secondary martensite

例句：

1. 1. The material undergoes a transformation from austenite to secondary martensite during the heat treatment process.
   该材料在热处理过程中从奥氏体转变为马氏体。
2. 2. The steel is used in various applications, including automotive and aerospace industries.
   这种钢被用于各种应用，包括汽车和航空航天行业。
3. 3. The secondary martensite phase is responsible for the strength and hardness of the material.
   次级马氏体相是材料强度和硬度的原因。