This study takes the commercial JG4246A cast Ni3Al-based superalloy as the research object, under the conditions of preheating the mold shell at 1020 °C and a pouring temperature of 1520 °C, characteristic simulation castings were poured. The microstructure and room temperature mechanical properties of different modulus sections of the castings were systematically investigated. It was found that, except for the edge towards the middle section of the larger modulus, the cooling rates at the edge were greater than those at the middle sections. The cooling rate was the fastest at the upper-right corner section (referring to the castings position during pouring, the same below), and the grain is the finest (approximately 0.46 mm), with the highest strength (tensile strength approximately 698 MPa, yield strength approximately 581 MPa), while the cooling rate at the lower-middle section was the slowest, and the grain was the largest (approximately 1.55 mm), with the lowest strength (tensile strength approximately 612.5 MPa, yield strength approximately t 524.5 MPa); the difference in grain size between the two is nearly 237%. The MC carbides at the lower-edge middle section have the smallest size (approximately 3.0 μm) and the elongation rate in this area is the highest (approximately 8.7%), while the MC carbides at the lower-middle section have the largest size (approximately 5.8 μm) and the elongation rate in this area is the lowest (approximately 4.9%); the size difference in the MC carbides between two is nearly 94%. This study clarifies the quantitative correlation between cooling rate, microstructure and properties, providing clear guidelines for optimizing the casting process of high-temperature alloys and subsequent studies on the uniformity of microstructure.
Jiang et al. (Fri,) studied this question.