Forging of liquid and partially solid Sn-15 Pct Pb and aluminum alloys

Abstract

The possibility of producing simple shaped components from a liquid and partially solid initial charge material in a forging type operation was investigated. Ingots of Sn-15 Pct Pb alloy and aluminum alloys 6061 and A356 were heated to temperatures above the liquidus and in the liquid-solid range. The partially solidified charge materials were previously made in a continuous slurry producer. Sound flange shaped cup parts and unidirectionally solidified cylinders were produced in a 50 ton hydraulic press. Die thermal behavior was experimentally determined from thermocouples located at different distances from the metal-die interface. Measured maximum die temperatures were lower when the initial charge material was partially solid or when applied pressure was reduced. A one dimensional computer heat flow program was developed to simulate heat flow in the cylindrical parts and the steel dies. Correlation of computer predictions and measured temperatures were used to calculate values of the heat transfer coefficients at the metal-die interface prior to and after pressurization. The heat transfer coefficients increase by one order of magnitude or more upon application of 9.1 × 10⁷ Pa pressure. Heat transfer coefficients prior to and after pressurization were 3.4 × 10³ and 3.4 × 10⁴ W.m^-2.K^-1, respectively, for a liquid and 8.4 × 10² and 3.1 × 10⁴ W.m.^-2.K^-1 respectively, for a 0.5 volume fraction solid charge of A356 aluminum alloy.