变形IN718合金冲击断口表面纳米化现象及机制  

Nanostructure at fracture surface of IN718 impact specimen

作　　者：孙文儒[1] 郭守仁[1] 佟百运[1] 卢德忠[1] 胡壮麒[1] 

机构地区：[1]中国科学院金属研究所,沈阳市110016

出　　处：《材料研究学报》2003年第2期122-126,共5页Chinese Journal of Materials Research

基　　金：国家自然科学基金No.59971060和50271072

摘　　要：发现在IN718合金冲击试样断口表面上存在一层极薄的无位错纳米晶层,晶粒尺寸约为20～30nm。在冲击断裂过程中,塑性变形主要集中在裂纹尖端附近的微小区域内。随着裂纹的扩展,沿断口表面形成一极薄的高度塑性变形层,可能是不同方向的位错将其分割成极小的区域。断口表层原子位置的重组释放出高密度的热流导致严重塑性变形层瞬间升温,引发再结晶和纳米晶组织的形成。分析表明,高度塑性变形层愈宽,吸收的冲击功愈多,冲击性能愈好。IN718合金的成分偏析降低高度塑性变形层的宽度和冲击性能。快速加载的冲击性能可能比拉伸等性能对成分偏析更加敏感。A thin layer in which grain size is about 20-30 nm was observed at the fracture surface of IN718 impact specimen. The alloy deforms heavily at the vicinity of the crack tip during fracture, and a deformed heavily thin layer forms at the fracture surface. The readjustment of atoms at the fracture surface heats up the thin layer, causing the recrystallization and formation of a nanostructure. The analysis shows that a wider deformed layer at the fracture surface may absorb more energy and increase the impact toughness. The crack may tend to initiate and propagate along the area heavily precipitated with γ phase due to segregation, causing the decrease of impact toughness. The impact property is more sensitive to segregation relative to tensile properties.

关 键 词：金属材料 表面纳米化 IN718合金 冲击断口 变形 断裂机制 冲击性能 

分 类 号：TG113.25[金属学及工艺—物理冶金]