UNDULATORY SOLID SHELL GROWTH OF ALUMINUM ALLOY 3003 AS A FUNCTION OF THE WAVELENGTH OF A GROOVED MOLD SURFACE TOPOGRAPHY

摘要

The effects of the wavelength of a grooved mold surface topography and casting speed on the early stages of solidification of aluminum alloy 3003 have been experimentally studied. This involved the controlled production of cast shells of AA3003 alloy with an immersion tester and instrumented grooved copper molds. The grooves were 0.232 mm deep with wavelength or spacing between 1 mm and 15 mm. Castings produced with ungrooved mold surface topography and with grooves of 5 mm to 15 mm wavelength exhibited macroscopic undulatory shell growth front. The propensity for undulatory shell growth also increased with increase in casting speed and wavelength of the grooves. There was an apparent relationship between the macro-morphological features (depressions and humps) of the undulatory shell and subsurface microstructure. Undulatory shell growth is provisionally attributed to the irregular thermomechanical distortion of the solidifying shell engendered by spatial variations in the heat extraction profile along the mold-shell interface during solidification.