Rapidly solidified Al-Ti base alloys were prepared by melt spinning at the cooling rate about 107 K/s. The melt-spun ribbons were used to observe the dricrostructures after heat treatment.In the supersaturated Al-Tl-S...Rapidly solidified Al-Ti base alloys were prepared by melt spinning at the cooling rate about 107 K/s. The melt-spun ribbons were used to observe the dricrostructures after heat treatment.In the supersaturated Al-Tl-Si alloy, age hardening occurred after 1 h anneal in the temperature range of 4000~500℃, which seems to be attributed to the precipitation of metastable Ll2- (Al,Si)3Ti phase. However. the microhardness was relatively low because of the low v/o and the insufflcient stability of precipitates. Thus. Cr was added to Al-Ti-Si alloys in order to stabilize the microstructures and to increase the v/o of precipitate5. As a result. the alIoys containing Cr were evaluated to possess the improved properties at the service temperature.展开更多
Rare-earth（RE） element addition can remarkably improve the mechanical properties of magnesium alloys through precipitation hardening. The morphology, distribution and crystal structure of precipitates are regarded a...Rare-earth（RE） element addition can remarkably improve the mechanical properties of magnesium alloys through precipitation hardening. The morphology, distribution and crystal structure of precipitates are regarded as major strengthening mechanisms in the Mg-RE alloys. In order to understand the formation of precipitates during aging at 225 oC in a Mg-10Gd-3Y-0.4Zr alloy（GW103K） with high strength and heat resistance, a high-resolution transmission electron microscopy（HRTEM） was employed to characterize the microstructural evolution. It was found that three types of precipitates were observed in the alloy at the early stage, named as： single layer D019 structure, one single layer D019 structure and one layer of Mg, two parallel single layers（containing RE） and Mg layer in between, which was regarded as ordered segregation of RE, precursors to form β′′ and β′ phase, respectively. Both of β′′ and β′ phase were transformed from the precursors. It was also found that large size of β′ phase and the small size of β′′ phase were constantly existent in the whole aging process. β′ phase played a major role in the strengthening of the GW103 K alloys and the decrease of the hardness was caused by the coarsening of β′ phase.展开更多
文摘Rapidly solidified Al-Ti base alloys were prepared by melt spinning at the cooling rate about 107 K/s. The melt-spun ribbons were used to observe the dricrostructures after heat treatment.In the supersaturated Al-Tl-Si alloy, age hardening occurred after 1 h anneal in the temperature range of 4000~500℃, which seems to be attributed to the precipitation of metastable Ll2- (Al,Si)3Ti phase. However. the microhardness was relatively low because of the low v/o and the insufflcient stability of precipitates. Thus. Cr was added to Al-Ti-Si alloys in order to stabilize the microstructures and to increase the v/o of precipitate5. As a result. the alIoys containing Cr were evaluated to possess the improved properties at the service temperature.
基金Project supported by the National Natural Science Foundation of China(51171113,51301107 and 51474149)China Postdoctoral Science Foundation(2012M511089,2013T60444)
文摘Rare-earth（RE） element addition can remarkably improve the mechanical properties of magnesium alloys through precipitation hardening. The morphology, distribution and crystal structure of precipitates are regarded as major strengthening mechanisms in the Mg-RE alloys. In order to understand the formation of precipitates during aging at 225 oC in a Mg-10Gd-3Y-0.4Zr alloy（GW103K） with high strength and heat resistance, a high-resolution transmission electron microscopy（HRTEM） was employed to characterize the microstructural evolution. It was found that three types of precipitates were observed in the alloy at the early stage, named as： single layer D019 structure, one single layer D019 structure and one layer of Mg, two parallel single layers（containing RE） and Mg layer in between, which was regarded as ordered segregation of RE, precursors to form β′′ and β′ phase, respectively. Both of β′′ and β′ phase were transformed from the precursors. It was also found that large size of β′ phase and the small size of β′′ phase were constantly existent in the whole aging process. β′ phase played a major role in the strengthening of the GW103 K alloys and the decrease of the hardness was caused by the coarsening of β′ phase.
