排序方式: 共有61条查询结果,搜索用时 15 毫秒
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Belcher Calvin H. Zheng Baolong MacDonald Benjamin E. Langlois Eric D. Lehman Benjamin Pearce Charles Delaney Robert Apelian Diran Lavernia Enrique J. Monson Todd C. 《Journal of Materials Science》2022,57(9):5518-5532
Journal of Materials Science - For transformers and inductors to meet the world’s growing demand for electrical power, more efficient soft magnetic materials with high saturation magnetic... 相似文献
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Diana A. Lados Diran Apelian Libo Wang 《Metallurgical and Materials Transactions B》2011,42(1):171-180
The effects of solution treatment time and Si content and morphology on microstructures and mechanical properties of heat-treated Al-Si-Mg cast alloys were investigated systematically. Five alloys, with Si levels ranging from 1 to 13 pct, were tested in as-cast, T4, and T61 conditions. The eutectic Si was both unmodified and Sr-modified. Results show that the microstructures are affected significantly by alloy composition, eutectic Si morphology, and solution treatment time. Si content has significant effects on ultimate tensile strength (UTS), yield strength (YS), and elongation as well as a strong influence on solution treatment response. In T61 treatment with different solutionizing times, UTS and YS reach their maximum values in ~1 hour of solutionizing followed by a decrease, then a slight increase, and finally, a plateau close to the maximum level. Elongation of alloys with a high Si content, 7 pct and 13 pct, increases rapidly at solutionizing times of 1 to 2 hours then varies in a wide range, showing improvements in the 4 to 10 hours range. The data indicate that a solution treatment time of ~1 hour is sufficient to achieve maximum strength. The changes in mechanical properties were correlated to changes in microstructure evolution—Mg-Si precipitation, Si particle fragmentation, and microstructure homogenization. Empirical models uniquely relating Si content to UTS and YS are given for T61 heat-treated alloys. 相似文献
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Jung-Jen Allen Cheng Diran Apelian Roger D. Doherty 《Metallurgical and Materials Transactions A》1986,17(11):2049-2062
The rheocasting solidification process has been applied in the production of IN-100 nickel base superalloy. A high vacuum
furnace for rheocasting superalloys was used to rheocast ingots under different processing conditions. Processing variables
which were evaluated include stirring speed, isothermal stirring time, and volume fraction solid during isothermal stirring.
Ingots, furnace cooled at the same rate but without stirring, were also examined for comparison with the rheocast ingots.
A detailed microstructural examination was made of the resultant microstructure both on furnace cooling after stirring and
on reheating to the isothermal stirring temperature followed by water quenching. Rheocasting yielded fine-grained structures,
where the extent of microsegregatiori, the variation in macrostructure, and the solidification-induced porosity were found
to be reduced in comparison to the unstirred ingot. The grain size and nonuniformity in the as-cast ingot were reduced by
increasing the stirring speed, isothermal stirring time, or the volume fraction solid during stirring. The degree of the microsegregation
decreased significantly with increasing volume fraction solid. Grain boundaries, both with and without solute enrichment,
were found in the rosette-like solid particles after rheocasting, lending support to the Vogel-Cantor-Doherty model of rheocasting
based on the formation of grain boundaries by strain-induced recrystallization and by sintering. It is clear from these results
that the microstructure of this superalloy was significantly improved by rheocasting. Improved mechanical properties were
also found and will be reported separately. 相似文献
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Suresh Annavarapu Diran Apelian Alan Lawley 《Metallurgical and Materials Transactions A》1990,21(12):3237-3256
Near-net shape manufacturing (NNSM) of thin steel sections by spray casting eliminates casting as a separate step with attendant
improved microstructures and properties and significant energy savings. The process involves atomization of a stream of liquid
metal and deposition of droplets in the generated spray on a moving substrate at mass flow rates of 0.25 to 2.5 kg/s. In this
paper, NNSM of steel strip by the Osprey spray casting process is investigated by combining numerical simulation and experiments.
Critical input parameters for the computation are quantified utilizing existing state-of-the-art mathematical models and specific
experiments. Numerical computation of the consolidation of the spray at the substrate during manufacture of thin sections
is conducted using bothcontinuum anddiscrete event (“splat solidification”) approaches to predict: (1) variation of strip thickness in the transverse dimension and (2) isotherms
and cooling rates across the strip thickness. Predicted geometries of the strip simulated by the continuum model are in good
agreement with measurements. Predicted isotherms in narrow strip by the continuum approach are in reasonable agreement with
thermocouple measurements for intermediate thicknesses (2 to 5 mm), and the observed microstructure is consistent with predicted
cooling rates. The discrete event model predicts significantly higher cooling rates than the continuum model in the basal
portion of the strip. This is consistent with the observed grain size in thin strip (<l-mm thick) and in the basal portion
of thick strip. Beyond a threshold thickness, however, the discrete event model confirms the formation and persistence of
a partially liquid layer at the growing surface of the deposit with an attendant decrease in the cooling rate. The influence
of critical parameters on “splat solidification” is analyzed and assessed.
DIRAN APELIAN, formerly Howmet Professor of Materials Engineering at Drexel University 相似文献
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Sumanth Shankar Diran Apelian 《JOM Journal of the Minerals, Metals and Materials Society》2002,54(8):47-54
This work provides a comprehensive understanding of the reactions at the ferrous die/molten metal interface in a metal mold
casting operation. The literature has shown that several important factors influence reactions at the ferrous die/molten aluminum
interface, including temperature of the melt, temperature of the die, alloy chemistry of the melt and die, die surface engineering,
topographical features, and coatings. This article discusses the effect of the more critical factors on soldering, based on
the authors’ investigations. Inaddition, based on a mechanistic understanding of the interface reactions between ferrous die
and molten aluminum, recommendations are given for specific processing issues to alleviate soldering during die casting of
aluminum alloys. 相似文献
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Georg Leuenberger Reinhold Ludwig Diran Apelian 《Journal of Nondestructive Evaluation》2002,21(4):111-116
Ongoing research at Worcester Polytechnic Institute (WPI) has recently resulted in the development of an electrostatic multipin instrument capable of testing green-state compacts directly after compaction. By monitoring a steady electric current flow through the sample and recording the voltages over the surface valuable information is gathered, leading to the prediction of the structural health of the green-state parts. Whereas our prior work concentrated on the detection of surface-breaking and subsurface defects, which requires the determination of large differences in material properties over small flaw sizes, the results presented in this paper aim at the density prediction throughout the volume of the sample. This requires the detection of small changes in material properties over large regions. A physical model and a mathematical formulation are reported, which are capable of relating green-state density changes to electric conductivity in the presence of various lubricant concentrations. Preliminary electrostatic measurements of cylindrical compacts have thus far confirmed the theoretical model assumptions, showing that the electric conductivity follows a complex graphical behavior that is determined by the type and concentration of the lubricant. Specifically, the green state conductivity increases as the sample density increases up to values of approximately 6.9 to 7.0 g/cm3. Any further density increase, however, results in a decrease in conductivity. 相似文献
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