【作者】 张秋美；

【导师】 李福山；

【作者基本信息】 郑州大学 ， 材料学， 2007， 硕士

【摘要】 探求具有较大玻璃形成能力的热稳定性的合金体系，制备出大尺寸的块体非晶材料一直是研究工作者的目标和夙愿。由于块体非晶合金具有多组元和成分敏感特性目前还没有一个通用的可定量化的判据来确定块体非晶合金的成分区间，只能定性地根据经验规律来探索非晶合金成分，从而使得在大块非晶的尺寸及新体系的发现上，都没有突破性的进展。因此，寻找具有较大玻璃形成能力的非晶合金成分是制备大块非晶的关键。本文从影响非晶形成能力的因素出发，对电子浓度、原子尺寸、混合焓和混合熵等四个因素进行了详细的分析和讨论，得出△H和△S是两个最重要的影响因素。在许多表征非晶形成能力的参数中，只有临界冷却速率与这两个因素都有关系。本文计算了Cu基合金的临界冷却速率，并对计算尺R_c的公式进行了修正，利用修正后的公式计算Cu基和Pd基大块非晶临界冷却速率R_c^*，预测了能形成大块非晶的Cu-Ti-Si和Pd-Cu-Si合金成分范围。论文的主要工作包括以下几个方面：（1）从影响非晶形成能力的电子浓度、原子尺寸、混合焓和混合熵等因素出发，以Zr-Al-Co合金系为例，作线性拟合分析，发现这些因素分别与非晶的热力学参数T_l、T_x、T_g、△H+RT_m和T_g／T_m等成良好的线性关系。（2）全面考虑影响非晶形成能力的电子浓度、原子尺寸、混合焓和混合熵等因素，作多元回归分析，发现可以建立线性模型，通过回归分析对比，可以简化这些模型并且分离出△H和△S这两个最重要的影响因素。（3）通过恰当的处理，可以计算Cu基六元合金系的△G，用△G值计算出Cu基六元合金系的临界冷却速率R_c，并对计算R_c的公式进行了修正，把常数Z修正为Z^*，把用Z^*计算多组元合金系的临界冷却速率记为R_c^*。（4）利用修正后的公式计算Cu基大块非晶临界冷却速率R_c^*，并用R_c^*和T_rg作图对比，用R_c^*和γ作图对比，用R_c^*和D_max作图对比，这些图都显示了用修正后的公式计算出来的R_c^*是可靠的。（5）设Cu-Ti-Si合金系成分为Cu_1-x-yTi_xSi_y，利用修正后的公式计算它们的临界冷却速率R_c^*。（6）形成大块非晶的临界冷却速率为10³K／s，利用修正后的公式预测了能形成大块非晶Cu-Ti-Si合金成分范围。（7）利用修正后的公式计算Pd基大块非晶临界冷却速率R_c^*，并用R_c^*和T_rg作图对比，这个图也都显示了用修正后的公式计算出来的R_c^*是可靠的。（8）设Pd-Cu-Si合金系成分为Pd_1-x-yCu_xSi_y，利用修正后的公式计算它们的临界冷却速率R_c^*。（9）利用修正后的公式预测了能形成大块非晶Pd-Cu-Si合金成分范围。更多还原

【Abstract】 It has been the target and long-cherished wish of researchers to investigate bulk amorphous alloys with high thermal stability and high glass-forming ability and to make the bulk amorphous materials with bigger. Because bulk amorphous alloys have multicomponent and composition sensitivity, so far there is no any single quantificational criterion in general to make certain the composition range of bulk amorphous alloys. So we can quest for the amorphous alloys composition only according to experiential rules. Thus it has no breakthrough headway on the size of the bulk amorphous alloys and the new amorphous systems. Therefore looking for the amorphous alloys composition with bigger glass-forming ability is the key to make the bulk amorphous alloys. The electron density, atom size, mixture enthalpy and mixture entropy were detailedly analysed and discussed. The results indicate that AH and AS are two most important factors. Only the critical cooling rate R_c in many parameters characterizing the glass-forming ability was relevant to the two factors. This paper calculated the critical cooling rate R_c of Cu-based amorphous alloys and modified the expression. It was named as R_c^* which were calculated using the modified expression. The critical cooling rate R_c^* of Cu-based and Pd-based bulk amorphous alloys were calculated. The composition range of the Cu-Ti-Si and Pd-Cu-Si alloys which could form bulk metallic glass were predicted.The main work of this thesis was focused on the following aspects: （1） The electron density, atom size , mixture enthalpy and mixture entropy of the Zr-Al-Co amorphous alloys were discussed by line fitting. The results indicate that these factors are good linearity with the thermodynamics parameters, such as T_l, T_x, T_g,ΔH+RT_m and T_g/T_m. （2） These factors which could fact the glass-forming ability, such as the electron density, atom size , mixture enthalpy and mixture entropy were all taken into accout and made regression analysis. The line models could be build up. By regression analysis contrast these models could be simplified. AH and AS were separated which were two most important factors. （3） By proper disposalΔG in the Cu-based hexahydric alloys could be studied. UsingΔG the R_c of the Cu-based hexahydric alloys could be calculated and modified the expression in which the constant Z was substitute for Z^*. Then this model computed multicomponent alloys could to be named as R_c^*. （4） The critical cooling rate R_c^* of Cu-based bulk amorphous alloys were calculated using the modified expression. The R_c^* with respect to T_rg was shown in Fig. 3.4. The R_c^* with respect toγwas shown in Fig. 3.5. The R_c^* with respect to D（max） was shown in Fig. 3.6. The results show it is feasible to calculate R_c^* using the modified expression. （5） The critical cooling rate R_c^* of Cu-Ti-Si amorphous alloys were calculated using the modified expression. The composition was supposed as Cu_1-x-yTi_xSi_y（at%）. （6） The critical cooling rate is 10³ K/s which could form bulk amorphous alloys. The compositions of Cu-Ti-Si amorphous alloys which could form bulk amorphous alloys were predicted using the modified expression. （7） The critical cooling rate R_c^* of Pd-based bulk amorphous alloys were calculated using the modified expression . The R_c^* with respect to T_rg was shown in Fig. 3.11. The result shows R_c^* is feasible. （8） The critical cooling rate R_c^* of Pd-Cu-Si amorphous alloys were calculated. The composition was supposed as Pd_1-xCu_xSi_y （at%）. （9） The compositions of Pd-Cu-Si amorphous alloys which could form bulk amorphous alloys were predicted using the modified expression .更多还原