摘要
研究了固溶态0Cr13铁素体不锈钢经室温2道次等径转角挤压(ECAP)及退火处理后的微观结构和力学性能.光学显微镜和透射电镜观察表明,经ECAP挤压变形和650—750℃退火后,样品发生部分再结晶,内部残留约10%—35%(体积分数)均匀分布的岛状超细晶基体.统计表明,再结晶晶粒和超细晶晶粒尺寸呈双峰分布,平均晶粒尺寸分别为5.1—8.3μm和418 525 nm.拉伸和冲击测试结果表明,优选的ECAP挤压变形+700℃退火处理工艺,能够使实验钢获得与常规使用态(锻后700℃退火)相当的冲击韧性(212 J/cm^2),以及比后者更高的屈服强度、均匀塑性和静力韧度(分别提高10%,35%和70%).组织细化和应变硬化能力的提高是造成挤压后退火样品综合力学性能提高的原因.
In comparison with austenitic stainless steel, the ferritic stainless steel has obvious advantage in price due to its lower nickel content. However, the relatively poor ductility and toughness limit its applications. To overcome these shortcomings, a new thermo-mechanical approach, involving processing by severe plastic deformation and proper annealing treatment to introduce a bimodal grain size distribution, was adopted for achieving high work-hardening capability, superior strength-ductility combination and good impact toughness in metallic materials. In this work, the combined effects of severe plastic deformation and partially recrystallization on the microstructures and mechanical properties of a ferritic stainless steel were investigated and compared with the tradi- tional forging and annealing process. An solution^reated ferritic stainless steel （0Crl3, AISI 405） was subjected to equal channel angular pressing （ECAP, an important kind of severe plastic deformation）for two passes at room temperature and subsequent annealing treatments. Optical microscope （OM） and transmission electron microscopy （TEM） observations showed that ultrafine-grained （UFG） struc ture was obtained in the ECAP-processed sample. After subsequent annealing at 650--750 ℃ for 1 h, partial recrystallization occurred and the remaining island-like UFG grains （10%-35% volume fraction） distributed uniformly. Statistical measurements indicated that the microstructures of the annealed ECAP samples exhibited a bimodal grain size distribution including relatively coarse re- crystallized grains （CRGs） and remaining ultrafine grains （UFGs）. The average grain size for CRGs determined from OM observations was 5.1-8.3μm and the average grain size for UFGs measured from TEM observations was 418-525 rim. By contrast, the annealed forged sample （700 ℃） exhibited a uni modal grain size distribution with average grain size of about 74μm. Tensile and impact tests showed that the strength of 0Cr13 ferritic stainless steel could be improved greatly through grain refinement by ECAP process, and the strength-ductility combination could be modulated via sacrificing some strength for ductility by subsequent annealing treatment. In comparison with the conventional sample （forging＋annealing at 700 ℃）, the tested steel processed by the optimal processing involving ECAP deformation and annealing treatment at 700 ℃ showed higher yield strength, uniform ductility and static toughness （enhanced by 10%, 35% and 70% respectively）, simultaneously a comparable impact toughness （212 J/cm2）. The refined microstructure and higher wor^hardening capacity were respon sible for the improved mechanical properties of the annealed ECAP samples and the strengthening mechanisms were discussed based on the experimental results.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2012年第12期1422-1430,共9页
Acta Metallurgica Sinica
基金
国家自然科学基金项目50971045
11172187
中央高校基本科研业务费0212SCU04A05资助~~
作者简介
杨沐鑫，男，1982年生，博士生
