Effects of Sc and Mn on microstructures and mechanical properties of Mg-Gd alloy

Two alloys of Mg-12.4Gd and Mg-12.5Gd-0.8Sc-1.4Mn were prepared. Hot extrusion and T5 heat treatment were conducted, and then the mechanical properties of the two alloys were tested at room and high temperatures. The effects of Sc, Mn on the microstructures of Mg-12.4Gd were investigated by optical microscopy, scanning electron microscopy and transmission electron microscopy. The results demonstrate that after hot-extrusion the alloying with Sc, Mn can efficaciously refine the grains of Mg-12.4Gd alloy; and increase the elongation at room and high temperatures after T5 heat treatment. But the strength at high temperature is not obviously improved.     

"挤压-轧制"对Al-Pb合金板材微观结构与力学性能的影响

研究了Al-Pb合金制成板材过程中“挤压-轧制”对板材微观结构与力学性能的影响。结果显示，Al-Pb合金变形前Pb分布在枝晶间隙或“嵌”在基体中；合金热挤压成板材后，合金颗粒内部的Pb细化，但变形颗粒新生表面的Pb粗化，在随后的轧制变形及热处理时难以消除“Pb粗化”造成的遗传影响。合金板材的铝基体发生再结晶前，力学性能主要受Pb形貌影响；发生再结晶后，力学性能主要受基体微观结构影响。     

挤压铸造ZA43合金组织及性能研究

研究了挤压铸造对ＺＡ４３合金组织性能的影响，分析了高压下凝固ＺＡ４３合金的组织形成过程。结果表明：挤压铸造可细化合金的铸态组织、减轻枝晶偏析，大幅度提高其力学性能；枝晶闸显微缩孔的消除是合金韧性显著改善的首要原因。     

AZ31镁合金板材超塑性气胀成形研究

研究了AZ31镁合金板材不同工艺条件下的气胀成形性能。实验表明，胀形高度随温度的升高而增大，且应变速率敏感指数值均大于0.3。在673K,0．7MPa下胀形25min所得的胀形件胀形高度达23．34mm，高径比为0．67。由金相及SEM电镜观察可知，在胀形件的顶端晶界处聚集了大量空洞。通过动态再结晶，晶粒得到了很大细化。并且随变形程度的增大，晶粒细化更明显。AZ31镁合金板材的超塑性胀形主要由晶界滑移控制，动态再结晶则为重要的辅助机制。     

5083铝合金搅拌摩擦焊研究

试验研究了3.5mm厚铝合金5083-H321搅拌摩擦焊工艺,分析了焊接参数对焊缝成型、力学性能和金相组织的影响。结果表明,5083-H321铝合金具有良好的搅拌摩擦焊接性能,采用优化的工艺参数可以使焊接接头的抗拉强度达到母材的93.6%,正弯和背弯角度均可达到180°。     

Effect of the salt addition practice on the grain refining efficiency of Al–Ti–B master alloys

The impact of the salt addition practice on the microstructure and grain refining efficiency of Al–Ti–B alloys produced by the “halide salt” route was investigated. The grain refining performance of an experimental Al–5Ti–1B master alloy was optimized when the halide salts were pre-mixed before addition to aluminium melt at 800 °C during the production of the grain refiner. The stirring action provided during salt addition was found to degrade, while a high rate of addition was found to improve, the grain refining efficiency. In view of the above, an improved salt addition practice to ensure an exceptional grain refining performance is claimed to comprise the following steps: melting commercial purity aluminium ingot; addition of pre-mixed salts to molten aluminium at 800 °C, at once to facilitate a rapid salt reaction, gently mixing the salts with the aluminium melt without introducing any stirring. The grain refiner master alloy thus produced gives an average grain size of 102 μm 2 min after inoculation.     

采用自制简易装置评定高强铝合金的应力腐蚀性能

设计了一种用于铝合金应力腐蚀性能对比的简易快速的实验装置.对7075铝合金和添加1%锂的7075合金在不同热处理状态下的应力腐蚀倾向进行了评定和对比.实验结果表明, 这种简易装置用于应力腐蚀评定,比较好地再现了已知的高强铝合金的应力腐蚀规律.还用这一装置对锂元素和热处理状态对铝合金应力腐蚀的影响进行了研究.     

飞机铝合金型材结构FSW焊接

提出了搅拌摩擦焊接（Friction Stir Welding,FSW）技术的3个基本要素,对铝合金型材FSW焊接件在航空结构中的几个典型应用进行了分析.并简要介绍了中国搅拌摩擦焊中心在铝合金型材搅拌摩擦焊接方面的研究成果.中国搅拌摩擦焊中心的研究表明,采用搅拌摩擦焊技术焊接铝合金能够得到比较满意的接头强度.     

碳化硅晶须增强铝复合材料的断裂研究

在备有拉伸台的扫描电子显微镜上原位观察了V_f为22％的碳化硅晶须增强铝(SiC_W/Al)复合材料压铸态试样和T_6态试样的动态拉伸过程。结果发现外加应力达到180-190MPa时复合材料内部就已形成许多微裂纹,裂纹一般在晶须端部形成,其扩展亦有一定的规律。经过对复合材料简化模型的复变函数分析和计算,求出了晶须周围应力场,进一步通过塑性力学的分析,从理论上解释了本文所观察到的实验现象。     

High temperature corrosion mechanisms and effect of alloying elements for materials used in waste incineration environment

Corrosion products on two typical materials, SA213-T12 steel and alloy 625 exposed to the actual combustion gas, were analyzed in addition to laboratory tests for penetration of corrosive matter. It has been clarified that corrosion products of oxides containing a little chlorides and sulphides show lamellar structures and that at the alloy-scale interface, chlorination, sulphidation, and oxidation occur under a low P_O2-high P_Cl2 condition. The formation of scale structures and the effect of corrosion-resistant alloying elements can be explained according to the stability tendencies of metals, chlorides, and oxides in the M-Cl-O equilibrium diagrams. The severity of corrosion environments at the interface is influenced by the penetration extent of corrosive matters through deposits and scales, and the protective effects of oxide films derived from alloying elements play an important role in preventing the corrosion. On the other hand, it has been shown that thermal fluctuation characterized in this kind of environment makes the lamellar scale structures and sometimes breaks and peels off the scale, and thus accelerates the corrosion. On the basis of the above mentioned knowledge, a new corrosion model is presented.