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。     

AZ31镁合金铸坯均匀化退火

研究了一种新的均匀化退火工艺对AZ31镁合金铸坯组织转变和成分均匀化的影响,保温温度为530、540和550 ℃以及保温时间为30、60和90 min.结果表明,AZ31镁合金在固相线温度以下应尽可能提高退火温度,同时缩短退火时间可使铸坯达到较好的均匀化效果,消除大部分枝晶偏析,γ-Mg_(17)Al_(12)相在α-Mg基体上呈细小的颗粒状分布; AZ31镁合金铸锭的优化退火工艺为540 ℃保温60 min.     

正挤压对铸态AZ31镁合金组织与性能的影响

为了研究塑性变形对铸态镁合金组织和性能的改善作用,用铸态AZ31镁合金进行了正挤压试验,并测试了原始试样和变形后试样的组织和性能.结果表明,正挤压可使铸态AZ31合金晶粒显著细化;挤压后抗拉强度和伸长率比挤压前分别提高22%和100%;随挤压温度升高,挤压所得试样的抗拉强度明显下降,但伸长率变化幅度较小;随挤压比的升高,挤压所得试样的伸长率和抗拉强度均明显升高.     

AZ31镁合金挤压棒退火组织和织构的演变

试验研究了退火温度对AZ31镁合金挤压棒组织和织构的影响.结果表明:铸态镁合金挤压后,初始强点织构向(80°,90°,0°)面聚集,主要织构组分强度提高.对热挤压后的AZ31镁合金进行退火,可以细化晶粒,使组织均匀,300℃退火时平均晶粒尺寸5μm为最小;随着退火温度的升高,形变织构(80°,90°,0°)逐渐减弱,再结晶织构(0°,90°,0°)和(90°,55°,0°)逐渐增强,300℃退火之后二者均被弱化,400℃退火之后取向分布漫散度增大.     

退火工艺对AZ31镁合金组织与性能的影响

研究了热处理工艺对AZ31镁合金轧制板材的显微组织和力学性能的影响。试验表明，AZ31镁合金轧制板材在退火过程中发生了静态再结晶现象，200℃时可以观察到再结晶现象，再结晶温度为200～250℃。分析了退火温度和退火时间对合金显微组织、晶粒尺寸、硬度以及力学性能的影响规律。     

退火工艺对AZ31镁合金组织及耐磨性能的影响

通过对AZ31镁合金采用不同的退火工艺,利用金相显微镜观察、摩擦磨损试验,研究了不同退火工艺对AZ31镁合金显微组织和耐磨性的影响。结果表明,最佳的退火工艺为280 ℃×80 min。此条件下会形成再结晶组织,使晶粒细化,从而改善耐磨性,材料的耐磨性与前工艺相比,有明显提高。     

加工参数对铸态AZ31B镁合金热变形行为及组织演变的影响

借助热压缩实验研究了变形温度、应变速率和变形量对铸态AZ31B镁合金热变形行为及组织演变的影响规律。结果表明:(1)峰值应力随着应变速率的降低和温度的升高而减小,主要的形核机制为晶界弓出形核、亚晶旋转形核、孪生诱发形核,以及连续再结晶;(2)低于400℃变形时,温度的升高有利于再结晶的发生及晶粒细化;高于400℃时,晶粒尺寸开始迅速增大;(3)在小于等于400℃变形时,低速率0.1 s~(-1)更有利于再结晶晶粒细化;当变形温度高于400℃时,中速率1 s~(-1)更有利于再结晶晶粒细化;(4)高温低速率变形时,变形量主要影响晶粒尺寸,而高温高速率变形时,变形量主要影响动态再结晶程度。     

熔体温度对AZ31B镁合金铸态组织及力学性能的影响(英文)

采用自制的电阻炉研究熔体温度对AZ31B镁合金凝固组织与拉伸性能的影响。结果表明:在温度低于850℃水冷时,金属型AZ31B镁合金铸锭等轴枝晶的尺寸随着熔体温度的升高呈直线下降,超过850℃后变化不大。组织中第二相呈现出先细化后粗化的变化规律。AZ31B镁合金试样的抗拉强度、伸长率和屈服强度随着熔体温度的提高而先快速增大后略有减小,熔体温度为850℃时试样的抗拉强度达到260MPa,屈服强度达到75.4MPa,伸长率达到27.57%,比熔体温度为750℃时的分别提高了15%、13%和61%。DSC分析表明,升高熔体温度使凝固开始点温度降低,临界晶核半径减小,从而增加了熔体中的过冷度,提高了熔体中非均匀形核率,是镁合金晶粒细化和拉伸性能提高的主要原因。     

热轧及退火处理对AZ31镁合金板材组织的影响

采用单向轧制的方法制备了AZ31镁合金板材,分析了不同轧制温度、道次变形量等工艺参数对组织性能的影响规律.研究结果表明,在多道次轧制时,当轧制温度为400℃,单道次变形量为25%时,所得到的AZ31镁合金板材经过热处理后的晶粒细小且均匀,板材平均晶粒尺寸达到6 μm;当轧制温度为400℃,单道次变形量为35%时,得到的板材平均晶粒尺寸为10μm.在轧后热处理时,当热处理温度低于150℃,且保温时间为30 min的情况下,轧制板材再结晶不完全;当热处理温度在250～300℃之间时得到的板材平均晶粒尺寸为5μm;当热处理温度超过350℃时轧制板材再结晶组织粗大而且孪晶组织消失.当热处理温度为320℃,且保温时间为15 min时,开始发生再结晶,再继续增加保温时间到120 min时对组织没有明显影响.     

铸态AZ31B镁合金热压缩流变应力

在Gleeble-1500热模拟机上,对铸态AZ31B镁合金在温度280℃～440℃和应变速率0.001s-1～0.1s-1条件下,研究其流变应力行为.结果表明:铸态AZ31B镁合金在高温下表现出较低的流变应力,其真应力-应变曲线表现出明显的动态再结晶特征;可采用Zener-Hollomon参数的双曲正弦函数来描述AZ31B镁合金高温变形时的流变应力行为;获得流变应力σ解析表达式中的A、α和n值分别为7.59×109s-1、0.015MPa-1和4.91,激活能Q为141.6kJ/mol.     

不同退火条件下AZ31镁合金的组织和硬度分析

研究了AZ31镁合金在不同的去应力退火和完全退火结合条件下组织和硬度变化.结果表明:镁合金在250～280℃退火时,晶粒先增大后减小,最终晶粒细小且均匀;但保温时间较长,退火温度为300～350℃时,晶粒尺寸比较稳定;在400℃退火处理后,短时间内晶粒立即出现异常长大现象,晶粒粗大且不均匀,合金性能较差.退火处理的最佳温度为280～350℃.退火处理温度对AZ31镁合金的硬度值有显著影响,但退火处理时间的影响却不明显.     

Paint-bake response of AZ80 and AZ31 Mg alloys

Aging behaviors of extruded and rolled AZ80 and AZ31 Mg alloys were investigated under conditions similar to the paint-bake cycle currently used in automotive industry.Artificial aging at 170℃ from 0.5 to 12 h was conducted on solution-treated specimens to study the effects of aging on mechanical properties.SEM observations and EDS data show thatβ-phase of Al12Mg17 precipitates continuously or discontinuously fromα-Mg matrix and distributes along grain boundaries of the AZ80 alloy during artificial aging.Data of tensile tests and Vickers hardness tests show that an optimum mechanical property is achieved after baking at 170℃ for 6-8 h when Vickers hardness,tensile strength,and elongation are increased by 6.35%,15.30%,and 7.88%,respectively, while the AZ31 alloy does not exhibit significant hardening behavior over the aging period.     

铈对AZ31镁合金显微组织和力学性能的影响

在AZ31合金中添加0、0．2％、0．5％和1％（质量分数）的铈（Ce）制备了4种合金,研究不同Ce含量和合金变形状态对力学性能和显微组织的影响。试验表明,添加Ce元素后,形成的Al4Ce对合金有强化作用,但其铸态组织仍然粗大,经过轧制及退火后,合金的组织得到改善。力学性能测试结果表明,轧制态合金强度随Ce含量的增加而上升,伸长率亦有所提高,300℃退火1h后,强度比轧制态有所降低,伸长率提高较大。含0．5％铈的3号合金综合力学性能最好,屈服强度为168MPa,抗拉强度达到255MPa,伸长率为22％。     

Superplasticity of fine-grained AZ31 Mg alloy sheets

Superplastic mechanical properties of fine-grained AZ31 Mg alloy sheets in the temperature range of 250 - 450 ℃ and strain rate range of 0.7 × 10-3- 1.4 × 10-1 s-1 were investigated by uniaxial tensile tests. The microstructure evolution during the superplastic deformation of AZ31 Mg alloy was examined by means of metallurgical microscope and transmission electronic microscope (TEM). It is shown that, fine-grained AZ31 Mg alloy starts to exhibit superplasticity at 300 ℃ and the maximum elongation of 362.5% is obtained at 400 ℃ and 0.7× 10-3 s-1.The predominate superplastic mechanism of AZ31 Mg alloy in the temperature range of 300 -400 ℃ is grain boundary sliding (GBS). Twinning caused by pile-up of dislocations during the early stage of superplastic deformation is the hardening mechanism, and dynamic continuous recrystallization (DCRX) is the important softening mechanism and grain stability mechanism during the superplastic deformation of the alloy.     

Microstructure evolution and mechanical behavior of AZ31 Mg alloy processed by equal-channel angular pressing

AZ31 Mg alloy bar was subjected to 8-pass equal-channel angular pressing(ECAP) at 623 K. Microstructure evolution was observed by optical microscopy(OM) on cross section and X-ray diffraction analysis. The room temperature mechanical properties of the ECAP processed specimens were also investigated. A fine-grained structure with an average sub-grain size of 9 μm is obtained after 7 ECAP passes. XRD analysis indicates that after ECAP, in placing of planes and become the dominant directions that are favourable for grain refinement. ECAP processed AZ31 Mg alloy exhibits significant improvement in elongation but decrease in strength. The elongation of the specimen increases continuously up to 2 passes and then remains stable at further passes. This improvement can be related to the evolution of crystallographic texture and the scattered orientation of the basal plane (0001).     

AZ31铸造镁合金的物相和显微组织

使用XRD、OM、SEM-EDX以及WD/ED-CMA等技术研究了AZ31铸造镁合金的物相、显微组织及主要元素分布.结果表明：AZ31铸造镁合金由α-Mg基体、共晶体以及弥散分布于晶内的细小析出相组成,是一种典型的铸造离异共晶体组织.α-Mg晶粒为粗大的等轴晶,颗粒直径约为150μm;共晶体由α-Mg与β-Mg17（AlZn）12组成,沿晶界呈不连续网状分布,β-Mg17（AlZn）12为多角形块状和片层类似粗珠光体状;元素Al、Zn主要富集在晶界上,与Mg形成β-Mg17（AlZn）12相,元素Si、Mn与Mg、Al形成Mg2Si、AlMn析出相,弥散分布于晶内,有少量Si固溶于α-Mg基体中,引起α-Mg基体的X射线衍射峰向高角度偏移,且其晶格常数有所减小.     

AZ31镁合金轧制变形后组织性能研究

本文研究了不同轧制变形量和轧制速度对AZ31镁合金板材微观组织和力学性能的影响。轧制变形可显著细化AZ31镁合金板材的晶粒尺寸并提高其综合力学性能。当轧制速度为5m/min,轧制变形量为50%时,板材平均晶粒尺寸最细可达到9μm,其抗拉强度、屈服强度和延伸率分别提高到280MPa、180MPa和30%以上,同时探讨了AZ31镁合金屈服强度与晶粒大小之间的关系。在大量AZ31镁合金轧制相关文献和本文一系列实验研究的基础上,对比分析了不同轧制工艺对AZ31镁合金综合力学性能的影响。研究表明,本文所采用轧制工艺可显著提高AZ31镁合金板材的综合力学性能,同时降低板材轧向和横向的各向异性。     

Effect of Vanadium Nitride (VN) Particles on Microstructure and Mechanical Properties of Extruded AZ31 Mg Alloy

The effect of vanadium nitride (VN) particles additives on microstructure and mechanical properties of the extruded AZ31 Mg alloy was systematically investigated. The experimental results revealed that the addition of 0.5 wt% VN decreased the average grain size of AZ31 Mg alloy from 6.4 to 4.9 µm. With the increase in VN content, the refining effect would weaken because excessive VN particles would negatively affect the dynamic recrystallization process of the alloys. The scanning electron microscopy and energy-dispersive spectroscopy indicated that AlN, VN and Al-V-N particles with different morphologies were distributed in the streamline along the extrusion direction during the extrusion process. The mechanical properties of AZ31 Mg alloy vary with the addition of VN. The extruded AZ31 + 0.5 wt% VN Mg alloy possesses an excellent combination of high strength and ductility. The yield strength and ultimate tensile strength of the extruded AZ31 + 0.5 wt% VN Mg alloy were increased without sacrificing ductility. This is mainly due to the grain refinement caused by double-heterogeneous nucleation particles. With a further increase in VN content, the presence of excessive VN particles increases the stress concentration, and the initiation source of microcracks in the alloy during alloy deformation makes the cracks more easily propagated and results in a decrease in the ductility of the extruded alloy.