Duplex Stainless Steels (DSSs) are biphasic austenite-ferrite stainless steels, with higher mechanical properties and corrosion resistance than the other stainless steels grades. Impact toughness is a very important mechanical property and even though DSSs have a lower impact toughness as compared to the austenitic grades, the transition to ductile to brittle behavior is more gradual and it occurs at lower temperature than ferritic grades. On the other hand, DSSs suffer from embrittlement due to secondary phase precipitation, which affects all mechanical and corrosion properties, in particular impact toughness, even in low amount.

In this research paper, the influence of a small amount (< 2%) and different morphologies of secondary phases (coarse and finely dispersed) on the ductile to brittle transition of standard Duplex Stainless Steel UNS S32205 was studied. Two isothermal heat treatments were conducted on the solubilized DSS in order to precipitate the same amount but different morphologies of secondary phases. Charpy tests were conducted on a temperature range between 20 °C and − 196 °C.

The wrought material retained a very good impact toughness even at − 90 °C (100 J), but a small volume fraction of secondary phases affected the impact toughness even at room temperature. Coarser secondary phases affect the impact toughness largely as compared to small and finely dispersed particles.

双相不锈钢（DSS）是双相奥氏体-铁素体不锈钢，具有比其他不锈钢更高的机械性能和耐腐蚀性。冲击韧性是非常重要的机械性能，尽管与奥氏体钢种相比，DSS的冲击韧性较低，但从韧性到脆性的过渡更为平缓，并且其发生温度低于铁素体钢种。另一方面，DSS由于二次相沉淀而脆化，即使少量也影响所有的机械和腐蚀性能，特别是冲击韧性。

在本文中，研究了少量（<2％）和不同的次级相形态（粗大和细分散）对标准双相不锈钢UNS S32205的韧性至脆性转变的影响。为了溶解相同数量但不同形态的次级相，对溶解的DSS进行了两次等温热处理。夏比测试在20°C至− 196°C的温度范围内进行。

锻造材料即使在− 90°C（100 J）时也保持了很好的冲击韧性，但是即使在室温下，次生相的体积分数也很小，影响了冲击韧性。与较小且细分散的颗粒相比，较粗的次级相对冲击韧性的影响很大。