本文選題：分子動力學(xué)模擬 + 初始溫度��； 參考：《西安工業(yè)大學(xué)》2015年碩士論文

【摘要】：本文采用分子動力學(xué)模擬的方法,研究了過熱溫度和冷卻速率對具有fcc結(jié)構(gòu)的A1和具有bcc結(jié)構(gòu)的Fe均質(zhì)過冷度和凝固組織演化的影響規(guī)律。本文主要結(jié)論如下：在不同初始溫度下,金屬Al熔體以1×1011.0K/s的冷速凝固,獲得的均質(zhì)形核過冷度隨過熱溫度的增大而增加,當(dāng)熔體過熱溫度達(dá)到某一定值后,Al熔體凝固后獲得的均質(zhì)形核過冷度不再隨著熔體過熱溫度的增加而改變,最終模擬獲得金屬A1的均質(zhì)形核過冷度達(dá)到最大值388 K。金屬Fe熔體以1×1011·0K/s的冷速凝固后,獲得的均質(zhì)形核過冷度隨著過熱溫度的增大而逐漸增加,當(dāng)熔體加熱溫度達(dá)到一定值時,均質(zhì)形核過冷度不再隨著熔體初始溫度的增加而改變,模擬得到金屬Fe的均質(zhì)形核過冷度的最大值為847K。將金屬Al熔體從1437K以不同冷速冷卻至50K并保溫弛豫,研究發(fā)現(xiàn),冷速小于1012jK/s時,A1熔體凝固后形成由fcc和hcp鑲嵌而成的晶態(tài)組織,冷速大于1015·0K/s時,A1熔體凝固后形成非晶態(tài)組織,當(dāng)冷速介于1012·5K/s和1015.0K/s之間時,A1熔體凝固后形成由晶態(tài)和非晶態(tài)結(jié)構(gòu)所組成的混合組織。模擬獲得金屬A1熔體形成非晶的臨界冷速為1014.5K/s,這與理論計算得出的結(jié)果相一致。金屬Fe熔體從2169.6K以不同冷速冷卻至50K并保溫弛豫,研究結(jié)果表明,冷速不大于1011.97K/s時,熔體凝固后形成完全由bcc結(jié)構(gòu)組成的晶態(tài)組織,當(dāng)冷速大于1014.8K/s時,熔體凝固后形成完全非晶態(tài)組織,當(dāng)冷速介于1012.0K/s和1014·8K/s之間時,熔體凝固后形成晶態(tài)和非晶態(tài)的混合結(jié)構(gòu)。分子動力學(xué)模擬獲得金屬Fe熔體形成非晶的臨界冷速與理論計算值相吻合。
[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.
【學(xué)位授予單位】：西安工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG141;TG146.21

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本文編號：1860075