用分析电镜、扫描电镜等手段研究了稀土7075铝合金中粗大块状化合物的成分、结构和形成规律。研究表明，在铸态稀土7075合金中出现的粗大块状化合物是一种（Cr，TI）2RE（Al，X）20型稀土化合物，其中X为Mg、Cu、Zn等元素。该化合物具有体心立方结构，晶体常数为1.453～1.458nm，显微硬度为4000～5600MPa，计算密度为3.4g/cm3。合金中（Ti+Cr）含量的减少和凝固时冷却速度的提高均可抑制这种块状化合物的形成。

以流线为边界划分网格，建立了双辊薄带凝固过程的宏观传热模型、溶质传输模型和凝固组织形成的微观模型，并以固相分数为媒介，采用宏观和微观两个不同的时间步长，实现了宏观模型与微观模型的耦合，模拟结果与实际情况吻合较好。

The effects of silicon additions up to 3.5 wt% on the as-cast carbides, as-quenched carbides and as-tempered carbides of high-speed steels W3Mo2Cr4V, W6Mo5Cr4V2 and W9Mo3Cr4V have been investigated. In order to further understand these effects, a Fe-16Mo-0.9C alloy was also studied. The results show that a critical content of silicon exists for the effects of silicon on the types and amount of eutectic carbides in the high-speed steels, which is about 3wt%, 2wt% and 1wt% for W3Mo2Cr4V, W6Mo5Cr4V2 and W9Mo3Cr4V, respectively. When the silicon content exceeds the critical value, the M2C eutectie carbide almost disappears in the tested high-speed steels. Silicon additions were fotmd to raise the precipitate temperature of primary MC carbide in the melt of high-speed steels that contained δ-ferrite, and hence increased the size of primary MC carbide. The precipitate temperature of primary MC carbide in the high-speed steels without δ-ferrite, bowever, was almost not affected by the addition of silicon. It is found that silicon additions increase the amount of undissolved M6C carbide very obviously. The higher the tungsten content in the high speed steels, the more apparent is the effect of silicon additions on the undissolved M6C carbides. The amount of MC and M2C temper precipitates is decreased in the W6Mo5Cr4V and WgMo3Cr4V steels by the addition of silicon, but in the W3Mo2Cr4V steel it rises up to about 2.3wt%.

The thin strip casting of high speed steels W3Mo2Cr4VSi and W6MoSCr4V2 has been investigated. The as-cast strips are of 2.5-4mm thickness, reduced by hot rolling to 1.8-2mm thickness. The steel sheets are used to make power hacksaw blades. The experimental results show that the metallurgical quality of the as-cast strips is now at an acceptable level, and the as-cast carbides in the strips are very free although the eutectic carbide network still exists. However, most of the eutectic carbide network in the strips can be broken up by post-treatment. Cutting test reveals that the performance of these hacksaw blades is satisfactory, compared with that of hacksaw blades made of conventionally produced steel sheets.

Recent research and development status of wrought magnesium alloys in China is reviewed, and more attentions are paid to structure controlling, plastic processing, welding, surface treatment and product application. The control of alloy phases, grain refinement, deforming behavior and twin-roll strip casting process are discussed. The existing problems on the research and development of wrought magnesium alloys in China are analyzed.