The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put...The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put on the thermodynamic description of the two intermetallic compounds Fe2Ti and FeTi. The C14_Laves phase Fe2Ti was described by the two-sublattice model, which is widely used at present. By checking the homogeneity range on the boundary of the ternary systems involving the binary, the phase boundary of this compound was further confirmed. The FeTi phase with a BCC_B2 crystal structure was treated as the ordered phase of the BCC_A2 phase and a unified Gibbs energy function was used to describe both the ordered and disordered phases. Reproduction of the specific heat capacities of these compounds was another aspect paid particular attention to. Comprehensive comparisons of the calculated and experimental results regarding the phase diagram and thermodynamic properties show a good agreement between them and prove the validity of the present thermodynamic description.展开更多
金铜合金作为金基合金钎焊料在电子工业电真空器件的焊接中发挥关键作用。本文采用真空感应熔炼方法制备金铜合金铸锭,通过冷轧使铸锭发生塑性变形,并结合后续的不同热处理工艺,研究了大变形量（－90%）的金铜合金在不同热处理条件下的...金铜合金作为金基合金钎焊料在电子工业电真空器件的焊接中发挥关键作用。本文采用真空感应熔炼方法制备金铜合金铸锭,通过冷轧使铸锭发生塑性变形,并结合后续的不同热处理工艺,研究了大变形量（－90%）的金铜合金在不同热处理条件下的固态相转变过程;采用光学显微镜（OM）、扫描电镜（SEM）对微观组织进行观察,发现冷变形金铜合金在673－723 K温度范围发生回复,在748－923 K发生再结晶,在923 K以上出现再结晶晶粒长大现象;随后,采用差示扫描量热法（DSC）研究了再结晶组织在连续升温-降温过程中的相转变,即升温过程中发生无序相→Au Cu I→Au Cu II→无序相的转变;而降温过程仅发生了无序相→Au Cu I相的直接转变。利用X射线衍射仪（XRD）发现再结晶组织为金的固熔体结构,而在无序-有序相Au Cu I的转变温度区间,其快淬组织为四方结构的Au Cu I结构;随后,采用高分辨透射电镜（HRTEM）观察证实了此结构,且认为该合金在临界温度以下确实存在有序相的转变。展开更多
Taking experimental path on disordering AuCuI（AAuCu8A4）composed of A Au8 and ACu4 stem alloy genes as an example, three discoveries and a method were presented. The ability of Au Cu I（AAu Cu8 A4）to keep structure ...Taking experimental path on disordering AuCuI（AAuCu8A4）composed of A Au8 and ACu4 stem alloy genes as an example, three discoveries and a method were presented. The ability of Au Cu I（AAu Cu8 A4）to keep structure stabilization against changing temperature is attributed to the fact that the AAu8 and ACu4 potential well depths greatly surpass their vibration energies, which leads to the subequilibrium of experimental path. A new atom movement mechanism of AuCuI（AAuACu84）to change structure for suiting variation in temperature is the resonance activating-synchro alternating of alloy genes, which leads to heterogeneous and successive subequilibrium transitions. There exists jumping order degree, which leads to the existence of jumping Tj-temperature and an unexpected so-called ＂retro-effect＂ about jumping temperature retrograde shift to lower temperatures upon the increasing heating rate. A set of subequilibrium holographic network path charts were obtained by the experimental mixed enthalpy path method.展开更多
基金Project (IP08-092009) supported by Sino Swiss Science and Technology Cooperation (SSSTC)Project (50971136) supported by the National Natural Science Foundation of ChinaProject (1343-71134001013) supported by the Scholarship Award for Excellent Doctoral Student granted by Ministry of Education of China
文摘The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put on the thermodynamic description of the two intermetallic compounds Fe2Ti and FeTi. The C14_Laves phase Fe2Ti was described by the two-sublattice model, which is widely used at present. By checking the homogeneity range on the boundary of the ternary systems involving the binary, the phase boundary of this compound was further confirmed. The FeTi phase with a BCC_B2 crystal structure was treated as the ordered phase of the BCC_A2 phase and a unified Gibbs energy function was used to describe both the ordered and disordered phases. Reproduction of the specific heat capacities of these compounds was another aspect paid particular attention to. Comprehensive comparisons of the calculated and experimental results regarding the phase diagram and thermodynamic properties show a good agreement between them and prove the validity of the present thermodynamic description.
文摘金铜合金作为金基合金钎焊料在电子工业电真空器件的焊接中发挥关键作用。本文采用真空感应熔炼方法制备金铜合金铸锭,通过冷轧使铸锭发生塑性变形,并结合后续的不同热处理工艺,研究了大变形量（－90%）的金铜合金在不同热处理条件下的固态相转变过程;采用光学显微镜（OM）、扫描电镜（SEM）对微观组织进行观察,发现冷变形金铜合金在673－723 K温度范围发生回复,在748－923 K发生再结晶,在923 K以上出现再结晶晶粒长大现象;随后,采用差示扫描量热法（DSC）研究了再结晶组织在连续升温-降温过程中的相转变,即升温过程中发生无序相→Au Cu I→Au Cu II→无序相的转变;而降温过程仅发生了无序相→Au Cu I相的直接转变。利用X射线衍射仪（XRD）发现再结晶组织为金的固熔体结构,而在无序-有序相Au Cu I的转变温度区间,其快淬组织为四方结构的Au Cu I结构;随后,采用高分辨透射电镜（HRTEM）观察证实了此结构,且认为该合金在临界温度以下确实存在有序相的转变。
基金Project(51071181)supported by the National Natural Science Foundation of ChinaProject(2013FJ4043)supported by the Natural Science Foundation of Hunan Province,China
文摘Taking experimental path on disordering AuCuI（AAuCu8A4）composed of A Au8 and ACu4 stem alloy genes as an example, three discoveries and a method were presented. The ability of Au Cu I（AAu Cu8 A4）to keep structure stabilization against changing temperature is attributed to the fact that the AAu8 and ACu4 potential well depths greatly surpass their vibration energies, which leads to the subequilibrium of experimental path. A new atom movement mechanism of AuCuI（AAuACu84）to change structure for suiting variation in temperature is the resonance activating-synchro alternating of alloy genes, which leads to heterogeneous and successive subequilibrium transitions. There exists jumping order degree, which leads to the existence of jumping Tj-temperature and an unexpected so-called ＂retro-effect＂ about jumping temperature retrograde shift to lower temperatures upon the increasing heating rate. A set of subequilibrium holographic network path charts were obtained by the experimental mixed enthalpy path method.
