Verarbeitung hochfester Aluminiumlegierungen durch umformende Verfahren

Forming of high‐strength aluminium alloys A comparison of the forming behavior of both aluminum alloys in as‐received condition (EN AW‐7075 T651) as well as modified condition (EN AW‐7075 ECAP) when processed with conventional forming processes (rolling, extrusion) is conducted on the base of experimentally determined material characteristics. In the following the process limits of the true strain are located by variegating the tool geometry. The influence of the manufacturing method on the plasticity is also a subject matter to analysis. Based upon the outcome of this analysis special tool conceptions are being developed, which allow the forming of highest‐strength aluminum while creating hydrostatical pressure states in the deformed zone. Both simulation and experiments showed material failure of the ultra‐fine‐grained materials when extruded whereas rolling, being the incremental forming process, allowed damage‐free manufacturing of components.     

ECAP变形2J4合金的显微组织和磁性能

研究了等径弯曲通道变形（ECAP）对2J4合金显微组织和磁性能的影响。结果表明，2J4合金在室温下经A方式的ECAP变形后，组织明显细化，原有的奥氏体区部分转变为马氏体，且变形量越大，马氏体的质量分数越多。ECAP变形试样具有比冷轧试样更优异的磁滞性能，表现为更高的矫顽力、剩磁及更大的磁能积。ECAP变形为制备利用率高、成本低的高性能磁性材料提供了一种新途径。     

等径角挤压对Cu-Ni-Be合金时效前后组织和性能的影响

研究了等径角挤(ECAP)处理对Cu-Ni-Be合金时效前后组织和性能的影响.结果表明:挤压8道次后,得到了均匀、细小的蠕虫状最粒,其晶粒尺寸宽为0.5μm左右;等径角挤压后的材料硬度明显升高,挤压8道次后其硬度达198 HB;时效前进行ECAP处理可以加速第二相的析出,明显地提高合金的硬度;经ECAP处理后合金的热稳定性有明显改善.     

基于等径角挤压（ECAP）的超细晶铸造镁合金制备研究

研究了铸造镁合金等径角挤压（ECAP）的原理与技术实施手段.通过设计ECAP模具的几何结构,研究了剪切应变累积效应的度量方法.通过对AM60镁合金铸锭单道次ECAP加工后光学显微组织的观察,讨论了模具几何结构条件（转角与背转角大小）对变形组织演化形态的影响.根据多道次ECAP试验的位移-挤压力关系曲线,考察了加工工艺条件（加工道次数、背压与加工速率）对变形组织形态的影响规律.分析了镁合金ECAP加工技术的试验和模拟方案.研究表明：AM60镁合金铸锭的ECAP变形组织形态较好地符合理论预测结果;多道次ECAP加工显著改善了AM60镁铸锭的微观组织;对于具有粗大晶粒的铸造镁合金而言,ECAP工艺能以机械化冶金方式制备其超细晶结构.     

残余试样对等径角挤压过程的影响

使用DEFORM3D软件，对等径角挤压过程进行有限元模拟，通过对比分析发现，残余试样的存在使挤压需要更大的载荷，使材料应变分布更加均匀，改变了材料的外形，改善了材料在模具内的填充。根据模拟结果，等径角挤压模具设计计算应以存在残余试样的条件为准，并且提出了出口通道的斜角设计。     

等径角挤压工艺对固溶状态CuCrZr合金性能的影响

研究了等径角挤压工艺(ECAP)对固溶态CuCrZr合金性能的影响.结果表明,随着挤压道次的增加,合金的硬度迅速上升,导电率略有下降.时效前经ECAP处理可以加速时效初期第二相的析出,使合金的性能以较快的幅度上升.ECAP六道次试样400℃时效1 h,导电率和硬度分别为81.1%IACS和200 HV30.     

等效应变量对等径角挤压的2A12铝合金力学性能的影响

采用内角为105°、外角为45°及内角为90°、外角为30°两套模具对2A12铝合金进行了等径角挤压实验,研究了等效应变量对其力学性能的影响。结果表明,等径角挤压可以显著改善材料的力学性能,而且等效应变量的大小与材料的力学性能密切相关。经过等径角挤压,材料所经受的累积等效应变量达到4时,材料力学性能的提高达到饱和,而且材料所经受的单次等效剪切应变量越大,材料力学性能的提高越迅速,改善越明显。     

等径角挤压2A12铝合金超细晶组织结构研究

使用Φ=90°和ψ=30°的挤压模具在室温下对2A12铝合金进行了8次等径角挤压,成功制备了晶粒尺寸为200nm左右、具有大角度晶界的块体超细晶材料,并且采用HitachiS-800透射电镜,研究了挤压过程中2A12铝合金的组织结构及其变化。结果表明挤压一次后,晶粒内位错密度急剧增加,形成位错纠缠,晶粒细化效果最明显;挤压前分布在α-Al基体上的针状第二相Al2Cu和颗粒状Al2Cu Mg,在剪切力的作用下,针状Al2Cu变成颗粒状,弥散分布在α-Al基体上,Al2CuMg颗粒因晶粒细化进入了晶界位置,而且在以后的挤压中,这些化合物颗粒大小基本保持不变。继续挤压,位错逐渐由晶内移动到晶界上,在晶界上形成胞状组织,最后逐渐变成了清晰的小角度晶界或大角度晶界,从而实现组织的超细化。     

Microstructure evolution and low temperature superplasticity of ZK40 magnesium alloy subjected to ECAP

Microstructure evolution and superplastic behaviors of ZK40 magnesium alloy were investigated in the temperature range of 473–623 K. Transmission electron microscopy (TEM) was used to study the microstructure changes. After the alloy had been processed by equal channel angular pressing (ECAP) for one pass through the die, significant twinning was found to have occurred, and the mean grain size was 5.6 μm. Finer grains were obtained after multi-pass ECAP, and the average grain size of the alloy ECAPed for three passes was as low as 0.8 μm; this alloy exhibited low temperature superplasticity at 473–523 K, and the elongations obtained at the initial strain rate of 1×10⁻³ s⁻¹ were 260% at 473 K and 612% at 523 K. Corresponding values for the ZK40 alloy processed by ECAP for only one pass were 124% at 473 K and 212% at 523 K. Poor superplastic behavior of the ZK40 alloy processed by ECAP for only one pass was related to the longrange stresses associated with the non-equilibrium grain boundaries within the coarse grains. The incompatibility between the fine grains and the coarse grains was thought to be unfavorable to the improvement of superplascity. This article is based on a presentation in “The 7th Korea-China Workshop on Advanced Materials” organized by the Korea-China Advanced Materials Cooperation Center and the China-Korea Advanced Materials Cooperation Center, held at Ramada Plaza Jeju Hotel, Jeju Island, Korea on August 24–27, 2003.