机械球磨和高压对Co相变的影响

通过高能球磨和高压技术对Co的相变过程及其机制进行研究, 结果表明, 具有六角密积结构的α-Co经60 h高能球磨后完全转变为具有面心立方结构的β-Co, 但继续球磨直到120 h, 未观察到β-Co向α-Co的逆转变. 由于球磨碰撞引起的缺陷层错和局域温度导致α-Co到 β-Co的转变. 研究发现, 高压下β-Co向α-Co相转变, 由于β-Co向α-Co的相转变为无扩散相变, 因此, 压力可使其形核热力学势垒降低, 即压力对β-Co向α-Co的相转变具有促进作用. 

Effects of Mechanical Milling and High Pressure on Phase Transition of Cobalt

Phase transition of cobalt induced by mechanical milling and high pressure and its transition mechanisms were studied. α-Co with the hcp. structure completely transformed to β-Co with the fcc. structure after milling for 60 h due to the stacking fault and local temperature resulted from impact and shear force of steel balls during the milling process. However, the reverse transition from β-Co to α-Co was not observed, even milling up to 120 h.The reverse transition was studied under high pressure, and it was found that pressure can accelerate the transition from β-Co to α-Co, which is due to that this transformation is a diffusionless one and its thermodynamic barrier decreases by pressuring.