Abstract
The microstructure and mechanical properties are characterized in a cast, hypoeutectic Al-5.5Ca (wt.%) alloy containing >20 vol% of a micron-scale, eutectic Al4Ca network. The Al4Ca phase, which is monoclinic (C 2/m) at room temperature, undergoes a gradual transformation between 50 and 100 °C to a tetragonal (I 4/mmm) phase. The microhardness of hypoeutectic and eutectic regions is measured as a function of aging time (up to 3 months) at 400 °C and compared to binary, eutectic Al-10Ce, Al-6Ni, and Al-12.6Si alloys: among these cast, binary eutectic alloys, the eutectic Al-Ca regions exhibit the highest specific (density-compensated) microhardness at all aging times, due to the high coarsening resistance and very low density (2.33 g/cm3) of the Al4Ca phase. Compressive creep experiments are performed at 300 °C on the hypoeutectic Al-5.5Ca alloy and compared to hypoeutectic Al-7Ce alloys. The creep resistance of the Al-5.5Ca alloy is somewhat lower than that of the Al-7Ce alloy, despite the much higher volume fraction of intermetallic phases (22 vs. 7 vol%, respectively); however, when considering specific stresses, the creep resistance is the same. The strengthening contributions during creep of the Al4Ca and Al11Ce3 phases are discussed in terms of load transfer and inhibition of dislocation motion, and further opportunities for improvement of high-temperature mechanical properties in eutectic Al-Ca based alloys are identified.
| Original language | English |
|---|---|
| Article number | 148758 |
| Journal | Materials Science and Engineering: A |
| Volume | 943 |
| DOIs | |
| State | Published - Oct 2025 |
Funding
This research was funded by DEVCOM Army Research Laboratory (ARL) and was accomplished under the award W911NF-21-2-0199 and W911NF-20-2-0292. The authors thank Dr. Jon-Erik Mogonye (ARL) for helpful discussions, and Dr. Sumit Kewelramani (Northwestern University) for experimental support in x-ray diffraction. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Laboratory of the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein. This work made use of the MatCI facility which receives support from the MRSEC Program (NSF DMR-2308691) of the Materials Research Center at Northwestern. The work also made use of the EPIC facility of Northwestern University's NUANCE center, which has received support from the ShyNE Resource (NSF ECCS-2025633), the IIN, and Northwestern's MRSEC program (NSF DMR-2308691). This work made use of the Jerome B.Cohen X-Ray Diffraction Facility supported by the MRSEC program of the National Science Foundation (DMR-2308691) at the Materials Research Center of Northwestern University and the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-202563). This work made use of the MatCI facility which receives support from the MRSEC Program ( NSF DMR-2308691 ) of the Materials Research Center at Northwestern. The work also made use of the EPIC facility of Northwestern University's NUANCE center, which has received support from the ShyNE Resource ( NSF ECCS-2025633 ), the IIN, and Northwestern's MRSEC program ( NSF DMR-2308691 ). This work made use of the Jerome B.Cohen X-Ray Diffraction Facility supported by the MRSEC program of the National Science Foundation ( DMR-2308691 ) at the Materials Research Center of Northwestern University and the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource ( NSF ECCS-202563 ). This research was funded by DEVCOM Army Research Laboratory ( ARL ) and was accomplished under the award W911NF-21-2-0199 and W911NF-20-2-0292. The authors thank Dr. Jon-Erik Mogonye (ARL) for helpful discussions, and Dr. Sumit Kewelramani ( Northwestern University ) for experimental support in x-ray diffraction. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Laboratory of the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein.