Aging Behavior Of Cu-Cr-Zr Copper Alloy With High Strength And High Conductivity

With the rapid development of electronic industry,Cu-Cr-Zr alloy has been widely concerned because of its high strength and good electrical conductivity.However,the opinion of experts and scholars on the aging behavior study of Cu-Cr-Zr system are different,especially the precipitated phase species and size distribution.The single aging,double aging,cryogenic treatment and aging heat treatment process of high strength and high conductivity Cu-Cr-Zr copper alloy was studied in this paper,and Mg and Si alloying effect on various aging heat treatment process of the alloy was also explored in this paper.The high strength and high conductivity Cu-Cr-Zr alloy aging kinetics equation was established based on conductivity analysis.The mechanism of Mg and Si alloying,and cryogenic pretreatment effect on kinetics of isothermal aging were both analysed.The results of the study show that:(1)Mg and Si elements can improve the strength and conductivity of Cu-Cr-Zr high strength and high conductivity copper alloys.The best aging process of Cu-Cr-Zr alloy is 410? for ageing 8h based on orthogonal experiment.At this time,the strength of the alloy is 570MPa,and the electrical conductivity is 79.1%IACS.The best aging process of Cu-Cr-Zr-Mg-Si alloy 430? for ageing 14h.At this time,the strength of the alloy is 595MPa,the electrical conductivity is 80.4%IACS.The optimum aging temperature of Cu-Cr-Zr alloy is improved by Mg and Si composite micro alloying,and the heat preservation time is prolonged.Cu-Cr-Zr alloy is selected by selective electron diffraction and XRD phase retrieval as Cr and Cu5Zr.The Cr phase is about 100-200nm and the Cu5Zr phase is about 50-100nm.The precipitation phase of Cu-Cr-Zr-Mg-Si alloy after aging is also Cr and Cu5Zr.The precipitates are finer,and the distribution is more uniform.Cr phase size is also 50-100nm,but the size of Cu5Zr phase decreases significantly,its size is about 50nm.(2)The optimal double stage aging combination of Cu-Cr-Zralloy is 270? for 1h +410? for 4h.At this point,the strength of Cu-Cr-Zr alloy is 580MPa,the conductivity is 76.9%IACS.The optimal double stage aging combination of Cu-Cr-Zr-Mg-Si alloy is 290?for 1h + 430? for 6h.At this point,the strength of Cu-Cr-Zr-Mg-Si alloy is 615MPa,and the conductivity is 79.3%IACS.Low temperature pre aging can obtain high dispersed GP area,providing more nucleation sites for the second aging,double aging can obtain more dispersed phase compared with single aging.(3)Optimum parameters of Cu-Cr-Zr alloy cryogenic treatment + aging treatment is 10 times cryogenic treatment of +390? ageing for 8h,the strength of the alloy is 585MPa,the conductivity is 78.9%IACS.Optimum parameters of Cu-Cr-Zr-Mg-Si alloy cryogenic treatment + aging treatment is 15 times cryogenic treatment + 410?aging 12h.At this time,the strength of the alloy is 605MPa,conductivity is79.2%.TEM microstructure show that cryogenic treatment makes the alloy internal more dislocations,providing more nucleation sites for the aging process and getting more dispersed phase precipitation.(4)Differential scanning calorimetry(DSC)on the dynamic aging kinetics of Cu-Cr-Zr alloy were studied.The dynamic equations of the aging temperature:t=(T-298)/[T2exp(-1193/T-6.3)]..Cu-Cr-Zr alloy isothermal aging kinetics equation based on the phase transformation kinetics of conductivity change,450? ageingdynamic equation of phase transformation:?=1-exp(-1.82t0.84),430? ageing dynamic equation of phase transformation:? = 1-exp(-1.65t0.74),410?ageing dynamic equation of phase transformation:?=l-exp(-1.31t0.74),390 ?ageing dynamic equation of phase transformation:?=1-exp(-1.23t0.88).The temperature aging kinetics equation can be compared with the isothermal aging kinetics equation.(5)Mg,Si micro alloying elements and cryogenic pretreatment effect on isothermal aging kinetics of Cu-Cr-Zr alloy can be characterized by the TTT curve.The micro alloying elements Mg and Si can make the TTT curve of Cu-Cr-Zr alloy move right,increased incubation time.The alloy is not easy to produce over aging phenomenon.Cryogenic pretreatment makes the nose temperature of Cu-Cr-Zr alloy TTT curve slightly upward.