Cu-9Ni-2.5Sn-1.5Al-0.5Si合金热处理工艺及性能研究

【作者】 洪斌；

【导师】 汪明朴；

【作者基本信息】 中南大学 ， 材料物理与化学， 2004， 硕士

【摘要】 本文以Cu-9Ni-2.5Sn-1.5Al-0.5Si合金为研究对象，利用金相观察、SEM、TEM、能谱分析及电导率、硬度的测量等方法，研究了添加0.5％Si和1.5Al％对Cu-9Ni-2.5Sn合金组织和性能的影响。研究发现： （1）Cu-9Ni-2.5Sn-1.5Al-0-5Si合金的铸态组织分明显枝晶组织：枝晶内是贫Sn、富Ni的Cu-Ni固溶体，枝晶间为富Sn相。 （2）Cu-9Ni-2.5Sn-1.5Al-0.5Si合金的铸态组织存在Sn的宏观反偏析，Sn的含量基本上从外到内呈现下降趋势。均匀化退火能一定程度，但不能完全消除Sn的反偏析。 （3）提高均匀化退火温度可以大大减少均匀化退火时间。实验合金适宜的均匀化退火工艺为960℃、1小时均匀化退火。 （4）Cu-9Ni-2.5Sn-1.5Al-0.5Si合金添加少量的Al和Si在固溶态能生成新相Ni₂Si和Ni₂Al。时效过程中，由于Ni₂Si和Ni₂Al相的析出使合金导电率在一定程度上有所提高。 （5）Cu-9Ni-2.5Sn-1.5Al-0.5Si合金在时效过程中硬化曲线呈现单峰形状。随着温度的升高，达到硬度峰值所需的时间越短。480℃时效只需1.5小时即可达到峰值，450℃时效则需3.5小时左右，但二者的硬化峰值相差不大。新相Ni₂Si在时效过程中产生沉淀强化，从而使Cu-9Ni-2.5Sn-1.5Al-0.5Si合金的硬度比Cu-9Ni-2.5Sn合金大大提高。 （6）对Cu-9Ni-2.5Sn-1.5Al-0.5Si合金，时效前的冷变形度越大，就越有利于该合金在时效中脱溶沉淀，缩短合金达到峰值的时间。 （7）在峰时效的样品中，得到了基体和析出物的两套斑点，由衍射花样标定结果可知析出物与基体晶格存在确定的位向关系，可用以下公式表示： （8）Cu-9Ni-2.5Sn-1.5Al-0.5Si合金中析出物对材料的强化作用，遵循中南大学硕士学位论文摘要orowan机制，即位错绕过析出物并且留下位错环。当时效强化型合金中第二相以Orowan机制产生强化效应时，材料强度升高的幅度与基体中析出物的平均间距成反比。材料中析出物体积分数一定，析出物的尺寸越小时，数量就越多，平均间距越小，强化作用也更显著。更多还原

【Abstract】 In this paper, by the means of metallomicroscopy, SEM, TEM, energy spectrum and the measurement of conductivity and hardness, the effect of added 0.5%Si and 1.5%A1 on the microstructure and properties of Cu-9Ni-2.5Sn alloy is studied. It is found that:(1) The cast structure of Cu-9Ni-2.5Sn-0.5Si-l.5%A1 alloy has three zones:Treelike crystal is inner layer consisted of Cu-Ni solid solution with poor Sn and rich Ni. Outer layer of treelike crystal is rich Sn phase , Ni2Si and Ni2Al phases containing a little Cu. These phases are consisted of the second layer. Between two layers, it is complex structural transitional zone.(2) There exists Sn negative segregation in the cast structure by macro-observation and the content of Sn decreases from outside to inside. The action of homogenized annealing can eliminate the segregation of treelike crystal, however, not eliminate Sn negative segregation.(3) Temperature increasing of homogenized annealing can greatly reduce time of homogenized annealing. Too high temperature makes alloy overburning, produce burnt structure in grain boundary. Proper homogenized annealing technology is 960 ℃\ 1 hours.(4) Added little Si and Al in Cu-9Ni-2.5Sn alloy produce Ni2Si and Ni2Al phrase. During ageing, Ni2Si and Ni2Al precipitation makes conductivity increase.(5) During ageing, the ageing hardened curve is the shape of unimodal. With the increasing of ageing temperature, time is shortened reaching hardness peak. It takes 1.5 hours at 480癈 ageing, 3.5 hours at 450癈 ageing. The peak of them is not different greatly. Ni2Si phase produces additional deposited harding so that the hardness of Cu-9Ni-2. 5Sn-l. 5A1-0. 5Si alloy is higher than Cu-9Ni-2. 5Sn alloy.(6) For Cu-9Ni-2. 5Sn-l. 5A1-0. 5Si alloy , that the cold is greater before ageing is favorable for its precipitation-hardening during ageing and the time arrived toABSTRACTpeak strength is shortened(7) In the sample of peak strength during ageing, we obtain two kinds of diffraction spots of matrix and precipitate. These diffraction spots are indexed .On the basis of it , we know that the orientation relation between the matrix and precipitate has been found to be:(H0)m//(21l)m- [110]m//[324]pp,(8) The material is strengthened by the precipitate in Cu~9Ni-2. 5Sn-l. 5A1-0. 5Si alloy by Orowan mechanism, namely, the dislocation passes round the precipitate and leaves a dislocation loop. When the second-phase in the ageing-hardening alloy generates strengthening effect by Orowan mechanism, the increasing strengthen is inverse proportion to the average spacing of the precipitate among the matrix. The capacity fraction of the precipitate in material is fixed. The smaller the precipitate’s size is, the larger its amount is and the smaller the average spacing is, so that the strengthening effect is more significant.更多还原