Effects of samarium (Sm) content (0, 2.0, 3.5, 5.0, 6.5 wt%) on microstructure and mechanical proper-ties of Mg-0.5Zn-0.5 Zr alloy under as-cast and as-extruded states were thoroughly investigated. Results indicate th...Effects of samarium (Sm) content (0, 2.0, 3.5, 5.0, 6.5 wt%) on microstructure and mechanical proper-ties of Mg-0.5Zn-0.5 Zr alloy under as-cast and as-extruded states were thoroughly investigated. Results indicate that grains of the as-cast alloys are gradually refined as Sm content increases. The dominant intermetallic ph^se changes from Mg3Sm to Mg4iSm5 till Sm content exceeds 5.0 wt%. The dynami-cally precipitated intermetallic phase during hot-extrusion in dll Sm-containing alloys is Mg3Sm. The intermetallic particles induced by Sm addition could act as heterogeneous nucleation sites for dynamic recrystallization during hot extrusion. They promoted dynamic recrystallization via the particle stim-ulated nucleation mechanism, and resulted in weakening the basal texture in the as-extruded alloys. Sm addition can significantly enhance the strength of the as-extruded Mg-0.5Zn-0.5Zr alloy at room temperature, with the optimal dosage of 3.5 wt%. The optimal yield strength (YS) and ultimate tensile strength (UTS) are 368 MPa and 383 MPa, which were enhanced by approximately 23.1% and 20.8% com-pared with the Sm-free alloy, respectively. Based on microstructural analysis, the dominant strengthening mechanisms are revealed to be grain boundary strengthening and dispersion strengthening.展开更多
Effects of La and Nd addition on the microstructure and mechanical properties of the AZ61 alloy have been investigated. The results show that when La and Nd are added into the AZ61 alloy respectively, the β (Mg 17 Al...Effects of La and Nd addition on the microstructure and mechanical properties of the AZ61 alloy have been investigated. The results show that when La and Nd are added into the AZ61 alloy respectively, the β (Mg 17 Al 12 ) phase is refined and granulated, and new phases are formed in the form of small rod like shape, which are verified as La 3 Al 11 and Nd 3Al 11 phase by X ray diffraction and TEM observation. Microstructure observations show that the effective efficiency of La addition is higher than that of Nd addition, thus the sizes of β (Mg 17 Al 12 ) and La 3 Al 11 phase are relatively smaller than those of β (Mg 17 Al 12 ) and Nd 3Al 11 phases in both AZ61 alloy and Nd containing alloy. The increase of the tensile strength and elongation of AZ61 alloy refers to the existence of small rod like La 3 Al 11 and Nd 3Al 11 phases, and fine granulated β (Mg 17 Al 12 ) phase.展开更多
The effects of different contents of Sc addition on the microstructures and properties of the Al 4%Cu alloy were studied by tensile properties measurement, optical microscope, X ray diffraction analysis, scanning elec...The effects of different contents of Sc addition on the microstructures and properties of the Al 4%Cu alloy were studied by tensile properties measurement, optical microscope, X ray diffraction analysis, scanning electron microscope (SEM) and energy spectrum analysis. The experimental results show that rare earth element Sc is capable of refining the dendritic structure of the Al 4%Cu alloy, the tensile strength σ b and yield strength σ 0.2 just increase a little when the content of Sc is lower than 0.2%; when the content reaches 0.3%0.4%, σ b and σ 0.2 slightly decrease; but σ b and σ 0.2 rise again when the Sc content is 0.5%, though both of them are lower than those of the Al 4%Cu alloy without Sc addition. However, Sc addition has little influence on the elongation of the Al 4%Cu alloy. Adding Sc to the Al 4%Cu alloy, when the amount of Sc is lower than 0.2%, Sc mostly exists in the α (Al) solid solution; when the Sc content is in the range of 0.3%0.5%, only a part of Sc exists in the α Al solid solution, the rest appears in two ways: one is that Sc and Al form Al 3Sc which can strengthen the alloy, and the other, Sc interacts with Al and Cu to form AlCuSc phase.展开更多
The Ti-48Al alloy was pack siliconized with 15%Si+85%Al2O3. The microstructure of the siliconized coating on the TiAl-based alloy was analyzed and its effect on oxidation resistance was investigated. The specimens bef...The Ti-48Al alloy was pack siliconized with 15%Si+85%Al2O3. The microstructure of the siliconized coating on the TiAl-based alloy was analyzed and its effect on oxidation resistance was investigated. The specimens before and after cycle oxidation were examined by XRD and SEM equipped with XEDS. The results showed that the coating is composed of a thin Al2O3 outer layer and a composite inner layer of Ti5Si3 with an appropriate amount of Al2O3 dispersed in. Cycle oxidation tests showed that the high temperature oxidation resistance of TiAl-based alloy was greatly improved by forming such composite coating. No spaliation and crack happened and the weight gain was very small after cycle oxidation at 900℃ for 314h.展开更多
基金supported financially by the National Natural Science Foundation of China (Nos. 51701200 and 21601017)the Project for Science & Technology Development of Jilin Province (Nos. 2016YHZ0006, 20170414001GH, 20180520004JH and 20180520160JH)
文摘Effects of samarium (Sm) content (0, 2.0, 3.5, 5.0, 6.5 wt%) on microstructure and mechanical proper-ties of Mg-0.5Zn-0.5 Zr alloy under as-cast and as-extruded states were thoroughly investigated. Results indicate that grains of the as-cast alloys are gradually refined as Sm content increases. The dominant intermetallic ph^se changes from Mg3Sm to Mg4iSm5 till Sm content exceeds 5.0 wt%. The dynami-cally precipitated intermetallic phase during hot-extrusion in dll Sm-containing alloys is Mg3Sm. The intermetallic particles induced by Sm addition could act as heterogeneous nucleation sites for dynamic recrystallization during hot extrusion. They promoted dynamic recrystallization via the particle stim-ulated nucleation mechanism, and resulted in weakening the basal texture in the as-extruded alloys. Sm addition can significantly enhance the strength of the as-extruded Mg-0.5Zn-0.5Zr alloy at room temperature, with the optimal dosage of 3.5 wt%. The optimal yield strength (YS) and ultimate tensile strength (UTS) are 368 MPa and 383 MPa, which were enhanced by approximately 23.1% and 20.8% com-pared with the Sm-free alloy, respectively. Based on microstructural analysis, the dominant strengthening mechanisms are revealed to be grain boundary strengthening and dispersion strengthening.
文摘Effects of La and Nd addition on the microstructure and mechanical properties of the AZ61 alloy have been investigated. The results show that when La and Nd are added into the AZ61 alloy respectively, the β (Mg 17 Al 12 ) phase is refined and granulated, and new phases are formed in the form of small rod like shape, which are verified as La 3 Al 11 and Nd 3Al 11 phase by X ray diffraction and TEM observation. Microstructure observations show that the effective efficiency of La addition is higher than that of Nd addition, thus the sizes of β (Mg 17 Al 12 ) and La 3 Al 11 phase are relatively smaller than those of β (Mg 17 Al 12 ) and Nd 3Al 11 phases in both AZ61 alloy and Nd containing alloy. The increase of the tensile strength and elongation of AZ61 alloy refers to the existence of small rod like La 3 Al 11 and Nd 3Al 11 phases, and fine granulated β (Mg 17 Al 12 ) phase.
文摘The effects of different contents of Sc addition on the microstructures and properties of the Al 4%Cu alloy were studied by tensile properties measurement, optical microscope, X ray diffraction analysis, scanning electron microscope (SEM) and energy spectrum analysis. The experimental results show that rare earth element Sc is capable of refining the dendritic structure of the Al 4%Cu alloy, the tensile strength σ b and yield strength σ 0.2 just increase a little when the content of Sc is lower than 0.2%; when the content reaches 0.3%0.4%, σ b and σ 0.2 slightly decrease; but σ b and σ 0.2 rise again when the Sc content is 0.5%, though both of them are lower than those of the Al 4%Cu alloy without Sc addition. However, Sc addition has little influence on the elongation of the Al 4%Cu alloy. Adding Sc to the Al 4%Cu alloy, when the amount of Sc is lower than 0.2%, Sc mostly exists in the α (Al) solid solution; when the Sc content is in the range of 0.3%0.5%, only a part of Sc exists in the α Al solid solution, the rest appears in two ways: one is that Sc and Al form Al 3Sc which can strengthen the alloy, and the other, Sc interacts with Al and Cu to form AlCuSc phase.
文摘The Ti-48Al alloy was pack siliconized with 15%Si+85%Al2O3. The microstructure of the siliconized coating on the TiAl-based alloy was analyzed and its effect on oxidation resistance was investigated. The specimens before and after cycle oxidation were examined by XRD and SEM equipped with XEDS. The results showed that the coating is composed of a thin Al2O3 outer layer and a composite inner layer of Ti5Si3 with an appropriate amount of Al2O3 dispersed in. Cycle oxidation tests showed that the high temperature oxidation resistance of TiAl-based alloy was greatly improved by forming such composite coating. No spaliation and crack happened and the weight gain was very small after cycle oxidation at 900℃ for 314h.
