低活化铁素体-马氏体钢搅拌摩擦焊接头组织和性能分析

Microstructure and mechanical properties of friction stir welded joints of reduced activation ferritic-martensitic steel

关键词:  低活化铁素体–马氏体钢  搅拌摩擦焊  微观组织  力学性能

Key words:  reduced activation ferritic/martensitic steel  friction stir welding  microstructure  mechanical properties

摘要:

文中对9% Cr低活化铁素体-马氏体钢搅拌摩擦焊接头的组织和性能进行了分析.结果表明，搅拌摩擦焊接头不同区域微观组织存在明显的差异.搅拌区内奥氏体的动态再结晶引起晶粒细化和马氏体转变，并且晶界M₂₃C₆相溶解，晶内M₃C相析出；热力影响区组织变化与搅拌区相似，但晶粒尺寸明显大于母材；热影响区和母材区均表现回火组织特征.搅拌区硬度显著提高，分布均匀；热力影响区硬度值变化较大；热影响区发生软化，其硬度值在接头区域最低.随着拉伸测试温度的增加，搅拌区的屈服强度单调降低，抗拉强度先增大后减小，而断后伸长率先减小后增大.

Abstract:

Microstructure and mechanical properties of friction stir welded joints of 9%Cr reduced activation ferritic-martensitic (RAFM) steel were studied in the present paper. The results indicate that there exists significant microstructural difference at different zones in friction stir welded joints. In stir zone (SZ), dynamic recrystallization of austenite leads to grain refinement, martensitic transformation, dissolution of M₂₃C₆ phase and precipitation of M₃C phase. Although microstructure in thermal mechanically affect zone (TMAZ) is similar to SZ, the grain size in TMAZ obviously larger than that in base materials (BM). Both heat affect zone (HAZ) and BM perform tempered microstructural characteristic. The hardness of SZ in joint increases significantly and the distribution is uniform. There is a great variation for hardness in TMAZ. The HAZ is softened and its hardness value is the lowest in the joint. With the increase of the testing temperature, the yield strength decreases monotonically and the ultimate tensile strength first increases and then decreases, while the total elongation decreases first and then increases.