Ceramic composites Al_2O_3/(W, Ti)C/Cr_3C_2 with different contents of Cr_3C_2 and (W, Ti)C particles, and with the additive Y_2O_3, were fabricated with hot-pressing technique at 1700 ℃ under 28 MPa pressure for 30 ...Ceramic composites Al_2O_3/(W, Ti)C/Cr_3C_2 with different contents of Cr_3C_2 and (W, Ti)C particles, and with the additive Y_2O_3, were fabricated with hot-pressing technique at 1700 ℃ under 28 MPa pressure for 30 min in N_2 atmosphere. The mechanical properties were tested, and the microstructure was investigated by environment scanning electron microscope (ESEM), transmission electron microscope (TEM), energy dispersive analysis using X-ray (EDAX) and optical microscope (OM). Results indicate that the incorporation of Cr_3C_2 and (W,Ti)C particles can suppress the grain growth of the others, and the toughening and strengthening effects mainly originate from nano-particles, dispersion toughening and solidification strengthening. The multiphase composite ceramic material Al_2O_3/10%Cr_3C_2/20%(W,Ti)C shows good mechanical properties, especially the fracture toughness increases from 4.0 MPa·m 1/2 (Monolithic Al_2O_3 ceramic) to 8.92 MPa·m 1/2, the flexural strength from 260～340 MPa (Monolithic Al_2O_3 ceramic) to 496 MPa, due to incorporation of the suitable contents of Cr_3C_2 and (W,Ti)C particles.展开更多
稀土钢连铸过程中,结晶器内上浮至渣金界面的高熔点稀土夹杂物如果不能被保护渣有效的溶解吸收,进入保护渣后会改变渣的理化性能,影响连铸顺行。通过高温实验研究了CeAlO_(3)在连铸保护渣中的溶解机制,探究了保护渣w(CaO)/w(Al_(2)O_(3...稀土钢连铸过程中,结晶器内上浮至渣金界面的高熔点稀土夹杂物如果不能被保护渣有效的溶解吸收,进入保护渣后会改变渣的理化性能,影响连铸顺行。通过高温实验研究了CeAlO_(3)在连铸保护渣中的溶解机制,探究了保护渣w(CaO)/w(Al_(2)O_(3))(简写为C/A)对溶解过程的影响。实验结果表明,Ce AlO_(3)溶解过程中,夹杂物-渣界面会形成Ce^(3+)和Ca^(2+)的浓度边界层。在C/A为0.8的保护渣中会形成中间产物CaCeAl_(3)O_(7),随着C/A增加到1.0,中间产物Ca Ce Al_(3)O_(7)减少;继续增加C/A至1.2,中间产物消失。其溶解机制为,低C/A渣中AlO_(4)^(5-)较多,在浓度边界层中Ce AOl3溶解形成的Ce^(3+)与渣中Ca^(2+)、Al O45-反应生成中间产物Ca Ce Al_(3)O_(7),然后中间产物再向渣中溶解,溶解方式为间接溶解。高C/A渣中AlO_(4)^(5-)较少,不足以达到固相形核浓度而形成中间产物,Ce AlO_(3)通过离子扩散溶解于渣中。因此,当保护渣C/A低于或等于1,CeAlO_(3)在渣中的溶解方式为间接溶解,当保护渣C/A超过1时,Ce AlO_(3)在渣中的溶解方式转变为直接溶解。展开更多
The CaO–SiO_(2)–Al_(2)O_(3)–MgO system is the main component unit in the slag formation process in blast furnace smelting.Its structural changes directly affect the high-temperature metallurgical properties of slag...The CaO–SiO_(2)–Al_(2)O_(3)–MgO system is the main component unit in the slag formation process in blast furnace smelting.Its structural changes directly affect the high-temperature metallurgical properties of slag.Molecular dynamics simulations were thus conducted to analyze the microstructure changes of the quaternary slag system under different basicities and w(MgO)/w(Al_(2)O_(3))ratios.The changes in w(MgO)/w(Al_(2)O_(3))ratio and basicity could affect the stability of each ion-oxygen.Increasing the basicity and w(MgO)/w(Al_(2)O_(3))ratio,the average coordination number of O surrounding Si atom only changed a little and remained approximately 4,indicating that Si exists as a stable structure of the[SiO4]4−tetrahedron in the slag structure,while the average coordination number of O surrounding Al atom changed greatly from 4 to 6,which indicated that the Al existence form could be transformed from[AlO_(4)]^(5−) tetrahedron to[AlO_(5)]^(7−) pentahedron and[AlO_(6)]^(9−) octahedron.Also,the diffusion rate of ions was accelerated with the increase in w(MgO)/w(Al_(2)O_(3))ratio and basicity.Moreover,the self-diffusion coefficients of each ion were obtained,and the magnitudes were observed to be in the following order:Mg^(2+)>Ca^(2+)>Al^(3+)>Si^(4+).The calculation and analysis of the slag viscosity and activation energy of viscous flow under different basicities and w(MgO)/w(Al_(2)O_(3))ratios revealed that the metallurgical properties of slag at high temperature depend on the flow-unit diffusivity and the microstructure stability,simultaneously,the basicity should be controlled between 1.0 and 1.2,and the w(MgO)/w(Al_(2)O_(3))ratio could be controlled between 0.45 and 0.55.展开更多
文摘Ceramic composites Al_2O_3/(W, Ti)C/Cr_3C_2 with different contents of Cr_3C_2 and (W, Ti)C particles, and with the additive Y_2O_3, were fabricated with hot-pressing technique at 1700 ℃ under 28 MPa pressure for 30 min in N_2 atmosphere. The mechanical properties were tested, and the microstructure was investigated by environment scanning electron microscope (ESEM), transmission electron microscope (TEM), energy dispersive analysis using X-ray (EDAX) and optical microscope (OM). Results indicate that the incorporation of Cr_3C_2 and (W,Ti)C particles can suppress the grain growth of the others, and the toughening and strengthening effects mainly originate from nano-particles, dispersion toughening and solidification strengthening. The multiphase composite ceramic material Al_2O_3/10%Cr_3C_2/20%(W,Ti)C shows good mechanical properties, especially the fracture toughness increases from 4.0 MPa·m 1/2 (Monolithic Al_2O_3 ceramic) to 8.92 MPa·m 1/2, the flexural strength from 260～340 MPa (Monolithic Al_2O_3 ceramic) to 496 MPa, due to incorporation of the suitable contents of Cr_3C_2 and (W,Ti)C particles.
文摘稀土钢连铸过程中,结晶器内上浮至渣金界面的高熔点稀土夹杂物如果不能被保护渣有效的溶解吸收,进入保护渣后会改变渣的理化性能,影响连铸顺行。通过高温实验研究了CeAlO_(3)在连铸保护渣中的溶解机制,探究了保护渣w(CaO)/w(Al_(2)O_(3))(简写为C/A)对溶解过程的影响。实验结果表明,Ce AlO_(3)溶解过程中,夹杂物-渣界面会形成Ce^(3+)和Ca^(2+)的浓度边界层。在C/A为0.8的保护渣中会形成中间产物CaCeAl_(3)O_(7),随着C/A增加到1.0,中间产物Ca Ce Al_(3)O_(7)减少;继续增加C/A至1.2,中间产物消失。其溶解机制为,低C/A渣中AlO_(4)^(5-)较多,在浓度边界层中Ce AOl3溶解形成的Ce^(3+)与渣中Ca^(2+)、Al O45-反应生成中间产物Ca Ce Al_(3)O_(7),然后中间产物再向渣中溶解,溶解方式为间接溶解。高C/A渣中AlO_(4)^(5-)较少,不足以达到固相形核浓度而形成中间产物,Ce AlO_(3)通过离子扩散溶解于渣中。因此,当保护渣C/A低于或等于1,CeAlO_(3)在渣中的溶解方式为间接溶解,当保护渣C/A超过1时,Ce AlO_(3)在渣中的溶解方式转变为直接溶解。
基金The authors received financial support from the National Natural Science Foundation of China(No.51874171)University of Science and Technology Liaoning Talent Project Grants(No.601011507-05)Project of"Xingliao Talents Plan"of Liaoning Province(XLYC1902092).
文摘The CaO–SiO_(2)–Al_(2)O_(3)–MgO system is the main component unit in the slag formation process in blast furnace smelting.Its structural changes directly affect the high-temperature metallurgical properties of slag.Molecular dynamics simulations were thus conducted to analyze the microstructure changes of the quaternary slag system under different basicities and w(MgO)/w(Al_(2)O_(3))ratios.The changes in w(MgO)/w(Al_(2)O_(3))ratio and basicity could affect the stability of each ion-oxygen.Increasing the basicity and w(MgO)/w(Al_(2)O_(3))ratio,the average coordination number of O surrounding Si atom only changed a little and remained approximately 4,indicating that Si exists as a stable structure of the[SiO4]4−tetrahedron in the slag structure,while the average coordination number of O surrounding Al atom changed greatly from 4 to 6,which indicated that the Al existence form could be transformed from[AlO_(4)]^(5−) tetrahedron to[AlO_(5)]^(7−) pentahedron and[AlO_(6)]^(9−) octahedron.Also,the diffusion rate of ions was accelerated with the increase in w(MgO)/w(Al_(2)O_(3))ratio and basicity.Moreover,the self-diffusion coefficients of each ion were obtained,and the magnitudes were observed to be in the following order:Mg^(2+)>Ca^(2+)>Al^(3+)>Si^(4+).The calculation and analysis of the slag viscosity and activation energy of viscous flow under different basicities and w(MgO)/w(Al_(2)O_(3))ratios revealed that the metallurgical properties of slag at high temperature depend on the flow-unit diffusivity and the microstructure stability,simultaneously,the basicity should be controlled between 1.0 and 1.2,and the w(MgO)/w(Al_(2)O_(3))ratio could be controlled between 0.45 and 0.55.
