Cracks of Cu-Cr-Zr Alloy Bars under Planetary Rolling

摘要:

通过宏观和微观组织研究了棒坯边部、心部的晶粒尺寸及裂纹。利用横断面和纵断面的SEM微观组织分析了心部的裂纹形成机理。结果表明：边部的晶粒因为完成了动态再结晶，使晶粒比心部更加细化；心部约40 μm的微裂纹是由于第二相粒子（体心立方的沉淀相Cr及金属间化合物Cu51Zr14 和Cu5Zr）作为微裂纹的形成源，因为晶粒粗大降低了其强度而诱发。因而细化晶粒能防止微裂纹的形成。裂纹形成机理适合微孔形核、长大和聚合的位错模型。

Abstract:

The paper investigated grain sizes and cracks between the edge and the center of Cu-Cr-Zr alloy bar through macrostructure and microstructure. A crack in the center was explored by images of transverse and longitudinal sections with scanning electron microscope (SEM). Results show that the grain size in the edge is obviously finer than that in the center as completely dynamic recrystallization occurs easily; the microcrack of about 40 μm is formed in the center by second phase particles. Some bcc type precipitates Cr and intermetallics such as Cu51Zr14 and Cu5Zr are the source of microcracks initiation owing to coarse grains decreasing the strength. Therefore, refining of grains in the center is necessary to prevent microcracks. The formation mechanism of cracks can be explained by a dislocation model of microporosity nucleating, growing and polymerizing (MNGP).