Authors: Bin Gou, Ji Ho Gu, Je Hyun Lee, Kwang Jun Euh, Seung Zeon Han
Abstract: The micro-hardness and electric conductivity was studied in as cast alloy Cu-Fe-P alloys which were solution treated at 980°C and aging treated at 400-800°C for 1-20 hours. The micro-hardness peak value was 180 HV and the conductivity peak value was 65% IACS. The hardness and the electric conductivity all depended on precipitation principally. The addition of C in Cu-Fe-P alloy reduced the grain size and accelerated precipitation which resulted in enhancing hardness and electric conductivity together.
267
Authors: Xi Wu Li, Bai Qing Xiong, Yon Gan Zhang, Guo Jun Wang, Zhi Hui Li, Bao Hong Zhu, Feng Wang, Hong Wei Liu
Abstract: In this study, the effect of various aging treatment (T6 and T7 treatment) on the mechanical properties, electrical conductivity and the microstructure of an Al-7.5Zn-1.3Mg-1.4Cu-0.12Zr alloy has been investigated. The results show that with elevating the aging treatment temperatures, the aging response rate is greatly accelerated. When T6 temper is performed at 140°C for 12h, as compared to peak aging for 24h at 120°C, the UTS and the corresponding Elongation values keep the same level, whereas the TYS and the electrical conductivity obviously increase by 5% and 9%, which is up to 560 MPa and 22.6 MS/m, respectively. And there are clear PFZs along the grain boundary and slightly coarser precipitates inside the grain. GPI zones, GPII zones and η' phases are major precipitates for the alloy under T6 condition. When T7 temper is performed on the alloy, the main precipitates are GPII zones, η′ and η phases. The coarser precipitates inside the grain and discontinuous grain boundary precipitates are favorable to electrical conductivity, which decrease the strength of 5~17% compared to T6 treatment. After T76 treatment (i.e., 110°C/6 h + 160°C/6 h), the UTS, TYS, Elongation and electrical conductivity values were 540 MPa, 510 MPa, 16.7% and 23.5 MS/m, respectively.
273
Authors: Yong Xue, Zhi Min Zhang, Li Hui Lang, Li Li
Abstract: In the present paper a research has been made on the effect of aging on the microstructure and mechanical properties of AZ80 and ZK60 wrought magnesium alloys by virtue of optical microscope, electronic scanning microscope and mechanical testers. The research indicates that both the tensile strength and elongation of AZ80 alloy first increase and then decrease as the aging temperature rises, and that, at 140°C-170°C aging temperature, the alloy has good performances in both tensile strength and elongation, they both reaching their peak values at 170°C aging temperature. It has been proved in these researches that while the hardness of ZK60 alloy first increase and then decrease as the aging temperature rises and that the hardness reaches its peak value at 170°C aging temperature, the impact of toughness of the alloy is just the opposite. ZK60 alloy has good performances in both impact toughness and other properties at 140-200°C aging temperature. Constrastive researches have shown that, at the same aging temperature, ZK60 alloy has a better performance than AZ80 alloy.
560
Authors: Gui Qing Wang, Yan Liu, Guo Cheng Ren, Zhong Kui Zhao
Abstract: The correlation of age hardening behavior and Si precipitation in α(Al) of Al-8wt%Si-0.35wt%Mg alloy has been investigated by micro hardness measurement, electron probe microanalysis (EPMA) and transmission electron microscopy (TEM) analysis. The EPMA results show that Si concentration in the center of α (Al) dendrites is higher than that in the edge and the main concentration is about 1.5wt% for Al-8wt%Si-0.35wt%Mg alloy in as cast condition. After solution treatment at 530 °C for 8 h followed by water quenching (T4 treatment), hardness value decreases 9 HV, which is accompanied by the decrease of Si concentration in α (Al). Aging the as-cast sample and T4 treatment sample at 150 °C for 20 h, the main concentration of Mg and Si in α (Al) changes little. Hardness value after as-cast aging is only 3 HV lower than that after T6 treatment. Nanometer Si particles and β″ and/or β′ phases are found in aged samples. The higher hardness value for as-cast aging samples should contribute to the nanometer Si particles in α (Al).
1685
Authors: Prachya Peasura, Bovornchok Poopat
Abstract: The Inconel X-750 indicates good hot corrosion resistance, high stability and strength at high temperatures and for this reason the alloy is used in manufacturing of gas turbine hot components. The objective of this research was study the effect of post weld heat treatment (PWHT) on fusion zone and heat affected zone microstructure and mechanical properties of Inconel X-750 weld. After welding, samples were solutionized at 1500 0C. Various aging temperature and times were studied. The results show that aging temperature and time during PWHT can greatly affect microstructure and hardness in fusion zone and heat affected zone. As high aging temperature was used, the grain size also increased and M23C6 at the grain boundary decreased. This can result in decreased of hardness. Moreover excessive aging temperature can result in increasing MC carbide intensity in parent phase (austenite). It can also be observed that M23C6 at the grain boundary decreased due to high aging temperature. This resulted in decreasing of hardness of weld metal and heat affected zone. Experimental results showed that the aging temperature 705 0C aging time of 24 hours provided smaller grain size, suitable size and intensity of MC carbide resulting in higher hardness both in weld metal and HAZ.
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