DEVELOPMENT OF MOLYBDENUM ALLOYS WITH IMPROVED TOUGHNESS BY MECHANICAL ALLOYING

我们通过对纯钼和过渡金属碳化物（TiC或HfC）的混合粉末进行机械合金化和热等静压处理，成功地开发出具有目标性能的钼合金。所开发的合金在低温下表现出大大改善的韧性，大大改善的抗再结晶和晶粒生长，大大改善的抗辐射脆化，并大大改善在高温下的强度比TZM合金，这是目前最广泛使用的钼合金。TEM观察表明，所研制合金在轧制态的组织特征是晶粒尺寸极小（10 ~ 400 nm），位错密度高，晶界处存在大量细小的碳化物颗粒。还已经表明，这样的微观结构对氧杂质的有害影响非常耐受，然而，减少氧的量可以允许进一步改善所开发的合金的性质，这是目前正在进行的。此外，我们正在计划开发具有改善的低温韧性和改善的抗再结晶和辐射脆化的钨合金，因为钨具有金属中最高的熔点，但其使用受到环境温度下晶间脆化的严重影响。

We have successfully developed molybdenum alloys with the aimed properties by applying mechanical alloying and hot isostatic pressing treatment to mixed powders of pure molybdenm and transitional metal carbides (TiC or HfC). The developed alloys exhibit much improved toughness at low temperatures, much improved resistance to recrystallization and grain growth, much improved resistance to radiation embrittlement, and much improved strength at high temperatures than TZM alloy which is currently most widely used among the commerially available molybdenum alloys. TEM observation has showed that the characteristic of microstructures of the developed alloys in the as-rolled state is extremely small grain size ranging from 10 to 400 nm, a high density of dislocations and a large number of very fine carbide particles mostly existing at grain boundaries. It has also been shown that such microstructues are very resistant to the detrimental effect of oxygen impurity, however, reducing the amount of oxygen may allow to further improve the properties of the developed alloys, which is now in progress. In addition, we are planning on developing tungsten alloys having improved low-temperature toughness and improved resistance to recrystallization and radiation embrittlement, because tugsten has the highest melting point among metals, but its use is severely impaired by the intergranular embrittleness at ambient temperature.