Special Steel department of Central Iron and Steel Research Institute (CISRI), Beijing, 100081, China.
School of Aeronautics and Astronautics, Sichuan University, Chengdu, 610065, China.
Sci Rep. 2017 Aug 23;7(1):9199. doi: 10.1038/s41598-017-09493-7.
Superplastic materials are capable of exhibiting large tensile elongation at elevated temperature, which is of great industrial significance because it forms the basis of a fabrication method to produce complex shapes. Superplasticity with elongation larger than 500% has been widely realized in many metals and alloys, but seldomly been succeeded in low carbon low alloy steel, even though it is commercially applied in the largest quantity. Here we report ultrahigh superplastic elongation of 900-1200% in the FeMnAl low carbon steels at high strain rate of 10-10 s. Such high-strain-rate superplasticity was attributed to dynamic austenite reverse phase transformation from a heavily cold rolled ferrite to fine-grained ferrite/austenite duplex microstructure and subsequent limited dynamic grain coarsening, under which a large fraction of high angle boundaries can be resulted for superplastic deformation. It is believed that this finding of the low carbon low alloy steel with ultrahigh superplasticity and relative low cost would remarkably promote the application of superplastic forming technique in automobile, aeronautical, astronautical and other fields.
超塑性材料在高温下能够表现出很大的拉伸伸长率，这在工业上具有重要意义，因为它构成了一种制造方法的基础，可以生产出复杂的形状。在许多金属和合金中，已经广泛实现了超过 500%的延伸率的超塑性，但在低碳低合金钢中很少成功，尽管它在商业上的应用数量最大。在这里，我们报告了在高应变速率 10-10 s 下，FeMnAl 低碳钢具有 900-1200%的超高超塑性伸长率。这种高应变速率超塑性归因于从严重冷轧铁素体到细晶粒铁素体/奥氏体双相组织的动态奥氏体反向相变，以及随后的有限的动态晶粒粗化，在此条件下，大量的高角度晶界可以用于超塑性变形。相信这种具有超高超塑性和相对低成本的低碳低合金钢的发现，将极大地促进超塑成形技术在汽车、航空、航天等领域的应用。
