枝晶间距及合金元素对Cu-15Ni-8Sn合金塑性成型性能的影响
发布时间:2018-04-11 03:01
本文选题:Cu-15Ni-8Sn + 冷变形 ; 参考:《江苏科技大学》2017年硕士论文
【摘要】:本文分别采用中频感应炉与高频感应炉对Cu-15Ni-8Sn合金进行熔炼制样,探索合金铸态枝晶间距对后续热处理过程中组织与性能的影响。在分别添加微量Cr、Zr、Si、Nb、Ti、Mn元素后,研究这些微量合金元素对Cu-15Ni-8Sn合金在均匀化退火与固溶处理、冷变形与时效处理过程中组织与性能的变化。确定能延缓低熔点不连续沉淀产物析出的条件,从而改善合金塑性成形工艺性能。与此同时,研究合金元素含量对Cu-15Ni-8Sn合金调幅分解组织与性能的影响。研究表明:铸态枝晶间距缩减至11μm左右的Cu-15Ni-8Sn合金经840℃×8h均匀化退火与800℃×1h固溶处理后组织已趋于均匀,当枝晶间距达到50μm时Cu-15Ni-8Sn合金在同等热处理工艺条件下,溶质扩散不均匀,依旧存在残余未溶组织。而初生呈亮白色的未溶组织属于富锡相。溶质扩散不均匀的Cu-15Ni-8Sn合金分别在80%或60%冷轧变形后,80%冷轧变形试样在400℃×0.5h时效处理后达到硬度峰值394HV,60%冷轧变形试样在400℃×1h时效处理后达到硬度峰值392HV,但随时效时间的继续延长其硬度值皆急剧下降。而溶质扩散较均匀的Cu-15Ni-8Sn合金,经60%冷镦粗变形及400℃×5h时效后达到395HV的硬度峰值。微量Nb与Si能延缓Cu-15Ni-8Sn合金在均匀化退火过程中的溶质扩散效果,经60%冷镦粗变形的试样边缘有裂纹,时效处理时不连续沉淀产物呈提前析出趋势,400℃×5h时效后的硬度分别为300HV与365HV;添加微量Zr的Cu-15Ni-8Sn合金60%冷镦粗变形后试样边缘未出现裂纹,但在400℃×5h时效处理后大量析出不连续沉淀产物,而硬度仅有287HV;添加微量Ti的Cu-15Ni-8Sn合金在60%冷镦粗变形后边缘虽有裂纹产生,但在时效阶段不连续沉淀产物的析出与变形量成正比,试样边缘高变形区的析出与生长较快、试样中心区域析出与生长较平稳,400℃×5h时效处理后硬度达到393HV;添加微量Mn的合金不仅60%冷镦粗变形后试样边缘未开裂,在400℃×5h时效处理后试样边缘高变形区也未大量析出不连续沉淀产物,硬度值为387HV;添加微量Cr的合金在400℃×5h时效处理后的组织与性能略逊于含Mn合金,硬度值为369HV。对更多Mn元素含量的Cu-15Ni-8Sn合金组织与性能进行研究,结果表明添加0.87wt%Mn与0.38wt%Mn在延缓不连续沉淀产物的效果相近,随Mn含量的提高Cu-15Ni-8Sn合金时效硬化的峰值时间被延迟。因此,添加0.38wt%Mn的Cu-15Ni-8Sn合金综合工艺性能最佳。
[Abstract]:In this paper, Cu-15Ni-8Sn alloy samples were prepared by medium frequency induction furnace and high frequency induction furnace, respectively, and the effect of as-cast dendrite spacing on microstructure and properties of Cu-15Ni-8Sn alloy during subsequent heat treatment was investigated.The microstructure and properties of Cu-15Ni-8Sn alloy during homogenization annealing, solution treatment, cold deformation and aging treatment were studied after adding trace elements of Cr-ZrZirn, Si-Nb and Ti-Mn respectively, and the microstructure and properties of the alloy were studied during homogenization annealing, solution treatment, cold deformation and aging treatment.The conditions which can delay the precipitation of discontinuous precipitation products at low melting point are determined, and the process properties of alloy plastic forming are improved.At the same time, the effect of alloy element content on the microstructure and properties of Cu-15Ni-8Sn alloy was studied.The results show that the microstructure of the as-cast Cu-15Ni-8Sn alloy reduced to about 11 渭 m after homogenization annealing at 840 鈩,
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