In this article, a novel Al-6Zr-2P master alloy with ZrP particles was successfully synthesized, and the refining performance of this novel master alloy for the primary Si in Cu-50Si alloys was also investigated. By m...In this article, a novel Al-6Zr-2P master alloy with ZrP particles was successfully synthesized, and the refining performance of this novel master alloy for the primary Si in Cu-50Si alloys was also investigated. By means of the fracture plane observation, it is found that the ZrP phase would precipitate first in the solidification pro- cess, and then, the ZrAl3 phase grows around them. Fur- thermore, it is observed that the refining effect can be remarkably improved by changing the addition sequence of the raw materials. After the melting of commercial Cu, the 2.0 wt% Al-6Zr-2P master alloy and crystalline Si were added in sequence, and the mean size of the primary Si in Cu-50Si alloy can be significantly refined from 255.7 to 75.3 gm. Meanwhile, the refining mechanism was dis- cussed in detail.展开更多
The effects of Al-P addition on the microstructure and mechanical properties of as-cast Mg–5%Sn–1.25%Si magnesium alloy were investigated. The results show that the phases of the as-cast alloy are composed of α-Mg,...The effects of Al-P addition on the microstructure and mechanical properties of as-cast Mg–5%Sn–1.25%Si magnesium alloy were investigated. The results show that the phases of the as-cast alloy are composed of α-Mg, Mg2 Sn, Mg2 Si, little P, and AlP. The Chinese character shape Mg2 Si phase changes into a granular morphology by P addition because AlP can act as a heterogeneous nucleation core for the Mg2 Si phase. When 0.225wt% of Al–3.5%P alloy is added, the mechanical properties of the Mg–5%Sn–1.25%Si alloy are greatly improved, and the tensile strength increases from 156 to 191 MPa, an increase of 22.4% compared to the alloy without P addition. When the amount of Al–3.5%P reaches 0.300wt%, a segregation phenomenon occurs in the granular Mg2 Si phase, and the tensile strength and hardness decrease though the elongation increases.展开更多
The influence of Nd addition on the glass-forming ability(GFA), microhardness, and corrosion resistance of Mg_(60-x)Cu_(40)Nd_x(x = 5, 10, 15, 20, and 25, at%) alloys were investigated by differential scanning calorim...The influence of Nd addition on the glass-forming ability(GFA), microhardness, and corrosion resistance of Mg_(60-x)Cu_(40)Nd_x(x = 5, 10, 15, 20, and 25, at%) alloys were investigated by differential scanning calorimetry, Vickers-type hardness tests, and electrochemical methods. The results suggest that the GFA and microhardness of the amorphous alloys increase until the Nd content reaches 20at%. The corrosion potential and corrosion current density obtained from the Tafel curves indicate that the Mg_(35)Cu_(40)Nd_(25) ternary alloy exhibits the best corrosion resistance among the investigated alloys. Notably, nanoporous copper(NPC) was synthesized through a single-step dealloying of Mg_(60-x)Cu_(40)Nd_x(x = 5, 10, 15, 20, and 25) ternary alloys in 0.04 mol·L^(-1) H_2SO_4 solution under free corrosion conditions. The influence of dealloying process parameters, such as dealloying time and temperature, on the microstructure of the ribbons was also studied using the surface diffusivity theory. The formation mechanism of dealloyed samples with a multilayered structure was also discussed.展开更多
The SiC gradiently coated carbon fiber/carbon (Cf/C) composites were prepared by a two-step rapid chemical liquid deposition (RCLD) method. The microstructure and properties of the composites were investigated usi...The SiC gradiently coated carbon fiber/carbon (Cf/C) composites were prepared by a two-step rapid chemical liquid deposition (RCLD) method. The microstructure and properties of the composites were investigated using X-ray diffraction, scanning electron microscopy together with energy dispersive X-ray analysis, bending tests, and oxidation tests. The experimental results show that the surface layer of the composites is composed of SiC, pyrocarbon, and carbon fibers. Their inner area consists of pyrocarbon and carbon fibers. The SiC content gradiently decreases with increasing distance from the outer surface to the center of the composites. Furthermore, the thickness of the SiC layer increases with increasing tetraethylorthosilicate content and deposition time. SiC coatings have no significant influence on the bending strength of the composites. However, the oxidation resistance of the composites increases with increasing thickness of the SiC layer.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 51202088)the Shandong Doctoral Foundation (BS2010CL005)+1 种基金the Doctoral Foundation (No. XBS1106)the Research Foundation of the University of Jinan (No. XKY1106)
文摘In this article, a novel Al-6Zr-2P master alloy with ZrP particles was successfully synthesized, and the refining performance of this novel master alloy for the primary Si in Cu-50Si alloys was also investigated. By means of the fracture plane observation, it is found that the ZrP phase would precipitate first in the solidification pro- cess, and then, the ZrAl3 phase grows around them. Fur- thermore, it is observed that the refining effect can be remarkably improved by changing the addition sequence of the raw materials. After the melting of commercial Cu, the 2.0 wt% Al-6Zr-2P master alloy and crystalline Si were added in sequence, and the mean size of the primary Si in Cu-50Si alloy can be significantly refined from 255.7 to 75.3 gm. Meanwhile, the refining mechanism was dis- cussed in detail.
基金financially supported by the National Natural Science Foundation of China (Nos. 50871047 and 51271087)the Natural Science Foundation of Shandong Province, China (No. ZR2010EM071)
文摘The effects of Al-P addition on the microstructure and mechanical properties of as-cast Mg–5%Sn–1.25%Si magnesium alloy were investigated. The results show that the phases of the as-cast alloy are composed of α-Mg, Mg2 Sn, Mg2 Si, little P, and AlP. The Chinese character shape Mg2 Si phase changes into a granular morphology by P addition because AlP can act as a heterogeneous nucleation core for the Mg2 Si phase. When 0.225wt% of Al–3.5%P alloy is added, the mechanical properties of the Mg–5%Sn–1.25%Si alloy are greatly improved, and the tensile strength increases from 156 to 191 MPa, an increase of 22.4% compared to the alloy without P addition. When the amount of Al–3.5%P reaches 0.300wt%, a segregation phenomenon occurs in the granular Mg2 Si phase, and the tensile strength and hardness decrease though the elongation increases.
基金financially supported by the National Natural Science Foundation of China (Nos. 51401085 and 51202088)the Shandong Province Higher Educational Science and Technology Program (No. J14LA06)
文摘The influence of Nd addition on the glass-forming ability(GFA), microhardness, and corrosion resistance of Mg_(60-x)Cu_(40)Nd_x(x = 5, 10, 15, 20, and 25, at%) alloys were investigated by differential scanning calorimetry, Vickers-type hardness tests, and electrochemical methods. The results suggest that the GFA and microhardness of the amorphous alloys increase until the Nd content reaches 20at%. The corrosion potential and corrosion current density obtained from the Tafel curves indicate that the Mg_(35)Cu_(40)Nd_(25) ternary alloy exhibits the best corrosion resistance among the investigated alloys. Notably, nanoporous copper(NPC) was synthesized through a single-step dealloying of Mg_(60-x)Cu_(40)Nd_x(x = 5, 10, 15, 20, and 25) ternary alloys in 0.04 mol·L^(-1) H_2SO_4 solution under free corrosion conditions. The influence of dealloying process parameters, such as dealloying time and temperature, on the microstructure of the ribbons was also studied using the surface diffusivity theory. The formation mechanism of dealloyed samples with a multilayered structure was also discussed.
基金supported by the National Natural Science Foundation of China (No.50371047)
文摘The SiC gradiently coated carbon fiber/carbon (Cf/C) composites were prepared by a two-step rapid chemical liquid deposition (RCLD) method. The microstructure and properties of the composites were investigated using X-ray diffraction, scanning electron microscopy together with energy dispersive X-ray analysis, bending tests, and oxidation tests. The experimental results show that the surface layer of the composites is composed of SiC, pyrocarbon, and carbon fibers. Their inner area consists of pyrocarbon and carbon fibers. The SiC content gradiently decreases with increasing distance from the outer surface to the center of the composites. Furthermore, the thickness of the SiC layer increases with increasing tetraethylorthosilicate content and deposition time. SiC coatings have no significant influence on the bending strength of the composites. However, the oxidation resistance of the composites increases with increasing thickness of the SiC layer.