Study on Aging Kinetics of CuNiSi Alloy

Precipitation behavior of the early aging stage and the transformation kinetics were studied by analysing the electrical resistance variation of the solution Cu-Ni-Si alloy in the process of aging. Due to the linear relationship between electrical conductivity and volume fraction of precipitates, the transformation kinetics equation can be educed from the Avrami empirical formula, on the basis of this equation, transformation kinetics curve and “C” curve of the isothermal transformation were established.     

Effect of Ti addition on tensile properties of Cu-Ni-Si alloys

This study examines how varying Ni and Si contents and the addition of Ti affect the tensile behavior of Cu-Ni-Si alloys with different aging conditions. Cu-3Ni-0.7Si and Cu-6Ni-1.4Si alloys, both with and without the addition of Ti, were prepared by solution-heat treatment at 950 °C for 2 h, then aged at 500 °C for 1/ 6 h, 1/3 h, 1/2 h, 1 h, 3 h and 6 h, before tensile tests were conducted. Doubling the Ni and Si contents in Cu-Ni-Si alloys greatly increased the tensile strength and grain refinement, while marginally reducing the tensile elongation. Meanwhile, adding Ti to Cu-Ni-Si alloys reduced the grain size and greatly increased the tensile elongation. The aging response was also significantly accelerated by the addition of Ti. However, the expected improvement in tensile strength was not obtained by adding Ti, addition due to the agglomeration of coarse Ni₂Si precipitates and the accelerated lamellar structure formation. Finally, we discuss the microstructural changes that result from variations in aging time, different Ni and Si contents and the addition of Ti on Cu-Ni-Si alloys based on detailed optical, scanning electron microscope (SEM) and transmission electron microscope (TEM) micrographic observations and SEM fractographic analysis.     

Optimization of conductivity and strength in Cu-Ni-Si alloys by suppressing discontinuous precipitation

Cu-Ni-Si alloys with and without Ti were solution treated at 980 °C for 1 h and cooled by air cooling and water quenching, after which the specimens were aged at 500 °C. The two alloys showed different aging characteristics with different cooling rates during the aging process. The conductivity of all alloys increased during aging; for alloys that were water quenched, hardness increased at the early stage of aging and then drastically decreased. The air-cooled Cu-Ni-Si alloy without Ti also experienced an increase in hardness, which then decreased during aging, but the air-cooled Cu-Ni-Si alloy with Ti did not show a drastic decrease in hardness during prolonged aging. A combination of yield strength and conductivity of 820 MPa and 42% IACS, respectively, was achieved in the air-cooled Cu-Ni-Si-Ti alloy after solution treatment.     

Cu-Ni-Si合金析出物对再结晶的影响

通过分析时效期间Cu-Ni-Si合金显微硬度、导电率以及微观组织的变化,研究了析出相和再结晶行为的相互作用.结果表明,时效初期析出相对随后的再结晶过程具有强烈阻碍作用.在450、550℃较低温度时效时,合金发生原位再结晶,析出相在其体积分数略微升高或不变的情况下发生粗化;导电率上升趋势为先快后慢并趋于稳定,因而其变化曲线上无峰值出现;显微硬度则由于时效后期析出颗粒粗化,析出强化效果降低而出现峰值.在750℃高温时效时,合金发生不连续再结晶,析出相则在体积分数略有降低的情况下发生粗化;导电率先快速上升后缓慢下降因而出现峰值;而显微硬度由于析出物迅速粗化而一开始就表现为持续下降.

Abstract：

By analyzing the change of microhardness, electric conductivity and microstructure of Cu-Ni-Si ahoy during aging, the interaction between precipitated phase and recrystallization was studied. Results show that precipitates phase in early aging stage can strongly prevent recrystallization. When aging at 450℃ and 550℃, recrystallization in site occurred,and precipitates phase grew with no significant change of its volume fraction. Electric conductivity monotonously increased and microhardness increased first to a maximum value and then decreased for the alloy with increasing aging time. When aging at 750 ℃, discontinuous recrystallization occurred,and precipitates phase with slightly decreasing of its volume fraction as aging time increased. However, a peak in curve of electric conductivity vs. aging time is observed and microhardness decreased continuously for the alloy with increase of aging time.     

引线框架材料Cu-Ni-Si系合金的发展

概述了引线框架用Cu-Ni-Si合金的研究现状。介绍了Cu-Ni-Si合金中Ni、Si元素的含量及其质量比对Cu-Ni-Si合金性能的影响,合金化特点,时效过程中的组织转变及热处理工艺和Zn、P、Ag、Cr、Al、稀土等微量元素对Cu-Ni-Si合金硬度、电导率等性能的影响。     

Cu-Zr和Cu-Zr-Si的时效析出特性及冷变形对时效析出的影响

测定了Cu-Zr和Cu-Zr-Si时效后硬度、电导率的变化。分析了影响电导率的因素。认为Si可以细化析出物、提高材料的抗软化能力。对形变后时效时材料性能的改善及变形度的影响进行了讨论。     

用导电率研究Cu-Cr-Zr-Y合金的相变动力学

通过测量Cu-Cr-Zr-Y合金时效过程中的导电率变化和导电率与时效析出相的转变量之间的内在关系,计算出时效过程中析出相的转变比率,并确定了不同温度下描述时效析出相转变比率与时效时间关系的Avrami经验方程.在此基础上,确定了一定温度下导电率随时效时间变化的导电率方程.同时用固态热分解反应机理的微分方程,验证了用Avrami经验方程来描述合金的析出过程是正确的.     

Influence of Cryorolling on the Precipitation of Cu–Ni–Si Alloys: An In Situ X-ray Diffraction Study

The effect of cryorolling on the precipitation process of deformed Cu–Ni–Si alloys was investigated through in situ synchrotron X-ray diffraction technique. The results demonstrate that the precipitation process is significantly accelerated by cryorolling. Cryorolling produces higher dislocation density, which provides more heterogeneous nucleation sites for Ni2 Si precipitates, hence promotes precipitation. In the early stage of aging, the enhanced nucleation of precipitates accelerates the depletion of supersaturation, and finer precipitates are obtained. In addition, recrystallization is promoted as a result of high stored energy in the cryorolled Cu–Ni–Si alloys, which facilitates the formation of discontinuous precipitation in the late stage of aging.     

Cu-Ni-Si合金二次时效时的再结晶行为

利用透射电镜、显微硬度法和电导率法,研究了Cu-Ni-Si二次时效过程中显微组织、硬度及导电率变化情况.结果表明:二次时效可使合金在较短的时效时间内获得更高的导电率,经预时效后冷变形的合金,溶质原子可借助密集且分布均匀的位错网络由铜基体快速传输至析出物处或析出物的形核部位完成析出过程,使铜基体得到快速的净化,从而获得较高的导电性.Cu-3.2Ni-0.75Si合金经预时效 变形后的时效过程中,可发生原位再结晶和不连续再结晶两种形式的再结晶.再结晶的形式主要决定于预时效时析出相的大小和冷变形的程度,稳定细小的析出相促使原位再结晶的发生,原位再结晶使合金微观组织中析出相比较细小,因而保持较高的硬度;亚稳的析出相在再结晶过程中将向稳定相转变,相变动力与形变储存能共同作用促使合金发生不连续再结晶,使合金硬度迅速下降,析出相快速粗化.     

Microstructure and Properties of a High-Strength Cu-Ni-Si-Co-Zr Alloy

A high-strength Cu-Ni-Si alloy was developed with the additions of Co and Zr. The aging curve for the alloy was generated using hardness. Electron microscopy studies were conducted to analyze the phases in the alloy. Two types of phases, one of copper matrix and the other of Ni-Si-Co-Zr intermetallic phase, could be identified using scanning electron microscopy. Transmission electron microscopy studies confirmed the presence of two types of precipitates in solution-treated and aged (STA) condition, i.e., Ni₂Si and Co₂Si. Mechanical properties and electrical conductivity were evaluated in solution-treated (ST) and STA conditions. Aging of the ST samples at 500 °C for 3 h has shown an increase of 72 and 15% in yield strength (YS) and electrical conductivity, respectively. This increase in YS and conductivity on aging is primarily attributed to the formation of fine Ni₂Si and Co₂Si precipitates.     

AGING PRECIPITATION OF Cu-Zr AND Cu-Zr-Si ALLOYS AND AFFECTED BY COLD WORKING

The hardness and electrical conductivity of Cu-Zr and Cu-Zr-Si alloys varying with differ-ent aging regimes were measured and the factors influencing the electrical conductivity wereanalysed.It is believed that a little Si can refine the precipitates and improve the resistance tosoftening.The improvement of materials properties by aging and the effect of cold work werealso discussed.     

Y对Al-Zr合金微观组织与性能的影响

采用电导率、显微硬度、扫描电子显微镜（SEM）和透射电子显微镜（TEM）研究Al-0．30Zr与Al-0．30Zr-0．08Y合金的微观组织与性能。铸态Al-Zr-Y合金中微米尺度初生Al3Y相通过共晶反应在晶内和晶界上同时生成。在Al-Zr-Y合金中,Y明显加速了Al3Zr（Ll2）的析出动力学。由于较大体积Al3（Zr,Y）析出相的生成,Al-Zr-Y合金的电导率明显高于Al-Zr合金的。在Al-Zr-Y合金中观察到了高密度的弥散球状Ll2结构Al3（Zr-Y）析出相。Al-0．30Zr-0．08Y合金具有比Al-0．30Zr合金更强的抗再结晶能力。     

Modeling of precipitation hardening in pre-aged AlMgSi(Cu) alloys

A new analytical method to estimate the evolution of the relative volume fraction of precipitates during artificial aging of pre-aged AlMgSi(Cu) alloys in the underaged regime is introduced. The analytical results demonstrate that the precipitation processes in AlMgSi(Cu) alloys are isokinetic in commercially relevant temperature ranges. The theory of transformations is used to model isothermal and non-isothermal aging kinetics in isokinetic systems where the precipitate nuclei pre-exist at the start of aging and definite precipitate contents are reached at the end of transformation. A simple physically based model is also developed for the prediction of the average size of precipitates during artificial aging of pre-aged alloys, when “growth” is the controlling mechanism of precipitation. The microstructural models are combined with a previously developed yield strength model and the evolution of yield strengths during isothermal and non-isothermal aging of AlMgSi(Cu) alloys, with various pre-aging histories, are modeled. The analytical method and the microstructural and yield strength models are validated using experimental results.     

Effect of V addition on hardness and electrical conductivity in Cu-Ni-Si alloys

The effect of vanadium (V) addition on the microstructure, the hardness and the electrical conductivity of Cu-2.8Ni-0.7Si alloys was investigated. The V-free, the 0.1 wt% V-added, the 0.2 wt% V-added Cu base alloys were exposed to the same experimental conditions. After the cold rolling of the studied alloys, the matrix was recrystallized during the solution heat treatment at 950 °C for 2 h. However, small amounts of vanadium substantially suppressed the recrystallization and retarded the grain growth of the Cu base alloys. The added vanadium accelerated the precipitation of Ni₂Si intermetallic compounds during aging and therefore it contributed positively to the resultant hardness and electrical conductivity. It was found that the hardness and the electrical conductivity increased simultaneously with increasing aging temperature and time with accelerated precipitation kinetics by the addition of vanadium. In the present study, the Cu-2.8Ni-0.7Si alloy with 0.1 wt%V was found to have an excellent combination of the hardness and the electrical conductivity when it was aged at 500 °C.     

高强高导电CuCrZr合金时效过程中析出相的演化规律

对固溶态CuCrZr合金经不同温度时效后的析出相进行显微观察,并对其电导率进行了测试。结果表明:450 ℃时效30 min的析出相为5 nm以下的单质Cr相,并且与基体呈cube-on-cube取向关系。450 ℃峰值时效120 min时析出相为CrCu₂Zr相和Cr相,尺寸为10nm左右,且与基体共格;600 ℃和800 ℃过时效30 min后析出相主要演变为球状的Cr相和棒状的Cu₄Zr相。在600 ℃时效处理后部分棒状析出相已显著长大至50 μm左右,而800 ℃时效处理后几乎看不到细小的析出相,其中棒状Cu₄Zr析出相长大至200 μm以上,球状纯Cr析出相也接近50 μm。CuCrZr合金在450 ℃时效时导电率随时效时间的延长不断增高,在120 min后达到最大值且几乎不再变化。根据析出相转化率与导电率的线性关系,建立了合金在400、450、500和600 ℃下的析出动力学方程。     

Cu-Be-Co-Zr合金时效析出动力学

研究了Cu-Be-Co-Zr合金480℃恒温时效条件下的时效析出动力学。根据导电率与析出相体积分数的关系,计算了Cu-Be-Co-Zr合金不同时效时间(0, 30, 60, 120, 180, 240, 360, 480, 600 min)对应的析出相转变比率,建立了Cu-Be-Co-Zr合金480℃时效条件下的析出相变动力学方程和导电率方程,并在此基础上绘制了等温转变动力学S曲线;采用固态热分解反应机理的积分方程,揭示了Cu-Be-Co-Zr合金时效析出转变机制为受扩散控制的反应机理。     

铝合金中Mg_2Si相的时效析出过程

描述了Al-Mg-Si/Al-Si-Mg系合金时效析出的一般序列为α-sss→GP 区→β"→β'→β(Mg_2Si),总结了在析出序列中可能出现的各亚稳相的晶体结构模型,讨论了各阶段析出相的形成或转变过程及其强化作用;并就过量的Si、Cu、大塑性变形等对析出相的影响作了探讨.     

冷轧Cu-Cr-Zr-Co-Si合金的时效行为

通过测量Cu-Cr-Zr-Co-Si冷轧合金在等温时效过程中导电率的动态变化,基于合金导电性能与析出相转化率间的近似线性关系,建立了不同冷变形量下合金时效析出过程的动力学Avrami方程及曲线,在此基础上分析了再结晶与时效析出的相互影响.结果表明:Cu-Cr-Zr-Co-Si合金形变时效过程中,随变形量和时效时间的增加...     

Cu-2.8Ni-0.7Si-0.15Mg合金的时效性能

对不同变形量的Cu-Ni-Si-Mg合金进行时效处理,研究了变形量、时效温度及时效时间对合金性能的影响。结果表明,时效前的预冷变形能够促进合金在时效过程中第二相的析出,从而提高合金的显微硬度和导电率。当合金经60%的冷变形,在450℃时效1 h,能获得较高的显微硬度与导电率,分别达到242 HV0.2和35.5%IACS。同时建立了该合金在450℃下,关于时效时间的相变动力学方程和导电率方程。     

高强度Cu-Ni-Si系引线框架材料研究进展

综述了引线框架用Cu-Ni-Si材料中Ni、Si元素质量比及含量对Cu-Ni-Si合金性能的影响。归纳总结了Cu-Ni-Si合金的强化机制、影响电导率的因素,并简单列举了Cr、Zn、P、Al微量元素加入的机理．介绍了不同热处理工艺对Cu-Ni-Si系合金性能的影响。