挤压比增大时,晶粒尺寸减小。晶粒尺寸数值模拟结果与试验结果吻合,最大相对误差小于16%。当温度在300～360℃时,ZK60镁合金发生了完全动态再结晶,晶粒较小且组织均匀,平均晶粒尺寸是原始晶粒尺寸的38%。     

AZ31镁合金挤压板坯的二次变形行为

采用Gleeble-3500热模拟试验机对AZ31镁合金挤压板坯进行平面应变压缩实验,研究镁合金二次变形条件下的热变形行为。结果表明,AZ31镁合金挤压板坯二次变形中发生明显的动态再结晶,进一步细化了再结晶晶粒,且二次变形削弱了挤压板坯的(0002)基面织构强度。DEFORM 3D有限元模拟结果表明,当应变速率一定时,变形温度是决定再结晶晶粒大小的主要因素,而当变形温度一定时,高应变速率所引起的显著温升不利于应变累积,因而再结晶晶粒细化效果并不明显。     

AZ31镁合金的热模拟和挤压

采用Gleeble-1500D材料热模拟实验机、630T挤压机和金相显微镜研究了在塑性变形中挤压变形对AZ31镁合金管材微观组织的影响规律,在挤压之前对镁合金铸锭进行了均匀化处理.研究结果表明:AZ31镁合金热挤压时发生了动态再结晶,材料组织比铸态时细化;随挤压比的增大,晶粒细化程度增加,平均晶粒尺寸为19～37μm.     

挤压比对AZ31镁合金组织结构的影响

试验研究了挤压比对AZ31镁合金组织结构的影响.结果表明,258℃挤压变形镁合金在形变初期容易出现孪晶,再结晶晶粒一般出现在晶界和孪晶附近.挤压比小时动态再结晶晶粒平均尺寸为2 μm,动态结晶细化了晶粒.随着挤压比增大,晶粒尺寸减小,组织趋于均匀.挤压比达到16时,动态再结晶基本完成.挤压比为25时,能得到晶粒细小且均匀的组织,平均晶粒尺寸为7.3 μm.     

大口径厚壁管道热挤压成形过程微观组织模拟及实验研究

针对某型核能发电用P91大口径厚壁无缝管道进行了不同挤压比条件下的垂直正挤压成形过程缩比数值模拟,研究了管道微观组织在挤压过程中的演变规律。研究表明:挤压过程中金属温度场变化和局部变形速率对管道晶粒组织演变具有重要影响。相同工艺因素条件下,平均晶粒尺寸在轴向上从变形区到挤出端逐渐递增,而在径向上从管道内侧到外侧逐渐递减;管道内侧的动态再结晶百分数高于外侧;管道金属在轴向比径向有更高的动态再结晶发生率,且动态再结晶晶粒尺寸比径向更小。管道的平均晶粒尺寸随着挤压比的增加呈减小的趋势,挤压比越大,动态再结晶发生的越充分,越利于晶粒细化。进行了与数值模拟相配套的缩比挤压成形实验,并针对获得的样件分别进行了金相实验和晶粒度评定,所测得的平均晶粒尺寸变化规律与数值模拟基本吻合,证明了数值模拟的正确性,同时验证了增大挤压比对管道晶粒细化具有重要的促进作用。     

热挤压对铸态Mg-1Zn-0.3Zr-1Y-2Sn镁合金组织和性能的影响（英文）

通过光学显微镜(OM)、扫描电镜(SEM)、浸泡实验、析氢实验、电化学试验、拉伸试验等方法,研究了不同挤压温度(340、360、380、400℃)下,热挤压对铸态Mg-1Zn-0.3Zr-1Y-2Sn合金组织和性能的影响。结果表明:热挤压后,合金的第二相沿挤压方向破碎成颗粒,微观组织中存在动态再结晶和变形晶粒。随着挤压温度的升高,第二相的含量变化较小,动态再结晶晶粒尺寸逐渐增大。热挤压后,合金的力学性能得到改善,但其耐腐蚀性最终减弱。热挤压处理可以在腐蚀的早期阶段提高合金的耐腐蚀性能,但随着腐蚀的进行,在后期合金的耐蚀性能会降低。当热挤压温度为360℃时,合金具有较好的力学性能和耐腐蚀性能。     

An extrusion−shear−expanding process for manufacturing AZ31 magnesium alloy tube

A new severe plastic deformation method for manufacturing tubes made of AZ31 magnesium alloy with a large diameter was developed, which is called the TCESE (tube continuous extrusion?shear?expanding) process. The process combines direct extrusion with a two-step shear?expanding process. The influences of expanding ratios, extrusion temperatures on the deformation of finite element meshes, strain evolution and flow velocity of tube blanks during the TCESE process were researched based on numerical simulations by using DEFORM-3D software. Simulation results show that the maximum expanding ratio is 3.0 in the TCESE process. The deformation of finite element meshes of tube blanks is inhomogeneous in the shear?expanding zone, and the equivalent strains increase significantly during the TCESE process of the AZ31 magnesium alloy. A extrusion temperature of 380 °C and expanding ratio of 2.0 were selected as the optimized process parameters from the numerical simulation results. The average grain size of tubes fabricated by the TCESE process is approximately 10 µm. The TCESE process can refine grains of magnesium alloy tubes with the occurrence of dynamic recrystallization. The (0001) basal texture intensities of the magnesium alloy tube blanks decrease due to continuous plastic deformation during the TCESE process. The average hardness of the extruded tubes is approximately HV 75, which is obviously improved.     

AZ91镁合金的挤压和析出硬化行为(英文)

挤压比为4:1,将铸态AZ91镁合金分别在250,300和350℃下进行挤压,随后进行析出硬化处理(T6)。经过热挤压和析出硬化处理后,铸态AZ91镁合金中粗大的和偏析Mg17Al12析出相被细化并均匀分布在α-镁基体中。在不同的挤压温度下合金中发生了部分或全部动态再结晶。经挤压后,该合金的极限抗拉强度从铸态的190MPa增加到570MPa。AZ91镁合金的时效硬化特征与晶粒尺寸有关。在250、300和350℃下以4:1的挤压比挤压该合金后,获得峰值硬度的时效时间分别为35、30和20h。SEM观察到在AZ91基体中存在均匀细小的Mg17Al12析出相。     

Microstructure and Corrosion Behavior of the As-Extruded Mg-4Zn-2Gd-0.5Ca Alloy

In order to study the corrosion resistance of extruded magnesium alloys,the Mg-4 Zn-2 Gd-0.5 Ca alloy was extruded at the speed of 0.01-0.1 mm/s with the temperature of 280-360℃in present study.Hot extrusion results show that the volume fraction of precipitates(V_(pre)),V_(DRX)(the dynamic recrystallization rate) and the average size of DRXed grain(d_(DRX)) decrease with the decrease in extrusion speed,and the corrosion rate of the alloy also shows a downward trend.On the contrary,the values of V_(pre),V_(DRX) and d_(DRX) increase with the increase in extrusion temperature,and the corrosion resistance of Mg-4 Zn-2 Gd-0.5 Ca alloy decreases.When the extrusion speed is 0.01 mm/s and the extrusion temperature is 280℃,the alloy has the best corrosion resistance.The corrosion of extruded Mg-4 Zn-2 Gd-0.5 Ca alloy occurs preferentially on the magnesium matrix around W and I phases in the DRXed zone.With the further corrosion,the corrosion continues to spread along the phase,and the corrosion area gradually increases.Galvanic corrosion plays a leading role in the corrosion process.Moreover,there are a large number of basal plane textures in the unDRXed region,which is conducive to improving the corrosion resistance of magnesium alloys.In addition,the decrease in grain size also makes the corrosion of magnesium alloy more uniform.     

Microstructure characterization and effect of extrusion temperature on biodegradation behavior of Mg-5Zn-1Y-xCa alloy

Microstructure and biodegradation behavior of as-cast and hot extruded Mg-5Zn-1Y alloy containing different amounts of calcium (0.0%, 0.1%, 0.5%, and 1.0%, mass fraction) were explored. The extrusion process was conducted at three different temperatures of 300, 330, and 370 °C. Chemical composition, phase constitution, microstructure, and biodegradation behavior of the alloys were investigated. The macro- and micro-scopic examination revealed that the addition of Ca refines the grain structure and forms an intermetallic phase, Ca₂Mg₆Zn₃. The hot extrusion process resulted in breaking the intermetallic phases into fine particles routed to the extrusion direction. Moreover, dynamic recrystallization happened in almost all alloys, and more bimodal microstructure was formed in the alloys when the alloys were extruded at 370 °C. Polarization curves showed no passive region, which indicated that active polarization dominated in the alloys; therefore, grain refining through Ca addition and dynamic recrystallization over hot extrusion operation increased biodegradation rate. The results show that the as-cast Mg-5Zn-1Y-0.1Ca alloy provides the highest corrosion resistance, and the extruded Mg-5Zn-1Y-0.5Ca alloy at 300 °C shows the lowest biodegradation rate among the extruded alloys. Therefore, hot extrusion does not always improve the biodegradation behavior of magnesium alloys.     

挤压速度和电磁铸造锭坯对AZ31镁合金板材组织和性能影响

文章研究挤压条件下挤压速度和电磁铸造锭坯对挤压态AZ31镁合金板材组织和性能的影响。研究结果发现,挤压速度比较低时,板材晶粒尺寸小,板材的表面质量比较好;随着挤压速度的降低,抗拉强度、屈服强度和延伸率都有一定的提高。由于镁合金是HCP的晶体结构,同时对挤压速度非常敏感,对变形均匀性影响比较大,因此造成挤压板材的内外晶粒大小不均。在电磁场的作用下,溶质在晶内的固溶度增大,同时晶粒大小也比常规铸造的细小,因此电磁铸造的锭坯经挤压机挤压后,挤压板材的晶粒尺寸比较细小,且强度和塑性都有所提高。     

采用挤压剪切工艺制备细晶高强韧镁合金

设计一种新型挤压剪切(ES)复合工艺以制备细晶高强韧镁合金.利用有限元软件Deform-3D,通过正交模拟实验对ES模具的结构参数进行优化,并采用ES模具对Mg?3Zn?0.6Ca?0.6Zr(ZXK310)合金进行成形.结果表明,优化的ES模具结构参数为挤压角ɑ=90°、挤压段高度h=15 mm以及内圆角半径r=10...     

剪切角对挤压-剪切法制备AZ31镁合金组织和压缩性能的影响

采用挤压-剪切法(ES)在不同剪切角(150°、135°和120°)下制备了AZ31棒材。采用ES工艺制备的棒材,包括直接挤压和后续剪切两部分。随后采用光学显微镜、扫描电镜和电子背散射衍射(EBSD)等方法研究了具有双峰晶粒结构的AZ31镁合金的显微组织演变,从取向分布图中可清晰的观察到细晶粒包围狭长变形粗晶的混晶结构,且大晶粒区域的占比会随应变的增加而增大。整体来看,因为应变量和动态再结晶分数都会随着剪切角的减小而增加,导致大晶粒的占比增大,而小晶粒尺寸增加。室温压缩实验中,随着剪切角的减小,屈服强度和峰值强度逐渐增大。此外,ES挤压的基面极图也会随着剪切角度的不同发生变化。     

Influence of Hot Extrusion Temperature on the Microstructure and the Mechanical Properties of (ABOw + WO3p)/Al Hybrid Composites

The (ABOw + WO₃p)/Al hybrid composite was fabricated by squeeze casting and subsequently hot extruded at temperatures that varied from 440°C to 560°C. The microstructures of extruded composites were examined by scanning electron microscopy and transmission electron microscopy techniques. The results show that ABOw aligns along the extrusion direction after the hot extrusion process. The aspect ratio of ABOw in extruded composites is lower than that of as-cast composite. The aspect ratio of ABOw in extruded composites increases with the increase of extrusion temperature. The larger WO₃p particles are broken into smaller particles during the extrusion process. The transmission electron microscopy (TEM) images show that hot deformation leads to high dislocation density at a lower deformation temperature and leads to grain recovery and recrystallization at a higher deformation temperature. The strength of extruded composites increases first and then decreases with the increase of extrusion temperature, and it reaches maximum value at 500°C. The elongation of extruded composites increases with the increase of extrusion temperature.     

挤压比对AZ80镁合金组织及性能的影响

在温度为390℃时,对AZ80镁合金在工业用压力机上采用15、30、45、60和75五个挤压比进行正挤压,并对不同挤压试样进行研究分析.结果表明:随挤压比的增加,即变形量的增加,在变形过程中新晶粒所占体积分数越来越大,且在一定条件下动态再结晶可以重复进行,因此使晶粒得到明显细化,有效提高了合金综合性能.随挤压比升高,强度有升高趋势,其抗拉强度在挤压比为60时达390MPa,伸长率达11%.