Papers by Keyword: Creep Rupture Life

Abstract: The P92 steels were aged at 632°C for 500hrs and 1,000hrs, and creep ruptured at 650°C~625°C with stress of 120~110 MPa. The creep rupture life (CRL) of the aged samples was decreased with the aged time. The microstructure of the P92 steel was observed as fine tempered lath with dispersion of Cr-rich M₂₃C₆ along various grain boundaries. Upon aging and creep, recovery of lath and precipitation of coarse W-rich Laves phase were characterized as the main microstructural change. The M₂₃C₆ is relatively stable upon the short-term aging and creep. Decrease of the CRL of the aged specimens is considered as the degradations of microstructure such as the recovery of lath due to the dislocation annihilation and precipitation of coarse Laves phase.

Abstract: The effect of V content on the mechanical properties and microstructure of DZ417G alloy was studied in the present investigation. DZ417G alloy with different element V contents was smelted , then tested the mechanical properties and observed microstructure. The results show that with the increase of element V content, the morphology of rod type M₂₃C₆ carbides turned into block-type MC carbides, the size of carbides became bigger, and the amount of carbides decrased, but the dispersion degree of carbide in the matrix was increased. The alloy tensile strength and plastic properties were increased at high temperature with the increment of V content. There were finer dimple structures on the tensile rupture fracture surface of the alloy with high element V than the alloy with low element V under the high temperature conditions. The results of creep rupture life tests show that with increasing V content the creep rupture life increased at the test condition of 760 °C, 725MPa. The creep rupture life is 90h of the alloy with 0.62% V element content, and the creep rupture life increased to more than 245h when the element V content increased to 0.96%.

Abstract: Creep property is one of the most important factors to affect the reliability of soldered joints. The effect of rare earth(RE) on the creep rupture life of Sn2.5Ag0.7Cu solder joints were investigated under constant temperature and stress using creep specimens with a 1mm² cross sectional area. The results show that adding tiny RE in Sn2.5Ag0.7Cu solder alloy can effectually affect the size and configuration of the intermetallic compound (IMC) of interfacial layer. The IMC of Sn2.5Ag0.7Cu interfacial layer is thinner and its thickness is homogeneous with adding 0.1% RE, and the creep rupture life of solder joints is longest, which is apparently superior to that of Sn2.5Ag0.7Cu and commercial used Sn3.8Ag0.7Cu solder alloy.

Abstract: The effects of Ni on the properties of the Sn-2.5Ag-0.7Cu-0.1Re solder alloy and its creep properties of solder joints are researched. The results show that with adding 0.05wt% Ni in the Sn-2.5Ag-0.7Cu-0.1Re solder alloy, the elongation can be sharply improved without decreasing its tensile strength and it is 1.4 times higher than that of the commercial Sn-3.8Ag-0.7Cu solder alloy. Accordingly the creep rupture life of Sn-2.5Ag-0.7Cu-0.1Re-0.05Ni solder joints is the longest, which is 13.3 times longer than that of Sn-2.5Ag-0.7Cu-0.1Re and is also longer than that of the commercial Sn-3.8Ag-0.7Cu solder alloy. In the same environmental conditions, the creep rupture life of Sn-2.5Ag-0.7Cu-0.1Re-0.05Ni solder joints can sharply decrease with increasing the temperature and stress.

Abstract: Particle-enhanced is the way to improve properties of solder alloys. In the present work, the influence of Ag particle-enhanced on the wettability and creep rupture life of 99.3Sn0.7Cu eutectic solder with Ag content of 1vol% to 10vol% were investigated. It was indicated that the wettability of the composite solders could be improved by adding minute amount of Ag particles. With increasing the amount of Ag particles, the spreading areas of the composite solders increased when Ag was below 5vol%. When Ag was above 5vol%, the spreading areas started decreasing. When Ag content was up to 10vol%, the wettability of the composite solder sharply deteriorated. In addition, the creep rupture lives of the composite solders were longer than that of 99.3Sn0.7Cu eutectic solder at the same condition. When Ag content was 5vol%, the creep rupture life of the composite solder was the longest among the investigated composite solders and about 23 times of that of 99.3Sn0.7Cu eutectic solder.

Abstract: X20CrMoV12 1 steels were exposed at three different high temperatures and various durations. Aging parameter, LMP _s, was used to describe long-term thermal history. Creep rupture, hardness and tensile tests for aged X20CrMoV12 1 steels were carried out. Yield strength was slightly decreased and hardness was rapidly decreased afterLMP _s reached 20.6. Creep strength of aged X20CrMoV12 1 steel decreased rapidly after the LMP_s reached 20.6. It was shown that the creep strength decreased due to the coarsening of acicular type M₂₃C₆ at subgrain boundaries and the agglomeration of M₂₃C₆ at prior austenite grain boundaries. After LMP_s reached 20.6, the assumed linear regression line of stress and Larson-Miller parameter,LMP_f, also moved toward a lower LMP_f region as aging parameter increased. The dependency of creep rupture life on the microstructural degradation could be represented by C_LMPs, which is LMP_f at stress of 1 kg/mm². It was found that the creep rupture life of X20CrMoV12 1 steel could be predicted by considering the material degradation during and prior to creep test.