材料期刊网

本文叙述并讨论了几种固溶处理过的高钼不锈钢在不同温度时效过程中,组织结构变化的情况.16-6Cr-Mo不锈钢在800-1000℃保温,δ-铁素体首先在原来的γ/α相界上形成,然后或者由奥氏体晶粒四周向着中心,或者由晶粒一端向着另外一端推进,最后奥氏体将退缩到晶粒中心或者一个晶粒隅上消失.在600-700℃保温,则发现有层片状铁素体在奥氏体晶粒内形成,然后逐渐增多长大,最后全部代替了奥氏体.在16-6Cr-Mo、16-2.5-6及16-5-6Cr-Ni-Mo不锈钢中,从铁素体内沉淀出来的细小碳化物是一种过渡组织,在x相的成核与长大过程中,它们将不断地进行溶解.16-15-6 Cr-Ni-Mo不锈钢属奥氏体型,在不同温度进行固溶处理,奥氏体都很稳定,在随后的恒温处理过程中,只有碳化物从奥氏体内析出.在这几种钢中碳化物及x相的析出,均能显著地改变钢的硬度.在所研究的两种复相不锈钢中,都观察到有由于x相析出所引起的沉淀硬化现象.

The structural changes in certain quenched ferritic, austenitic and duplex stainless steels during subsequent reheating are described and discussed in detail.In 16-6 Cr-Mo stainless steel, austenite formed at certain solution treatment temperature is metastable and decomposes during subsequent reheating. New ferrite α′ forms at the γ/α interphase boundaries, the rejected carbon atoms then diffuse into the matrix forming alloyed carbides surrounding the γ/α phase boundarries.Fine carbides precipitated from ferrite in 16-6 Cr-Mo, 16-2.5-6 Cr-Ni-Mo, and 16-5-6 Cr-Ni-Mo steels in the early stages of ageing are metastable, during prolonged heating they redissolve and are gradually replaced by χ-phase. Some residual carbides serve as the nuclei of the growing χ-phase. The structure of quenched 16-15-6 Cr-Ni-Mo steel is austenitic, during subsequent heating only M_6C and M_(23)C_6 mixed carbides are precipitated.Both the alloyed carbides and χ-phase may markedly affect the hardness of the steels studied. In the duplex steels χ-phase is a good strengthener, manifesting pronounced hardening effect at elevated temperature.