双相不锈钢中的相变:金相和磁性质研究

用金相和不同的无损磁试验对商业低合金双相不锈钢及超级双相不锈钢因热处理和冷加工产生的显微结构过程进行了研究。在双相不锈钢(DSS)和超级双相不锈钢(SDSS)中,亚稳态的铁素体由于热处理可以分解为σ相和二次奥氏体相。这些显微结构的改变显著影响着钢材的机械性能、耐腐蚀性能和磁特性。磁性测量使得破坏性实验中获取的谐频和机械性能存在定量关系。在低合金双相不锈钢中,当低含量的Ni被N和Mn取代后,可能导致奥氏体相的不稳定性,奥氏体相容易转变为亚稳态的马氏体相,而SDSS奥氏体会更加稳定。通过室温冷轧(10%～85%压下率)的方法进行固溶退火材料的塑性变形研究,2101材料仅考察了轧制条件,而冷轧2507样本还进行了热处理。冷轧样品用光学显微镜(OM)、扫描电子显微镜(SEM)、X-射线衍射(XRD)和磁试验进行了研究。还对双相不锈钢样品进行了三种不同的磁试验,以确定其磁性能。结果表明冷轧对晶粒的大小和形状有一定影响,磁测试结果还显示2101样品中存在马氏体。

Phase transformations in duplex stainless steels:metallographic and magnetic investigation

Heat treatment and cold working-induced microstructural processes were studied by metallography and different non-destructive magnetic in commercial lean, duplex(DSS) and superduplex stainless steels(SDSS).In DSS and SDSS, the metastable ferrite can decompose to a σ phase and secondary austenite due to heat treatment. All the mechanical, corrosion resistance and magnetic properties are strongly influenced by this microstructural changes. The capabilities of magnetic measurements allow a quantitative correlation between measured harmonics and mechanical properties obtained from destructive tests.In lean duplex, the substitution of Ni by N and Mn in lean grades may result in austenite phase instability, and this phase tends to transform to metastable martensite,while the SDSS auistenite could be more stable.The plastic deformation of the solution annealed materials was carried out by RT cold rolling (10%-85%T.R.). The 2101 was examined only in rolled condition while the cold rolled 2507 samples were also heat treated.The cold rolled samples were examined with OM, SEM, XRD and magnetic measures. Three different magnetic tests were applied for determining the magnetic behaviour of DSS samples. The effect of cold rolling is on grains size and shape and the magnetic tests suggest the martensite presence in 2101.