Impact of asymmetry deformation on microstructure and mechanical properties of AZ31B alloy sheets deformed by on-line heating rolling

The effect of asymmetry deformation on microstructure and mechanical properties of AZ31 sheet was investigated in the present paper. Two AZ31 sheets were rolled together with an on-line heating rolling mill and separated from each other afterwards. For each sheet, the strain on both surface during rolling was asymmetry and this rolling method is called asymmetry rolling (AR) in present work. For comparison, symmetry rolling (SR) was also carried out on the same rolling mill that only one sheet was rolled in one pass. The sheets deformed by AR showed more homogeneous microstructure with higher recrystallization level and symmetry distributional basal texture. Moreover, SR sheets showed many narrow shear bands which distributed as “V” shape along rolling direction, while less shear bands with wider size are observed in AR sheet. The shear bands in AR sheet distributed as a line and across the entire thickness of the sheet, resulting in layered bimodal structure. Based on the unique microstructure and texture characteristics, AR sheet has lowest mechanical property anisotropy and a good balance of strength and elongation.     

基于三点支撑法镁合金刚度特性的实验研究

镁合金的弯曲刚度是其工程应用的重要考核指标之一.通过三点支撑法分别研究了厚度为2.16mm与3.66mm的AZ31和AZ31B镁合金板的杨氏模量及弯曲刚度.结果表明,AZ31和AZ31B镁合金的杨氏模量和弯曲刚度相差不大.杨氏模量的值介于41.74~45.1GPa之间,弯曲刚度的值介于28.4~30.8GPa之间.对与3.66mm厚镁合金试件具有相同面密度的铝合金和钢质试件做了相同的研究,结果表明,镁合金板具有更高的抗弯系数.同时AZ31镁合金的比刚度为钢板比刚度的93.2%,比铝合金板高20.6%,AZ31B的比刚度比AZ31的略低.因此,镁合金是最合适的轻量化设计材料.     

镁合金板材温热冲压成形热力耦合数值模拟

采用Gleeble3500热模拟试验机进行单向拉伸试验,获取了材料的力学性能参数,分析了AZ31镁合金板材的力学性能特点.采用热力耦合技术对镁合金板材温热冲压过程中的温度场进行了数值模拟,研究了冲压过程中温度场的分布规律,并对差温拉延工艺进行了分析.结果表明:差温拉延工艺可以提高镁合金板材的温热成形性能;采用热力耦合技术的数值模拟更能反映AZ31镁合金板材的温度敏感特性.     

非线性组合硬化条件下镁合金板料变形回弹预测

变形回弹作为金属板料成形的主要缺陷之一,如何提高变应变路径条件下的回弹预测精度一直是研究者们面临的难题.本文针对镁合金变形特点,提出了同时考虑同向硬化、动态硬化和屈服圆畸变的本构模型.以0.8mm厚AZ31B镁合金板料为研究对象,施加不同预拉伸后进行弯曲变形试验,观察了不同预变形对回弹规律的影响.同时结合有限元分析ABAQUS-Explicit(Vumat)和ABAQUS-Implicit(Umat)对板料的变形及回弹过程进行模拟仿真,对比试验与模拟结果,验证动态硬化对于镁合金板料变形回弹的重要影响.     

异径轧制对AZ31镁合金薄带微观组织的影响

考虑到轧制镁合金薄带板形的控制精度要求,采用小辊径同径轧制和异径轧制工艺分别制备了0.5,1.0 mm的AZ31镁合金薄带,研究不同工艺过程中板材内部晶粒微观组织的变化规律以及同径轧制与异径轧制在轧制过程中的对称性问题.结果表明:0.5 mm异径轧制和同径轧制板带的晶粒尺寸分别为8.8和10.1μm,1.0 mm的分别为13.6和16.7μm.0.5 mm的异径轧制与同径轧制的单元等效塑性应变最大值分别为0.42和0.29,1.0 mm的分别为0.75和0.66,与实验结果相符.0.5 mm同径轧制的特征节点在板带上中下部的等效米塞斯应力和剪切应力分布对称,异径轧制的分布非对称.0.5 mm板带经过250,300,350℃退火1 h后,异径轧制的晶粒长大较缓慢,同径轧制的晶粒长大较快.350℃下,异径轧制的晶粒尺寸为9.8μm,同径轧制的为24.9μm.     

Characteristics of AZ31 Mg alloy joint using automatic TIG welding

The automatic tungsten-inert gas welding (ATIGW) of AZ31 Mg alloys was performed using a six-axis robot. The evolution of the microstructure and texture of the AZ31 auto-welded joints was studied by optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction. The ATIGW process resulted in coarse recrystallized grains in the heat affected zone (HAZ) and epitaxial growth of columnar grains in the fusion zone (FZ). Substantial changes of texture between the base material (BM) and the FZ were detected. The {0002} basal plane in the BM was largely parallel to the sheet rolling plane, whereas the c-axis of the crystal lattice in the FZ inclined approximately 25° with respect to the welding direction. The maximum pole density increased from 9.45 in the BM to 12.9 in the FZ. The microhardness distribution, tensile properties, and fracture features of the AZ31 auto-welded joints were also investigated.     

AZ31温轧过程变形区温度模拟

AZ31镁合金薄板温轧过程中引起变形区温度波动的因素较多,因此变形区温度的精确预测是保证轧制工艺及产品质量的关键.本文利用有限元数值模拟软件针对AZ31镁合金薄板温轧过程变形区温度进行了数值模拟,给出了轧辊及轧件的物性参数及模拟的初始条件和边界条件,确定了影响变形区温度的5个关键因素为轧辊温度、轧件温度、轧件厚度、轧制速度及压下率.通过5水平的模拟正交实验方法获取模拟数据,回归了变形区温度数学模型,最后通过一组温轧模拟实验数据测试了数学模型计算精度.     

微观组织和织构对H65黄铜带材折弯性能的影响

电子产品关键部件小型化对黄铜合金带材折弯性能提出了更高的要求。研究了微观组织和织构对H65黄铜带材折弯性能的影响规律和影响机制。结果表明：带材平行于轧向折弯较垂直于轧向折弯更易于产生表面褶皱和裂纹,且随着折弯半径的减小,折弯性能降低。折弯变形过程中带材外表面易形成剪切带,所产生的剪切变形是造成表面褶皱和开裂的主要原因。微观组织不均匀、较强的Brass织构易导致带材折弯过程中产生剪切变形,造成带材折弯性能下降。通过调控热处理工艺来调整带材织构,减少或抑制剪切带的产生,能够提升带材的折弯性能。     

锡酸钠添加剂改善镁合金腐蚀及放电性能的研究

采用电化学方法探究了不同浓度锡酸钠添加剂对AZ31B镁合金在MgSO4-Mg(NO3)2(0.14 mol/L MgSO4,1.86 mol/L Mg(NO3)2)电解液中的腐蚀以及电化学放电行为的影响.结果表明,镁合金在含有1 mmol/L锡酸钠添加剂的溶液中具有最大的极化电阻值、最短的滞后时间和最低的电压降.采用电...     

连续流变成形过程中热流耦合场对合金组织的影响

为优化连续流变成形制备AZ31镁合金材料的工艺条件,利用有限元法模拟出了其在不同浇注温度条件下的速度场和温度场,并通过实验验证了模拟结果,分析了热流耦合场对合金组织的影响.结果表明:连续流变成形技术制备AZ31半固态合金的过程中,合金运动速度由靴侧到轧辊侧呈线性递增,在近轧辊处出现速度最大值,合金与靴接触边界速度为零;合金温度场由浇口到辊-靴型腔出口温度逐渐降低,并且等温线向轧辊侧偏离;合金出口温度与浇注温度基本呈线性的正比例关系变化,且模拟出的最佳浇注温度范围为730～770℃.     

AZ31B镁合金I型材室温弯曲成型研究

由于镁合金AZ31B材料在拉伸与压缩时的力学性能差异,使AZ31B型材在室温下成型规律很难掌握.文章以AZ31B镁合金I型材为研究对象,通过对I型材弯曲过程的数值分析,研究了I型材成型过程与加强筋的高度与厚度的关系,同时对成型过程中的受力、回弹现象及翘曲做了深入的分析,得出了对工程有实用性的结论,可以指导工程实际.     

Mechanical behavior and microstructure evolution for extruded AZ31 sheet under side direction strain

AZ31 magnesium alloy sheets were prepared by a conventional extrusion (CE) and a novel integrated extrusion with side direction strain (SE). The microstructure characterizations, crystallographic texture and mechanical property tests were carried out and compared between the extruded Mg alloy sheets processed by CE and SE. The results indicated that the SE sheets exhibited an excellent combination of strength and ductility. To reveal the side strain effect, the finite element model was employed to investigate the effective stress and strain behavior of the AZ31 magnesium alloy sheets during CE and SE processes. It was found that the SE process was effective in weakening the stress and strain concentration. This implied that it developed an additional side direction strain through the sheet thickness during the hot extrusion. Meanwhile, the side strain shear paths could promote the local accumulation of dynamically recrystallized grains and increase the random high-angle boundaries to achieve weak (0002) basal texture. Important factors including the side strain path and extrusion parameters need to be taken into account to understand the deformation mechanism and microstructure evolution.     

植酸改性对AZ31镁合金表面细胞黏附性能的影响

用浸没法在AZ31镁合金表面制备植酸涂层,用携带能谱仪的扫描电子显微镜研究了表面涂层的化学组成和形貌,并用直接法和间接法分别在植酸改性前后的镁合金表面培养细胞,检测细胞存活率,考查人骨肉瘤细胞在植酸改性前后镁合金表面的黏附能力。结果表明：在镁合金表面形成均匀的植酸涂层,植酸改性前后镁合金对细胞存活率影响相近,但细胞在植酸改性前后镁合金表面的黏附能力存在显著差异,植酸改性可有效改善AZ31镁合金的细胞黏附性能。     

Effects of the types of overlap on the mechanical properties of FSSW welded AZ series magnesium alloy joints

The effects of the types of overlap on the mechanical properties of the friction stir spot welding (FSSW) welded AZ series magnesium alloy joints were investigated by microstructural observations, microhardness tests, and tensile tests. The results show that the microstructure of the stir zone adjacent to the periphery of the rotating pin is mainly composed of the upper sheet. The average distance D between the longitudinal segment of the curved interface and the keyhole periphery, the tensile shear force, and the microhardness of the stir zone of the FSSW welded AZ61 alloy joint are the highest in all samples. During FSSW of AZ31 and AZ61 dissimilar magnesium alloys, the irregular deformation of the longitudinal segment of the curved interface appears, while the microhardness of the stir zone is higher when AZ61 alloy is the upper sheet. Moreover, the microhardness of the stir zone increases initially and then decreases sharply in the longitudinal test position.     

铈对AZ31镁合金铸态组织的影响

研究了Ce对AZ31镁合金铸态组织的影响.研究结果表明:添加0.5～1.5 wt%Ce到AZ31镁合金中不但不能细化舍金的晶粒,反而使合金的晶粒变得粗大,并且粗化趋势受Ce加入量的影响较大.当添加0.5 wt%Ce到AZ31镁合金中后,合金的平均晶粒尺寸从最初的60靘增大到164靘.此后,随着Ce加入量从0.5 wt%增加到1.5 wt%,合金的平均晶粒尺寸又开始逐渐减小,但仍大于未添加Ce合金的平均晶粒尺寸.     

Microstructure evolution and mechanical properties of a hot-rolled Ti alloy

The microstructure evolution and mechanical properties of a hot-rolled Ti-5.1 Al-2.5 Cr-0.5 Fe-4.5 Mo-1.1 Sn-1.8 Zr-2.9 Zn titanium alloy sheet along the thickness direction were investigated.The results indicated that the hotrolled titanium alloy sheet presented different microstructures along the thickness direction owing to the uneven distribution of stress and temperature during the hot rolling.The grains in central region underwent a larger deformation,leading to relative complete grain fra...     

复合轧制工艺对Al/Mg复合板冶金结合层组织和性能的影响

采用AZ31镁合金和纯铝进行高温复合轧制制备镁-铝复合板,使其兼具铝的表面耐蚀性和镁合金的高比强度特性.采用金相显微镜、扫描电子显微镜和电子万能拉伸机等设备,研究了不同热轧温度及退火工艺参数对铝-镁复合界面的显微组织和结合强度的影响.结果表明：300 ℃轧制,镁-铝复合板出现严重边裂;450 ℃轧制,边裂消失;在轧制温度为400 ℃、压下率为50%、300 ℃退火2 h的条件下得到的复合板界面结合强度最大,为7.5 MPa.     

焊接电流对镁/镀锌钢 TIG熔--钎焊接头显微组织与力学性能的影响

采用TIG熔-钎焊焊接方法,以镁合金焊丝为填充材料,对镁合金与镀锌钢进行连接实验,并分析热输入量对接头显微组织和力学性能的影响.热输入量过小会阻碍镁/钢界面反应层的形成而使得焊缝难以焊合,热输入量过大又会促进焊缝内部脆性第二相的长大,降低接头力学性能.接头强度随着焊接电流和焊接速度的增大都呈现先上升后下降的趋势,电流为70 A时强度达到最大,该值接近AZ31B母材的88．7%.此时断裂发生于焊缝熔焊区,断面出现大量韧窝和撕裂棱,呈现出塑性断裂特征.     

异步轧制对AZ31镁合金静态再结晶及晶粒细化的影响

研究了AZ31镁合金薄板在异步轧制过程中,异速比、压下率及退火工艺对其退火晶粒尺寸的影响.结果表明:适当提高轧制异速比和道次压下率能够显著细化晶粒,但是异速比过高时,轧辊与轧件会产生相对滑动,细化晶粒效果降低,其中异速比为1.3时,细化晶粒效果最佳;剪切作用使镁合金中孪晶数量及分布均匀程度提高,位错缠结被"切碎",畸变能得以更均匀地分布于变形体内,是异步轧制具有良好晶粒细化效果的主要原因;此外,合理的异步轧制工艺还能缩短镁合金板带所需的中间退火和成品退火时间.     

Si和Sb对AZ31合金铸态显微组织和力学性能的影响

运用光学金相（0M）、扫描电子显微镜（SEM）结合电子拉伸实验研究了0～1．5wt％Si和0—1．5wt％Sb对AZ31合金的显微组织和力学性能的影响。结果表明：Si能够细化AZ31合金组织,但生成的Mg2Si相极易呈现汉字状形貌,降低合金的力学性能11而Sb的加入,可以改善Mg2Si的形貌,同时细化合金显微组织,有助于合金室温力学性能的提高。当AZ31合金加入0．5wt％Si和1．0wt％Sb后,力学性能达到最佳,在保证合金延伸率不变的情况下,抗拉强度达到185MPa,比AZ31合金提高了23．5％．