Thermally assisted and mechanically driven solid-state reactions for formation of amorphous Al{sub 33}Ta{sub 67} alloy powders
- Tohoku Univ., Sendai (Japan). Inst. for Materials Research
The rod milling technique using the mechanical alloying (MA) process has been employed for preparing amorphous Al{sub 33}Ta{sub 67} alloy starting from elemental Al and Ta powders. X-ray diffraction (XRD), differential thermal analysis (DTA), differential scanning calorimetry (DSC), optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are utilized to follow the progress of amorphization. The results show that during the first few kiloseconds of MA time, layered composite particles of Al and Ta are intermixed and form an amorphous phase upon heating to 685 K by DTA. This process is called thermally assisted solid-state amorphization (TASSA). During the early stage of milling, the number of layers of the composite particles increases. This leads to an increase in the heat formation of amorphous Al{sub 33}Ta{sub 67} alloy via the TASSA process, {Delta}H{sub a}{sup TASSA} becomes zero. After 1,440 ks (400 hours) of MA time, a homogeneous amorphous phase is formed. The amorphization process in this case is attributed to a mechanical driven solid-state amorphization (MDSSA). The heat of formation of the amorphous phase formed via the MDSSA process, {Delta}H{sub a}{sup MDSSA}, has been calculated. Moreover, the crystallization characteristics indexed by the crystallization temperature, and the enthalpy of crystallization, of the amorphous phases formed by TASSA and MDSSA processes are investigated as a function of MA time. The role of amorphization via each process has been discussed.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 417881
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 27, Issue 10; Other Information: PBD: Oct 1996
- Country of Publication:
- United States
- Language:
- English
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