Effect of temperature on mechanical alloying of Cu-Zn and Cu-Cr system
(1. School of Earth Science and Resources, Chang’an University, Xi’an 710054, China;
2. State Key Laboratory for Mechanical Behavior of Materials,
School of Materials Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, China)
2. State Key Laboratory for Mechanical Behavior of Materials,
School of Materials Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, China)
Abstract: Cu-Zn and Cu-Cr powders were milled with an attritor mill at room temperature, −10, −20 and −30 ℃, respectively. Phase transformation and morphology evolution of the alloyed powder were investigated by X-ray diffractometry(XRD), X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy(SEM). The results show that lowering temperature can delay mechanical alloying(MA) process of Cu-Zn system with negative mixing enthalpy, and promote MA process of Cu-Cr system with positive mixing enthalpy. As for Cu-Cr and Cu-Zn powders milled at −10 ℃, lamellar structures are firstly formed, while fewer lamellar particles can be found when the powder is milled at −20 ℃. When the alloyed powder is annealed at 1 000 ℃, Cu(Cr) solid solution is decomposed and Cr precipitates from Cu matrix, whereas Cu(Zn) solid solution keeps stable.
Key words: Cu-Cr system; Cu-Zn system; mechanical alloying; phase transformation; mixing enthalpy