低频电磁场对7050铝合金铸锭组织的影响

通过在常规半连续铸造过程中施加低频电磁场的方法制备了直径为162mm的7050铝合金铸锭,研究了电磁场对铸锭铸态组织的影响。结果表明,低频电磁场对7050铝合金铸态晶粒尺寸和组织形貌具有显著的影响。施加磁场后铸锭组织变得非常均匀、细小,平均晶粒尺寸由230μm细化至42μm左右,晶粒形貌由粗大枝晶转变等轴晶。电磁场频率和强度对晶粒细化具有重要的影响。对于低频电磁铸造162mm的7050铝合金铸锭,最佳电磁场参数:电磁场频率为25Hz,磁场强度为12800～16000At。     

低频电磁场对半连续铸造Al-Mg-Si-Cu合金显微组织的影响

采用低频电磁场半连续铸造工艺制备Al-Mg-Si-Cu铝合金铸锭,研究了低频电磁场对Al-Mg-Si-Cu铝合金铸锭组织的影响。结果表明,施加低频电磁场可以细化Al-Mg-Si-Cu铝合金铸锭的晶粒组织,减轻晶内元素的偏析程度。与常规半连续铸造相比,施加频率为20 Hz、电流为120 A的交变电磁场后,铸锭中的等轴晶组织增多,枝晶状组织减少,晶粒尺寸变得更加细小,铸锭边部和中心平均晶粒尺寸由常规半连续铸造的170和259μm分别降至133和187μm,同时有利于提高溶质元素在晶内的分布,很大程度上减轻了溶质元素的偏析。此外,低频电磁场的电磁振荡使得液穴内部温度场和流动场更趋均匀,溶质元素分配系数增大,结晶区间变小,抑制了树枝晶的生长,促进了Al-Mg-Si-Cu合金半连续铸锭中非枝晶组织的形成和溶质元素的强制固溶,并且抑制了溶质元素的偏析。     

7A60超高强铝合金的低频电磁铸造(Ⅰ)--直径0.2m锭坯的铸态组织

采用低频电磁铸造技术, 半连续铸造制备了直径为0.2 m的7A60超高强铝合金锭坯. 研究了铸锭表面质量和内裂纹发生情况, 考察了电磁场频率和强度对铸态组织的影响. 结果表明 低频电磁场可消除锭坯裂纹, 改善其表面质量. 在低频电磁场作用下, 半连续铸造组织得到显著细化, 铸锭边部和中间部位的晶粒大小差别减小, 其平均晶粒尺寸分别为30 μm和45 μm. 适当降低电磁场频率和增加强度有利于获得细小均匀的等轴晶组织, 铸造组织最佳的电磁场频率为25 Hz, 安匝数为18 000 A*turn.     

低频电磁热顶铸造7050铝合金铸锭的表面质量和组织

在传统热顶铸造基础上,开发了一种新的热顶铸造结晶器,并在铸造过程中施加低频电磁场;得出了稳定铸造φ500mm 7050高强铝合金铸锭的工艺条件,当电磁场频率为15 Hz、磁场强度为10000 A/m时,铸造出了表面光滑的铸锭.采用偏光显微镜(Leica DMI)观察试样,分析试样的微观组织.试验结果表明:铸造过程中施加低频电磁场能提高铸锭的表面质量,细化铸锭的内部组织,抑制铸锭内部裂纹的产生.总结了低频电磁铸造改善表面质量和细化组织的原因以及低频电磁场对液穴形状的影响.     

低频电磁场参数对Al-10Zn-2.5Mg-2.5Cu-0.15Zr合金铸态组织和性能的影响

采用低频电磁半连续铸造技术，制备了一种新的超高强高韧10Zn-2．5Mg-2．5Cu-0．15Zr铝合金锭坯，考察了电磁场参数频率和强度对铸态组织的影响．结果表明，低频电磁铸造组织均匀、细小、等轴，呈蔷薇形和球形，平均晶粒尺寸为20—40μm；适当增加电磁场频率和安匝数有利于细小均匀的等轴晶组织的获得；最佳的电磁场参数为：电磁场频率为25—35Hz，安匝数为12800—16000AT．相对于常规直接水冷铸造，低频电磁铸造提高铸态拉伸强度极限和延伸率．     

电磁场频率对电磁铸造4045合金微观组织的影响

采用低频电磁半连续铸造技术制备4045铝合金铸坯，比较了常规DC法与低频电磁铸造4045铝合金圆锭(直径为φ100mm)微观组织的形貌。重点考察在10～50Hz范围内，不同的频率使电磁铸造4045铝合金圆锭微观组织发生的变化。结果表明：电磁场频率显著影响合金凝固的微观组织，当频率由50Hz降低到15Hz时，微观组织分布趋于均匀，初晶α-Al晶粒尺寸减小，二次枝晶臂减少，共晶Si形貌由条状变为点状，组织得到明显细化。     

电磁场对2524铝合金扁铸锭微观组织和宏观偏析的影响

采用在常规结晶器上布置线圈而开发的低频电磁半连续铸造技术（LFEC）制备2524铝合金扁铸锭并系统研究其对微观组织和宏观偏析的影响。结果表明,采用低频电磁半连续铸造技术制备的扁铸锭具有更加细小、均匀的铸态组织,而且组织由枝晶和蔷薇型转变为等轴晶组织。低频电磁半连续铸造技术对铸锭宏观偏析具有重要的影响,施加磁场后铸锭中心部分的反偏析明显减弱了。同时,对这些作用的机理进行了探讨。     

低频电磁铸造4045铝合金的微观组织

采用低频电磁半连续铸造技术制备4045铝合金铸坯,比较了常规DC法与低频电磁铸造4045铝合金圆锭(直径100mm)微观组织的形貌。重点考察在15Hz～50Hz范围内,不同的磁场频率对电磁铸造4045铝合金圆锭微观组织的影响。结果表明：电磁场频率的改变可显著影响熔体的凝固组织,频率为30Hz时,其组织最为细小和均匀。     

均匀化处理对低频电磁铸造7050铝合金微观组织的影响

利用低频电磁铸造工艺制备了具有细小、均匀等轴晶组织的7050铝合金铸锭,研究了均匀化处理过程中铸锭微观组织及性能的变化.结果表明,与普通DC铸造锭坯相比,低频电磁铸造铸锭有更佳的均匀化处理效果.在同样的均匀化处理条件下,低频电磁铸造铸锭的晶间低熔点相含量更低,晶内溶质元素含量更高.低频电磁铸造铸锭在均匀化处理12 h后,晶内溶质元素含量即已达到合金的平均含量;而普通铸锭在均匀化处理48 h后,晶内溶质元素含量仍低于合金的平均含量.     

低频电磁铸造超高强铝合金铸锭

通过使用数值模拟和实验相结合的方法,研究低频电磁场对铝合金半连续铸造过程中宏观物理场与铸锭的组织和裂纹的影响;比较低频电磁铸造和DC铸造过程的宏观物理场。结果表明：应用电磁场可以完全改变熔体的流动方向,加快流动速度,均匀熔池内熔体温度,降低温度梯度,提升等温线,减少液穴深度和铸造应力及塑性变形;低频电磁铸造还可以明显细化铸锭的微观组织和消除铸造裂纹,其原因是低频电磁场改变了宏观物理场。     

Direct-chilling casting of Mg alloy under electromagnetic and ultrasonic combined field

The effects of low frequency electromagnetic (LFEC) field and ultrasonic (US) field on the microstructures, macrosegregation of alloying elements and the mechanical properties of DC cast AZ80 alloy were studied. The results show that both LFEC and US fields can refine the grains of the billets, which results in the increase in mechanical properties and uniformity of alloying element distribution. The effective refinement takes place on the edge of ingots when LFEC field is applied, while in the center of billets when field US is adopted. Combined the characteristics of LFEC and US fields, a new process for direct-chilling (DC) casting of Mg-electromagnetic-ultrasonic (ECUS) casting is developed, by which the grains are refined significantly and are more uniform in the whole ingots, and the mechanical properties of the ingots are improved.     

Structure and mechanical properties of AZ31 magnesium alloy billets by different hot-top semi-continuous casting technology

AZ31 alloy billets of 200 mm in diameter were produced by three different processes of conventional direct chill(DC) casting,low-frequency electromagnetic casting(LFEC) and low-frequency electromagnetic vibration casting(LFEVC),respectively.The effect of LFEC and LFEVC on the microstructures,macrosegregation and mechanical properties of AZ31 alloy billets was investigated.In conventional DC casting,the AZ31 alloy billets exhibited coarse grains(about 370 μm) and severe segregation of Al and Zn.In the presence of a solo low-frequency alternating magnetic field or a low-frequency electromagnetic vibration field applied during DC casting of φ200 mm AZ31 billets,grains in the AZ31 alloy billets were effectively refined(about 210 μm) and the macrosegregation of Al and Zn in the billets was greatly decreased.Furthermore,the tensile strength,fracture elongation and hardness of the as-cast AZ31 alloy billets were improved by the processes of LFEC and LFEVC relative to that cast by the process of conventional DC casting.     

物理场对3003/4004复合铸锭凝固组织的影响

采用电磁搅拌、功率超声、超声电磁复合场等不同物理场制备3003/4004铝合金复合铸锭。结果表明,在电磁搅拌作用下,界面附近4004合金一侧α(Al)组织从未施加外场的树枝状转变为花瓣状。在功率超声作用下,4004合金中α(Al)及共晶硅组织都得到了良好的细化。在超声和电磁场联合作用下,界面处4004合金中的α(Al)组织同样得到细化,并且界面处的共晶硅组织较单独超声铸锭的更细小,其形貌从未施加外场时的粗大板条状及施加超声后的细针状转变为细小短棒状。     

Microstructures and constituents of super-high strength aluminum alloy ingots made through LFEC process

Ingots of a new super-high strength Al-Zn-Mg-Cu-Zr alloy were produced respectively by low frequency electromagnetic casting (LFEC) and by conventional direct chill (DC) casting process. Microstructure and constituents of the ingots were studied. The results indicated that the LFEC process significantly refines microstructure and constituents of the alloy, and to some extent, decreases the area (or volume) fraction of constituents and eutectic structure precipitated at grain boundaries. But, no difference in the type of constituents was observed between LFEC and DC ingots. The results also showed LFEC process can improve the as-cast mechanical properties.     

Microstructure and mechanical properties of low frequency electromagnetic casting 7075 aluminum alloy

This work explores the microstructure of low frequency electromagnetic casting (LFEC) 7075 aluminum alloys and investigates the effect of heat treatment process on its mechanical properties via the mechanical properties test, X-ray diffraction and transmission electron microscopy. It was found that the grains of LFEC ingot were finer and more evenly distributed than that of the conventional direct chill cast (DC) ingots. The microstructure of LFEC ingot extruded kept their original as-cast structure with small and fine grains. With the same extrusion ratio, the average grain diameters of LFEC and conventional DC extruded were about 10 and 20 μm, respectively. LFEC extruded also had a better aging property, since the regime of T6 treatment peak value aging was at 120 C for 24 h, the tensile strength and hardness (HV) of the LFEC extruded were 673.50 MPa and 194.62, respectively, which were all higher than those of the conventional DC extruded, indicating that the process regime can be applied in the industrial production.     

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。     

低频电磁铸造Al-4.5%Cu合金微观偏析研究

利用直接水冷半连续(常规DC)铸造工艺和低频电磁铸造(LFEC)工艺分别制备了Al-4.5%Cu(质量分数)合金铸锭. 测量了常规DC铸造和LFEC过程中的温度曲线, 研究了低频电磁场条件下的铸锭微观组织变化和Cu元素的微观偏析. 通过金相观察发现, 在低频电磁场作用下, α-Al和$\theta$相的共晶组织变得细小, 其面积分数明显减小. 利用电子探针测量结果绘制Cu元素成分曲线, 发现在凝固的最初过渡区, Cu元素的成分曲线在低频电磁场作用下升高, α-Al中Cu元素含量增加. 通过计算得到Cu元素的有效分配系数k_e, 发现在最初过渡区k_e线性增大到1. LFEC工艺使得Cu元素的k_e变大, 并且随着电流强度的增强这一趋势愈发明显. 由于低频电磁场加速了凝固前沿的冷却速度, 使更多的Cu原子固溶在 α-Al中, Cu元素在铸锭中的微观偏析得到了改善.