Structure and properties of mechanically alloyed and consolidated Ni-W(fe) alloys.
When the W content of Ni-W powder blends is sufficiently high, the powder amorphizes when mechanically alloyed in high energy mills. Milling is accompanied by wear of the grinding media. If the media are Fe based, amorphous ternary W-Ni-Fe alloys are formed on alloying. The amorphous structure is not maintained during consolidation at high temperature, which instead yields a three-phase (W, (Ni-Fe)W intermetallic, and Ni rich FCC) fine micro structure. This paper reports on evolution of microstructure during consolidation and subsequent heat-treatment of such mechanically alloyed powders. The phases present, their compositions, and their relative amounts have been determined. As-consolidated structures are non equilibrium. They contain the (Ni-Fe)W phase in amounts greater than the equilibrium one. Thus this phase dissolves on heat-treatment. However, if the Fe/Ni atomic ratio of the alloy is sufficiently high, some intermetallic remains after extended heat-treatment. Strengths and hardnesses (but not toughnesses) of these materials are much higher than they are for heavy metals produced by liquid phase sintering. By substituting zirconium-boron additions for titanium-boron additions in the weld deposit, further understanding of the role of specific microalloying additions on the suppression of grain boundary ferrite and the promotion of the intragranular formation of acicularferrite in low carbon steel weld metal is achieved.
- Research Organization:
- Michigan Technological Univ., Houghton, MI (United States). Dept. of Metallurgical Engineering
- OSTI ID:
- 147362
- Report Number(s):
- AD-A--296018/5/XAB; CNN: Contract DAAH04-94-G-0315
- Country of Publication:
- United States
- Language:
- English
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