摘要
采用光学显微镜研究了Ti-6Al-4V合金经超塑成形/扩散连接(SPF/DB)热影响后的微观组织演变,在室温和空气条件下进行了旋转弯曲疲劳试验,并采用扫描电子显微镜对试样断口形貌进行了观察.结果表明:Ti-6Al-4V合金经历SPF/DB热工艺后,初始的双态组织转变为了等轴组织;强度有所降低,塑性略有提高,而旋转弯曲疲劳极限从420 MPa降低至405 MPa,在相同应力条件下(σ=431 MPa),SPF/DB后试样的疲劳寿命从107量级降低至106量级;疲劳断口源区附近的放射线增粗且变的不连贯,疲劳裂纹扩展区的疲劳条带间距增大,裂纹扩展速率提高.这主要是由于SPF/DB热环境使Ti-6Al-4V合金片层α数量显著减少,降低了晶界总体长度,减弱了α相晶界对疲劳小裂纹扩展的阻碍作用.
The microstructure evolution affected by SPF/DB progress was examined by optical microscopy. The test for rotating bending fatigue limit was carried out at room temperature and in the atmospheric environment. The scanning electron microscopy was used to analyze the rotating bending fatigue fracture. The results indicated that the bimodal microstructure changed into equiaxed microstructure after SPF/DB process. To some extent, the strength decreased with the increase of plasticity, and the rotating bending fatigue limit decreased from the original value 420 MPa to 405 MPa. On the condition that the stress was 431 MPa, the fatigue life decreased from 107 to 106. The radial lines near the crack origin zone changed thicker and discontinuous. The separation between fatigue striations in the crack extension zone changed wider, while the crack propagation rate increased after SPF/DB. This was mainly due to the faction of lamellar α decreased obviously caused by thermal environment which reduced the total length of the grain boundary, and the impediment effect of lamellar α on the crack propagation was also decreased.
出处
《材料科学与工艺》
EI
CAS
CSCD
北大核心
2013年第5期45-50,共6页
Materials Science and Technology
基金
航空基金资助项目(20091125003)
