Fig.8. The grain structures under different casting conditions[68](a) convention casting process, grain size: 4560 μm(b) convention casting with grain refiners, grain size: 1230 μm(c) thermally-controlled solidification process, grain size: 3340 μm(d) thermally-controlled solidification with grain refiners, grain size: 126 μm (convention casting: pouring temperature is 1380 ℃, mold temperature is 1290 ℃, withdrawal speed is 0 μm/s; thermally-controlled solidification: pouring temperature is 1380 ℃, mold temperature is 1290 ℃, withdrawal speed is 400 μm/s) |