Crystallization Kinetics Of Cu Research Articles

Crystallization kinetics of Cu–Zr–Al bulk metallic glass with Nd addition

AbstractThe crystallization kinetics of (Cu48Zr48Al4)100−xNdx (x = 0, 2 at.%) bulk metallic glasses in nonisothermal and isothermal conditions were studied by differential scanning calorimetry and X‐ray diffraction (XRD). XRD analysis shows that the crystallization product Cu10Zr7 changes to Cu10Zr7 and Cu2Nd with Nd presence in nonisothermal and isothermal conditions. Crystallization activation energy was calculated in nonisothermal conditions using Kissinger and Ozawa methods and in isothermal conditions using Arrhenius model. The results show that the activation energy harbored by (Cu48Zr48Al4)98Nd2 expresses larger value compared with Cu48Zr48Al4, which indicate that the energy barrier for crystallization has enhanced along the Nd addition. The Johnson–Mehl–Avrami model was employed for analyzing the crystallization kinetics in isothermal condition. The Avrami exponent n for Cu48Zr48Al4 is more than 2.5, demonstrating that the crystallization is mainly governed by diffusion‐controlled three‐dimensional growth with increasing nucleation rate. Comparably, the Avrami exponent n for (Cu48Zr48Al4)98Nd2 is 1.5 < n < 2.5, suggesting that the crystallization is mainly determined by diffusion‐controlled three‐dimensional growth with decreasing nucleation rate. The evident enhancement in crystallization activation energy based on Nd addition is rationally made up of an influential factor commonly harbored on the enhanced glass forming ability for the rare‐earth comprising Cu–Zr–Al metallic glasses.

Effect of Medium Range Order on Crystallization Kinetics of Cu x Zr 1-x Thin Film Metallic Glasses

Effect of Medium Range Order on Crystallization Kinetics of Cu x Zr 1-x Thin Film Metallic Glasses

Glass-forming ability, thermal stability of B2 CuZr phase, and crystallization kinetics for rapidly solidified Cu–Zr–Zn alloys

The glass-forming ability (GFA) of (Cu0.5Zr0.5)100-xZnx (x = 1.5, 2.5, 4.5, 7, 10, and 14 at %) metallic glasses (MGs) was studied. With increasing Zn content, the GFA of CuZr-based MGs gradually increases, enabling the fabrication of Cu–Zr–Zn bulk metallic glasses (BMGs) and metallic glass matrix composites. The enhancement of GFA with Zn addition to the CuZr binary alloy is well explained by considering topological instability and electronic criteria. Upon annealing of Cu–Zr–Zn MGs Cu10Zr7 and subsequent CuZr2 crystals precipitate in the glassy matrix, being followed by the nucleation of B2 CuZr crystals. It is shown that Zn addition can effectively stabilize B2 CuZr phase to lower temperatures. Analysis of the crystallization kinetics of Cu–Zr–Zn MGs under isothermal conditions shows that the dominated crystallization mechanism is the interface-controlled two- or three-dimensional growth with different nucleation rates.

Glass transition behavior and crystallization kinetics of Cu 0.3(SSe 20) 0.7 chalcogenide glass

The glass transition behavior and crystallization kinetics of Cu 0.3(SSe 20) 0.7 chalcogenide glass were investigated using differential scanning calorimetry (DSC), X-ray diffraction (XRD). Two crystalline phases (SSe 20 and Cu 2Se) were identified after annealing the glass at 773 K for 24 h. The activation energy of the glass transition ( E g), the activation energy of crystallization ( E c), the Avrami exponent ( n) and the dimensionality of growth ( m) were determined. Results indicate that this glass crystallizes by a two-stage bulk crystallization process upon heating. The first transformation, in which SSe 20 precipitates from the amorphous matrix with a three-dimensional crystal growth. The second transformation, in which the residual amorphous phase transforms into Cu 2Se compound with a two-dimensional crystal growth.

Crystallization kinetics of Cu∕a-Si bilayer recording film under thermal and pulsed laser annealing

The crystallization kinetics of Cu∕a-Si bilayer recording film under thermal and pulsed laser annealing has been studied. Under thermal annealing, the crystallization temperature and activation energy for crystallization of a-Si with a thin Cu metal layer were reduced to about 485°C and 3.3±0.1eV, respectively. The reaction exponent was determined to be around 1.8, corresponding to a crystallization process in which grain growth occurs with nucleation, and the nucleation rate decreases with the progress of the grain growth process. Under pulsed laser annealing, the activation energy for crystallization of a-Si was estimated to be about 0.22eV which is significantly lower than that under thermal annealing and may be explained by the explosive crystallization of a-Si, while the reaction exponent was found to vary from 1.2 to 1.4, corresponding to a grain-growth-controlled process associated with instantaneous nucleation.

Crystallization kinetics of Cu xTi 100− x ( x=43, 50 and 53) glasses

The crystallization kinetics of Cu–Ti glass at three different compositions has been studied by differential scanning calorimetry (DSC). The DSC traces have been analyzed in terms of activation energy, stability and dimensionality of growth by four different models viz. the Kissinger equation, the Ozawa equation, the Matusita equation and the Gao and Wang equation. The activation energy increases with Cu content and the highest crystallization temperature occurs for the composition Cu 50Ti 50 indicating locally increased chemical short-range order at this particular composition. The average value of the Avrami exponent comes out to be 4 which shows that the crystallization process takes place via three-dimensional parabolic growth with bulk crystallization.