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Figure 5.57 Successive stages of grain evolution in a low-carbon steel, from its freezing point to room temperature see text for full explanation . again to reduce the ratio to around 1.4, indicating solidification to austenite, and a successful grain refinement with CaCN2. Roberts et al. 1979 confirm that only ferritic material was refinable with titanium additions, and confirm that TiC and TiN have lattices that are good fits with ferrite, but poor fits with austenite. Baliktay and Nickel...
Solidification shrinkage
The molten metal in the furnace occupies considerably more volume than the solidified castings that are eventually produced, giving rise to a number of problems for the founder. There are three quite different contractions to be dealt with when cooling from the liquid state to room temperature, as Figure 7.1 illustrates. Figure 7.1 Schematic illustration of three shrinkage regimes in the liquid luring freezing and in the solid. Figure 7.1 Schematic illustration of three shrinkage regimes in the...
102 Hot isostatic pressing
Coble and Flemings 1971 confirmed that pores, if sufficiently fine, and in a fine-grained matrix, would gradually disappear given a few tens of hours and a temperature high enough for a 'sintering reaction' to occur. They found that the application of modest pressure, about 20 atmosphere, greatly assisted the process. The development of hot isostatic pressing HIPping was the outcome. Much higher pressures were employed, usually nearer 1000 atmospheres, and temperatures as near the melting point...
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Figure 9.13 Relation between the initiators of fatigue cracks and the fatigue life for unfiltered open symbols , filtered solid symbols and unfiltered and HIPped cross and star symbols Al-7Si-0.4Mg alloy castings tested at 240 MPa and R 0.1 Nyahumwa et al. 1998 . were categorized either as young, thin film or older, thicker film, based on the thickness of folds b slip mechanisms indicated by a typical faceted transgranular appearance and c fatigue striations, often called beach marks, denoting...
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10 1 02 1 03 1 0 105 106 107 N cycles Figure 9.11 Fatigue curves for filtered and unfiltered pearlitic ductile irons data from Simmons and Trinkl 1987 and for an aluminium alloy data from Pitcher and Forsyth 982 . cylinder heads is another instance of the importance of the elimination of defects, so as to introduce a long stage I to the fatigue crack propagation. This industrial experience has now been confirmed by a careful laboratory study by Nyahumwa et al. 1998 and 2000 on Al-7Si-0.4Mg...