F. H.(Sam) Froes
,
C. Suryanarayana
,
and D. Mukhopadhyay (Institute for Materials and Advanced Processes (IMAP)
,
University of Idaho
,
Moscow
,
ID 83844-3026
,
USA)C-G. Li(BlM
,
P.O. Box 81
,
Beijing
,
100095
,
P.R. CHINA)K. Brand(On leave from Institut fur Werkstoffwissenshaft
,
Technische Universitst Dresden
,
07062 Dresden
,
Germany
,
at IMAP)
金属学报(英文版)
Mechanical alloying (MA), a solid-state powder processing method, is a "far from equilibrium" synthesis technique which allows development of novel crystal structures and microstructures, leading to enhanced physical and mechanical properties. The ability to synthesize a variety of alloy phases including supersaturated solid solutions, nanocrystalline structures, amorphous phases and intermetallic compounds themselves is discussed. No extension of solubility using MA has been observed in the intermetallics studied. Nanostructured grains were observed in all compositions. Long time milling generally resulted in amorphous phase formation in large part because of the increase in grain boundary energy/mole with reduced grain size; good agreement with the Miedema model for amorphization was obtained in the Al-Fe system. Generally an anneal was required to form the intermetallic after MA; however,intermetallics with a large negative enthalpy of formation were detected in the MA condition. A study of the hot isostatic pressing of γ-TiAl powders produced by MA demonstrated that full density can be achieved at least 400℃ below the normal temperature required for conventional powder, that is 725℃ or below. Nanometered sized grains (≤100nm)were observed after HIP'ing up to 850℃.
关键词:
: Intermetallics
,
null
,
null
LUO Zhiping
,
ZHANG Shaoqing
,
SONG DeyuBeijing Institute of Aeronoutical Materials
,
Beijing
,
100095
,
ChinaTANG Yali
,
ZHAO DongshanZhengzhou Institute of Technology
,
Zhengzhou
,
450002
,
China Manuscript received
,
27 April 1994
金属学报(英文版)
In the as-cast Mg-Zn-Zr-Y alloys, the quasicrystal phases show massive and eutectoid plate morphologies. The selected area dijfraction(SAD) revealed that a large pan of the quasicrystals are face-centered icosahedral (FCI), while a small amout of the quasicrystals belong to the simple icosahedral (SI) phase. It was found that in homogenized alloys, a part of the grain boundry phases was dissolved,and small massive W-phase and lath-shape MgZn_(2) phase dispersedly precipitate in the grains. The transformation of the quasicrystals relates to the temperature. After homogenizing at 360 ℃ , the quasicrystals still present, while after homogenizing at 400 ℃ , the quasicrystals transformed into a new C-type orthorhombic phase witha = 0.975 nm, b = 1.137nm and=0.935 nm.
关键词:
Mg-Zn-Zr-Y alloy
,
null
,
null
HAN Yafang (Institute of Aeronautical Materials
,
Beijing
,
100095
,
China)CHATURVEDIMC(University of Manitoba Winnipeg
,
Manitoba
,
Canada
,
R3T2N2)
金属学报(英文版)
A high performance Ni-Al-Mo-B system cast Ni_3Al base alloy, named Alloy IC6, has been developed for advanced gas turbine blades and vanes. The alloy has high strength and ductility from room temperature to 1100℃ as well as excellent creep resistance over a wide temperature range of 760℃ to 1100℃ . The superior mechanical properties of this alloy.may be attributed to (1) solid solution hardening by the large amount of Mo addition , (2)second phase strengthening by γ-phase and other minor phases that precipitate in various temperature ranges, (3) rearrangement of γ-phase in the form of raft structure during creep deformation , (4) high-density misfit dislocation networks at the γ /γ' interfaces that form due to a high value ofγ /γ ' misfit .
关键词:
: Ni_3Al Alloy
,
null
,
null
