Suhua AI
,
Zhongguang WANG
,
Yun ZHANG and Zhuangqi HU(State Key Laboratory for Fatigue and Fracture of Materials
,
Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang 110015
,
China)
材料科学技术（英）
Fatigue lives for the smooth and notched specimens of 8090 Al-Li alloy jn the different ageing conditions have been studied. For the smooth samples of 8090 alloy the artificial ageing results in an increase in fatigue life in comparison with natural ageing. On the contrary, the notched specimens of 8090 alloy in the naturally aged condition show higher fatigue life than in the peak-aged. The exposure to either the peak-aged or naturally aged leads to superior fatigue properties of Al-Li alloy to the traditional high strength aluminum alloys of 7075 and 2024, especially in the latter aged condition. In all ageing conditions, i,e. naturally, under-, peak- and over-aged, the peak-aged 8090 alloy displays the highest fatigue life and the over-aged material has a minimum value at the same stress amplitude. The difference in fatigue life is mainly attributable to the size and distribution of strengthening precipitates as well as the wide of precipitate free zones (PFZ's) along grain boundaries.
关键词:
Fuhe YUAN
,
Zhiwei HUANG
,
Zhongguang WANG
,
Chao SUN
,
Shijie ZHU
材料科学技术（英）
Detonation spraying has advantages of strong bonding without heating substrates, high coating speed, low requirements for the quality of surface treatment of substrates and others. In the present research, yttria stabilized zirconia powders were used for detonation spraying thermal barrier coatings (TBCs) on a Ni-base superalloy with a bond coat of NiCrAlY. Thermal exposure tests were conducted at a constant temperature in air. After thermal exposure, microstructure observation, element distribution analysis and hardness measurement were carried out. The cracking behavior of the as-prepared and preoxidized TBCs specimens was investigated.
关键词:
Detonation spraying
,
null
,
null
,
null
Hui ZHANG
,
Yuechen WANG
,
Feng LIU
,
Suhua AI
,
Qishan ZANG
,
Zhongguang WANG
材料科学技术（英）
In-phase (IP) and out-of-phase (OP) thermal-mechanical fatigue (TMF) behavior of cast Ni-base superalloy K417 was studied. All experiments were carried out under total strain control with temperature cycling between 400~850℃. Both in-phase and out-of-phase TMF specimens exhibited cyclic hardening followed by cyclic softening at the minimum temperature. Besides, they cyclically hardened in the early stage of life followed by cyclic softening at the maximum temperature. OP TMF life was longer than that of IP TMF. Various damage mechanisms operating in different controlled strain ranges and phasing were discussed. A few life prediction methods for isothermal fatigue were used to handle TMF fatigue and their applicability to superalloy K417 was evaluated. The SEM analysis of the fracture surface showed that transgranular fracture was the principal cracking mode for both IP and OP TMF. Oxidation was the main damage mechanism in causing shorter fatigue life for IP TMF compared with OP TMF.
关键词:
Thermal-Mechanical fatigue
,
null
