This page contains a Flash digital edition of a book.
Presentation Alternatives to the Al-Si Eutectic


System in Aluminum Casting Alloys (15-089)


Authors Teodoros Koutsoukis and Makhlouf


Makhlouf, Worcester Polytechnic Insti- tute, Advanced Casting Research Center, Worcester, Mass.


Background


The majority of the traditional aluminum casting alloys are based on the aluminum-silicon eutec- tic system because of its excellent casting characteristics, including good fluidity and resistance to hot tearing. Unfortunately, the solidus in this system does not exceed 1,071F (577C) and the major alloying elements in traditional aluminum casting alloys, e.g., zinc, magnesium, and copper, further depress the al- loy’s liquidus temperature. Moreover, these alloying elements have high diffusivity in the aluminum solid solution and their diffusivity in- creases with increased temperature. Therefore, while casting alloys based on the aluminum-silicon eutectic and traditional strengthening ele- ments have good room temperature strength, their strength is rapidly degraded when they are used at tem- peratures higher than 482F (250C). Furthermore, silicon interacts with aluminum and iron—which is invariably present in commercial aluminum casting alloys—to form harmful intermetallic compounds, such as the β-(Al5


SiFe) phase, which


adversely impacts the alloys’ ductil- ity, or with precipitation strengthen- ing elements. In many applications, stability of


mechanical properties at high tem- perature is the primary need, not high strength at room temperature. In this study, the binary aluminum-nickel and aluminum-iron eutectics, as well as the ternary aluminum-iron-nickel eutectic are considered as alternatives to the aluminum-silicon eutectic for constituting aluminum casting alloys. Te purpose of this investigation is to measure the casting ability (i.e., the tendency to hot tear and the ability


to fill the mold cavity), the room and elevated temperature (662F or 350C) tensile properties (i.e., ultimate tensile strength, yield strength and elonga- tion) of these eutectic compositions, and compare them to their counter- parts for the aluminum-silicon eutec- tic and, when necessary, also to those of commercial grade A390, A206 and 413.0 alloys.


Conclusions Te three alternative eutectic sys-


tems investigated, namely the Al-Ni eutectic, the Al-Fe eutectic and the Al-Ni-Fe eutectic, exhibit very good casting ability and tensile properties at both room temperature and elevated temperature; and in this regard, they compare favorably with the Al-Si eutectic. Among the four eutectics, the Al-Ni eutectic has the highest strength at room temperature, but Ni is significantly more expensive than Si and Fe. Te Al-Fe eutectic has excel-


lent casting ability and is inexpensive compared to the Al-Ni eutectic, but it has the lowest room temperature strength among the four eutectics. Te elevated temperature (662F or 350C) tensile properties of the Al-Ni, Al-Fe and Al-Fe-Ni eutectics are superior to those of the Al-Si eutectic with the 662F (350C) tensile strength of the Al-Ni-Fe eutectic being the highest among all four eutectics. Among the four eutectic systems investigated, the Al-Fe-Ni eutectic is the most thermally stable. The Al-Fe-Ni eutectic combines


characteristics of both the Al-Ni and Al-Fe systems, i.e., good casting ability, good elevated temperature tensile properties, and low cost. Therefore it is the most promis- ing of the eutectic systems for high temperature applications. Te three papers summarized in this


article were presented at the 119th Met- alcasting Congress in Columbus, Ohio.


ALUMIN UM ME L TE RS!


-25 “Hg, S.G.: 2.47


-26 “Hg, S.G.: 2.36


QCD-1 Porosity Measurement System


• Automatic measurement and recording of Specific Gravity / Sample Porosity in 15 seconds.


• Eliminates the need to cut and polish the sample to permit a very subjective estimation of gas level.


T.R.P. Vacuum Tester (True Reduced Pressure)


• Measures the absolute vacuum level, eliminating the need for daily/weekly/monthly calibration of the differential gage used on most RPT units.


• Fully automatic operation to pull the Absolute Vacuum to a target level of (+/- 0.20”Hg), run a timed cycle, and dump the vacuum.


Contact Us Today to learn more! E-mail: dan@qcdesignsinc.comwww.qcdesignsinc.com


Q.C. Designs, Inc. (269) 983-6859 • Fax: (269) 982-0823


May 2015 MODERN CASTING | 33


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76