采用等径转角挤压(ECAP)工艺在室温下对18Ni (C-250)马氏体时效钢进行单道次冷变形.对比固溶处理试样480 ℃时效曲线、固溶+ECAP处理试样的460和480 ℃时效曲线发现,一道次ECAP变形及随后的时效处理能够使马氏体时效钢的峰值时效时间明显缩短,峰值强度提高约100 MPa. 结构分析表明, ECAP态实验钢的马氏体板条宽度为100-200 nm, 随后的时效过程对马氏体板条宽度影响不大, 而ECAP工艺对棒状δ-Ni3Mo相析出尺寸有显著影响. 统计结果表明, 经4 h时效处理后, 固溶+480 ℃时效态、固溶+ECAP+480 ℃, 460 ℃时效态的δ-Ni3Mo宽度(直径)分别为4.92,12.33和3.54 nm. 此外, ECAP工艺还促使18Ni马氏体钢中δ-Ni3Mo相在时效后期加速分解, 使强度迅速衰减.
An 18Ni (C–250) maraging steel was successfully processed by equal–channel angular pressing (ECAP) for a single pass at room temperature. After ECAP deformation, the peak aging time was cut obviously and the peak strength of the steel was enhanced about 100 MPa. Microstructural observations showed that the martensite laths of 18Ni maraging steel were elongated to more narrow bands with a width of 100—200 nm after ECAP deformation, and the width of martensite lath was not affected by the subsequent aging treatment. ECAP deformation has significant influence on the size of rod–shaped δ–Ni3Mo precipitates. It was observed that the widths (diameters) of precipitates in specimens under treatments of solution+480℃, 4 h, solution+ECAP+480℃, 4 h and solution+ECAP+460 ℃, 4 h are 4.92, 12.33 and 3.54 nm, respectively. Additionally, a decomposition of the δ–Ni3Mo precipitates was accelerated after the peak aging time, resulting in a decrease in the strength.
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