Na-K alloy

例句：

1. 1.The Na-K alloy is used in the production of nuclear reactors.
   钠-钾合金用于生产核反应堆。
2. 2.The Na-K alloy has a high melting point and low density.
   钠-钾合金具有高熔点和低密度。
3. 3. The Na-K alloy was developed to improve the strength of steel.
   钠-钾合金被开发出来以提高钢的强度。