冷变形Au-44%Cu合金固态相转变研究

Solid Phase Transition of Cold-Rolling Au-44%Cu Alloy

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。

The Au-Cu binary alloys used as a kind of Au-based alloy solder play a critical role in the welding of electro-vacuum devices of electronics industry. The Au-Cu alloy ingots were melted and cast by vacuum induction melting,and then treated by cold rolling incorporated with consequent different annealing treatments,and then the solid phase transitions of heavily cold-rolled（ － 90%）Au-Cu alloys were investigated. The recovery,recrystallization and abnormal grain growth of cold deformed Au-Cu alloys were discovered in the range of 673 － 723 K,748 － 923 K and more than 923 K,respectively,through the observation of microstructure evolution via optical microscope（ OM） and scanning electron microscope（ SEM）. The phase transitions of recrystallized structure were studied during the continuous heating and cooling process through differential scanning calorimetry（ DSC） analysis,and the transition of disordered fcc structure→Au Cu I→Au Cu II →A1 took place during heating,whereas the A1 phase transformed into the ordered phase Au Cu I directly during the cooling process. According to the observation of X-ray diffraction（ XRD）,the recrystallized structure was Au solidsolution structure,and the quenched phase obtained in the temperature range of A1 structure→Au Cu I transition was tetragonal structure,which was evidenced by the observation of high resolution transmission electronic microscopy（ HRTEM）,and it was suggested that the ordered phase transition existed indeed below the critical temperature.