金属熔体特征温度的分子动力学模拟

发布时间：2018-05-08 05:09

本文选题：分子动力学模拟 + 初始温度　；参考：《西安工业大学》2015年硕士论文

【摘要】：本文采用分子动力学模拟的方法,研究了过热温度和冷却速率对具有fcc结构的A1和具有bcc结构的Fe均质过冷度和凝固组织演化的影响规律。本文主要结论如下：在不同初始温度下,金属Al熔体以1×1011.0K/s的冷速凝固,获得的均质形核过冷度随过热温度的增大而增加,当熔体过热温度达到某一定值后,Al熔体凝固后获得的均质形核过冷度不再随着熔体过热温度的增加而改变,最终模拟获得金属A1的均质形核过冷度达到最大值388 K。金属Fe熔体以1×1011·0K/s的冷速凝固后,获得的均质形核过冷度随着过热温度的增大而逐渐增加,当熔体加热温度达到一定值时,均质形核过冷度不再随着熔体初始温度的增加而改变,模拟得到金属Fe的均质形核过冷度的最大值为847K。将金属Al熔体从1437K以不同冷速冷却至50K并保温弛豫,研究发现,冷速小于1012jK/s时,A1熔体凝固后形成由fcc和hcp镶嵌而成的晶态组织,冷速大于1015·0K/s时,A1熔体凝固后形成非晶态组织,当冷速介于1012·5K/s和1015.0K/s之间时,A1熔体凝固后形成由晶态和非晶态结构所组成的混合组织。模拟获得金属A1熔体形成非晶的临界冷速为1014.5K/s,这与理论计算得出的结果相一致。金属Fe熔体从2169.6K以不同冷速冷却至50K并保温弛豫,研究结果表明,冷速不大于1011.97K/s时,熔体凝固后形成完全由bcc结构组成的晶态组织,当冷速大于1014.8K/s时,熔体凝固后形成完全非晶态组织,当冷速介于1012.0K/s和1014·8K/s之间时,熔体凝固后形成晶态和非晶态的混合结构。分子动力学模拟获得金属Fe熔体形成非晶的临界冷速与理论计算值相吻合。
[Abstract]:The effects of superheating temperature and cooling rate on the evolution of solidified microstructure and homogeneous undercooling degree of Al with fcc structure and Fe with bcc structure were studied by molecular dynamics simulation. The main conclusions of this paper are as follows: at different initial temperatures, the homogeneous nucleation undercooling degree obtained increases with the increase of superheating temperature when Al melts solidify at a cooling rate of 1 脳 1011.0K/s. When the melt overheating temperature reaches a certain value, the homogenized nucleation undercooling degree obtained by solidification of Al melt does not change with the increase of melt superheating temperature. Finally, the maximum homogenous nucleation undercooling degree of Al is obtained by simulation. When Fe melt solidifies at a cooling rate of 1 脳 1011 0K/s, the homogenized nucleation undercooling increases gradually with the increase of superheating temperature. When the melt heating temperature reaches a certain value, the homogenous nucleation undercooling does not change with the increase of the initial melt temperature. The results show that the maximum value of homogeneous nucleation undercooling of Fe is 847K. The melt of Al was cooled from 1437K to 50K at different cooling rate and the heat preservation was relaxed. It was found that when the cooling rate was less than 1012jK/s, the crystalline structure was formed by fcc and hcp after solidification. When the cooling rate was greater than 1015 0K/s, the amorphous structure of Al was formed after solidification. When the cooling rate is between 1012 5K/s and 1015.0K/s, the mixed microstructure composed of crystalline and amorphous structure is formed after solidification. The critical cooling rate of amorphous Al melt is 1014.5 K / s, which is consistent with the theoretical results. Fe melt was cooled from 2169.6K to 50K at different cooling rate and relaxed. The results show that when the cooling rate is not greater than 1011.97K/s, the crystalline structure composed of bcc structure is formed after solidification, and when the cooling rate is higher than 1014.8K/s, the microstructure of the melt is formed. When the cooling rate is between 1012.0K/s and 1014 8K/s, the mixed structure of crystalline state and amorphous state is formed after solidification. The critical cooling rate of amorphous metal Fe melt obtained by molecular dynamics simulation is in good agreement with the theoretical calculation.
【学位授予单位】：西安工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG141;TG146.21

【参考文献】