【摘要】 采用电弧熔炼和机械合金化,随后在750℃,58MPa下热压制备了晶粒尺寸差别较大的Cu40Ni40Cr20合金,用X射线衍射仪、扫描电镜等分析手段对比研究了显微组织结构。结果表明:电弧熔炼制备的晶粒尺寸较大的Cu40Ni40Cr20合金为二相,组织极其不均匀;采用机械合金化,通过控制热压条件制备的纳米晶Cu40Ni40Cr20合金仍为双相,但显微组织均匀,稳定。随着球磨时间的延长,由于晶粒细化和应变的结果,衍射峰偏移并有明显的宽化产生,Cu在Cr或Cr在Cu中的固溶度明显增加,当球磨60h后,合金已由双相变成亚稳态的单相。由于机械合金化的粉末处于非平衡态,其超固溶度溶质随热压和真空退火过程的进行会慢慢脱溶分解出来,合金已由单相变为两相,两相颗粒均成倍长大,但仍然保持纳米级尺度;机械合金化、热压和退火后样品中Cu,Ni和Cr的晶格均未发生崎变;讨论了晶粒细化对合金显微组织的影响。更多还原

【Abstract】 The Cu40Ni40Cr20 bulk alloys with much different grain size have been prepared respectively by conventional arc-melting (CA) and mechanical alloying (MA) . Their micro-structural characteristics were investigated by X-ray diffraction (XDR), scanning electron microscopy(SEM) and energy-dispersive X-ray microanalysis (EDX). The results show that the microstructure of CA Cu40Ni40Cr20 is composed of double phases but extremely not uniform, while that of MA Cu40Ni40Cr20 is also composed of double phases but uniform with excellent density. With increase of ball milling time, the X-ray diffraction peaks have a deviation and become wide because of fine grain size and internal stress whereas the solid solubility of Cu in Cr and Cr in Cu increased evidently. When powders are milled for 60h, the alloyed powers have become single solid solution. Because the mechanically alloyed powders are in non-equilibrium state, the solute super-saturation decompose slowly with hot pressing and annealing in vacuum and finally the alloys transformed double-phases from single phase solid solution. The sizes of the two phases particles increased but still remained nano-size range. The lattices of copper, nickel and chromium do not produce distortion in the course of mechanical alloying, hot pressing mechanically alloyed powders and annealing. The effect of grain size on alloys microstructure was discussed in detail.更多还原