This study is focused on the effect of boron addition, in the range of 0.0007wt% to 0.03wt%, on the microstructure and stress-rupture properties of a directionally solidified superalloy. With increasing boron content ...This study is focused on the effect of boron addition, in the range of 0.0007wt% to 0.03wt%, on the microstructure and stress-rupture properties of a directionally solidified superalloy. With increasing boron content in the as-cast alloys, there is an increase in the fraction of the γ′/γ eutectic and block borides precipitate around the γ′/γ eutectic. At a high boron content of 0.03wt%, there is precipitation of lamellar borides. Upon heat treatment, fine block borides tend to precipitate at grain boundaries with increasing boron content. Overall, the rupture life of the directionally solidified superalloy is significantly improved with the addition of nominal content of boron. However, the rupture life decreases when the boron content exceeds 0.03wt%.展开更多
It is generally agreed that appropriate content of boron is beneficial to mechanical properties of many superalloys. In an effort to improve stress rupture properties of a new superalloy M951, the content of boron is ...It is generally agreed that appropriate content of boron is beneficial to mechanical properties of many superalloys. In an effort to improve stress rupture properties of a new superalloy M951, the content of boron is optimized. Stress rupture tests were carried out using a FC-20 high temperature creep testing machine. The micro- structure, fracture surface and dislocation structure were investigated by optical microscopy, scanning electron microscopy and transmitting electron microscopy. The results indicate that the addition of boron improves the stress-rupture life at 1100℃ and 40MPa, but does not affect elongation remarkably. The stress-rupture life is the longest when the content of boron is 0.024%. Boron also enhances the tensile ductility and has no obvious effect on the tensile strength.展开更多
This paper investigates the procedure of cubic boron nitride （cBN） thin film delamination by Fourier-transform infrared （IR） spectroscopy. It finds that the apparent IR absorption peak area near 1380cm^-1 and 1073...This paper investigates the procedure of cubic boron nitride （cBN） thin film delamination by Fourier-transform infrared （IR） spectroscopy. It finds that the apparent IR absorption peak area near 1380cm^-1 and 1073 cm^-1 attributed to the B-N stretching vibration of sp2-bonded BN and the transverse optical phonon of cBN, respectively, increased up to 195% and 175% of the original peak area after film delamination induced compressive stress relaxation. The increase of IR absorption of sp2-bonded BN is found to be non-linear and hysteretic to film delamination, which suggests that the relaxation of the turbostratic BN （tBN） layer from the compressed condition is also hysteretic to film delamination. Moreover, cross-sectional transmission electron microscopic observations revealed that cBN film delamination is possible from near the aBN（amorphous BN）/tBN interface at least for films prepared by plasma-enhanced chemical vapour deposition.展开更多
文摘This study is focused on the effect of boron addition, in the range of 0.0007wt% to 0.03wt%, on the microstructure and stress-rupture properties of a directionally solidified superalloy. With increasing boron content in the as-cast alloys, there is an increase in the fraction of the γ′/γ eutectic and block borides precipitate around the γ′/γ eutectic. At a high boron content of 0.03wt%, there is precipitation of lamellar borides. Upon heat treatment, fine block borides tend to precipitate at grain boundaries with increasing boron content. Overall, the rupture life of the directionally solidified superalloy is significantly improved with the addition of nominal content of boron. However, the rupture life decreases when the boron content exceeds 0.03wt%.
文摘It is generally agreed that appropriate content of boron is beneficial to mechanical properties of many superalloys. In an effort to improve stress rupture properties of a new superalloy M951, the content of boron is optimized. Stress rupture tests were carried out using a FC-20 high temperature creep testing machine. The micro- structure, fracture surface and dislocation structure were investigated by optical microscopy, scanning electron microscopy and transmitting electron microscopy. The results indicate that the addition of boron improves the stress-rupture life at 1100℃ and 40MPa, but does not affect elongation remarkably. The stress-rupture life is the longest when the content of boron is 0.024%. Boron also enhances the tensile ductility and has no obvious effect on the tensile strength.
基金supported by the National Science Foundation of Zhejiang Province,China (Grant No Y405051)the Zhejiang Provincial Education Department,China (Grant No 20061365)the Education Ministry Scientific Research Startup Foundation for Returnee,China (Grant No 2007-24)
文摘This paper investigates the procedure of cubic boron nitride （cBN） thin film delamination by Fourier-transform infrared （IR） spectroscopy. It finds that the apparent IR absorption peak area near 1380cm^-1 and 1073 cm^-1 attributed to the B-N stretching vibration of sp2-bonded BN and the transverse optical phonon of cBN, respectively, increased up to 195% and 175% of the original peak area after film delamination induced compressive stress relaxation. The increase of IR absorption of sp2-bonded BN is found to be non-linear and hysteretic to film delamination, which suggests that the relaxation of the turbostratic BN （tBN） layer from the compressed condition is also hysteretic to film delamination. Moreover, cross-sectional transmission electron microscopic observations revealed that cBN film delamination is possible from near the aBN（amorphous BN）/tBN interface at least for films prepared by plasma-enhanced chemical vapour deposition.
