tigation. For component designers the value of YS is a key input for software stress analysis. Complex shaped casting may as a result have a large variation in λ2
, but
may lead to a part design, or alloy selection, which is not effectively optimized, or worse, over predicts a met- ric such as the YS when stress analysis software is used. Thus, for modelling and simulation purposes, the wedge casting may have to be cast and analyzed if alternative al- loys are being considered for implementation.
tensile samples used to generate actual YS data are ex- tracted from limited locations, such as the bulkhead sec- tion (critical one). Most sections of component castings cannot provide tensile samples, such as the head deck, cylinder bore walls, etc. Not having a clear understand- ing of the change in YS for different measured values of λ2
Conclusions
The authors investigated four Al-Si-Cu castings alloys with the aim of establishing improved fatigue performance without design modifications. The wedge casting was investigated and the U328 was found to have the lowest porosity levels.
The component engine block, not having ideal progressive solidification conditions, not only showed a larger porosity drop between the W319 and U328 alloy, but showed a 40% increase in fatigue performance. This however, does not ne- gate the usefulness of the wedge casting as an integral tool in alloy conversion assessment. Test samples cannot be ex- tracted from most locations of the component engine block which may have different YS values needed for adequate
Figure 23. Scanning Electron Microscopy in the Secondary Electron (SEM/SE) mode micrographs showing subsurface pores located within the fractured region.
48 International Journal of Metalcasting/Fall 10
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85