X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were usedto investigate the crystallization process of amorphous Al_(90)TM_xCe_(10-x), (atom fraction inpercent; TM = Fe or Ni; x = 3, 5) alloys. Agi...X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were usedto investigate the crystallization process of amorphous Al_(90)TM_xCe_(10-x), (atom fraction inpercent; TM = Fe or Ni; x = 3, 5) alloys. Aging effects were examined by X-ray diffraction. Thestructure corresponding to the prepeak for the amorphous Al_(90)Fe_5Ce_5 alloy is more stable thanthe amorphous matrix, but it is not stable for amorphous Al_(90)Ni_5Ce_5 alloy during the firstcrystallization stage and even decomposes at room temperature. Although both Al-Ni and Al-Fe havestrong chemical bonding, the crystallization onset temperature of amorphous Al-Fe-Ce alloys is muchhigher than that of amorphous Al-Ni-Ce alloys, which is likely caused by the different stability ofthe structure corresponding to the prepeak. The crystallization onset temperature increases as Ce/Niratio increases in amorphous Al_(90)Ni_xCe_(10-x) alloys, whereas it decreases as Ce/Fe ratioincreases in amorphous Al_(90)Fe_xCe_(10-x) alloys. A better atomic packing produces as Ce contentincreases because of the size mismatch in Al-Ni-Ce systems and as Fe content increases because ofthe increasing Fe central structural units.展开更多
The disaccommodation(DA)measurements of initial susceptibility were performed in amorphous Fe_(90-x)Ni_xZr_(10)(x=10,20,30)alloys.The DA was measured for two different amorphous states:as-quenched and pretreated at 53...The disaccommodation(DA)measurements of initial susceptibility were performed in amorphous Fe_(90-x)Ni_xZr_(10)(x=10,20,30)alloys.The DA was measured for two different amorphous states:as-quenched and pretreated at 537 K for 45 min.For all the as- quenched samples,in the isochronal spectra of DA a well defined relaxation peak around 350 K is accompanied by a samll but distinct peak near the Curie temperature of Fe_(90)Zr_(10) phase(T_c=230 K).The reversibility and annealing effect on DA are analyzed within the framework of two-level model.The fits of the theory to the experimental data of reversible relaxation processes gave a spectrum,of activation energies and pre- exponential factor.展开更多
基金This work was financially supported by the Natural Science Foundation of Shandong Province (No. Y2000b02)
文摘X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were usedto investigate the crystallization process of amorphous Al_(90)TM_xCe_(10-x), (atom fraction inpercent; TM = Fe or Ni; x = 3, 5) alloys. Aging effects were examined by X-ray diffraction. Thestructure corresponding to the prepeak for the amorphous Al_(90)Fe_5Ce_5 alloy is more stable thanthe amorphous matrix, but it is not stable for amorphous Al_(90)Ni_5Ce_5 alloy during the firstcrystallization stage and even decomposes at room temperature. Although both Al-Ni and Al-Fe havestrong chemical bonding, the crystallization onset temperature of amorphous Al-Fe-Ce alloys is muchhigher than that of amorphous Al-Ni-Ce alloys, which is likely caused by the different stability ofthe structure corresponding to the prepeak. The crystallization onset temperature increases as Ce/Niratio increases in amorphous Al_(90)Ni_xCe_(10-x) alloys, whereas it decreases as Ce/Fe ratioincreases in amorphous Al_(90)Fe_xCe_(10-x) alloys. A better atomic packing produces as Ce contentincreases because of the size mismatch in Al-Ni-Ce systems and as Fe content increases because ofthe increasing Fe central structural units.
文摘The disaccommodation(DA)measurements of initial susceptibility were performed in amorphous Fe_(90-x)Ni_xZr_(10)(x=10,20,30)alloys.The DA was measured for two different amorphous states:as-quenched and pretreated at 537 K for 45 min.For all the as- quenched samples,in the isochronal spectra of DA a well defined relaxation peak around 350 K is accompanied by a samll but distinct peak near the Curie temperature of Fe_(90)Zr_(10) phase(T_c=230 K).The reversibility and annealing effect on DA are analyzed within the framework of two-level model.The fits of the theory to the experimental data of reversible relaxation processes gave a spectrum,of activation energies and pre- exponential factor.
