中文摘要：

研究了应变速率对奥氏体不锈钢Cr17Mn6Ni4cu2N铸坯热塑性的影响。结果表明，壳层的微观组织为6铁索体树枝晶分布在奥氏体晶粒内部，提高应变速率会降低其热塑性，并使裂纹形核位置由6铁素体树枝晶处变为奥氏体晶界处；在芯部铁素体分布在奥氏体晶粒内部及晶界上，提高应变速率会提高其热塑性，且裂纹的形核位置由晶界铁素体处变为晶界铁素体和奥氏体晶界处。在高应变速率下变形，铁素体和奥氏体的强度均提高，并使它们之间的强度差别减小，导致裂纹形核位置由铁素体向奥氏体晶界转移。在壳层，较高的应变速率提高了奥氏体晶界处的应力集中，导致其塑性降低；在芯部，较高的应变速率降低了铁素体处的应力集中，使其热塑性提高。

英文摘要：

The influence of strain rate on the hot ductility of Cr17Mn6Ni4Cu2N has been investigated by hot tensile tests. Results show that： in slab shell, the microstructure is dendrite ferrite distributing in austenite, and reduction of area （RA） decreases as strain rate increasing from 0.1 to 10 s-＇, the positions of cracks nucleus are changed from {5 ferrite dendrites to austenite grain boundary; in slab core, the microstructure is ferrite distributing on austenite grain boundary, and RA increases with strain rate, the positions of cracks nucleus are changed from grain boundary ferrite to the co-existence of grain boundary ferrite and austenite grain boundary. As the materials deform at higher strain rate, the strength can be improved both in austenite and ferrite, which will transfer the cracks nucleating positions from ferrite to austenite grain boundary. In shell the higher strain rate strengthens the stress concentration of austenite grain boundary, leading to the decrease of ductility; in core, the higher strain rate decreases the stress concentration of ferrite, resulting in the increase of ductility.