in direct contact with the liquid alloy, removing the latent heat of solidifi ca- tion with high cooling rates. As the ablation solvent progres-
sively moves from one end of the casting to the other, it results in rapid unidirectional solidifi cation. Heavy sections where solidifi cation is slower
typically show higher cooling rates when ablated. T ese characteristics of ablation are expected to lead to a more refi ned microstructure, especially in the case of the interdendritic eutectic, and a uniform distribution of rein- forcement particles. A comparison of relative properties of monolithic A356
COMMERCIAL ABLATION CASTINGS The ablation sand casting process is not reserved to metal matrix com-
posites. The process already has been used successfully in commercial appli- cations, boosting the performance of standard casting alloys, such as A356, and enabling the consistent production of emerging alloys, such as B206. —by MCDP Staff
Rear Motorcycle Frame
Material: A356 aluminum with T6 heat treat.
Weight: 4.9 lbs. Dimensions: 10 x 8 x 6 in.
• The aluminum part achieved enhanced mechanical properties in thin sections through the ablation process.
• The part saved weight and cost by incorporating the motorcycle’s shock mount location.
alloys produced via sand, permanent mold, squeeze and ablation casting are shown in Table 1. Researchers have compared con-
ventionally cast hybrid aluminum- silicon-carbide graphite compos- ites, known as 10S4G, with those produced via ablation to determine the effect each method has on the matrix microstructure and disper- sion of the reinforcement in the composite, as well as the resulting mechanical properties. Examination of the microstructures
of the conventional casting and ablated component revealed the presence of silicon carbide and graphite particles at cell or dendrite boundaries, which is evidence both the particulate rein- forcements were pushed by growing aluminum dendrites into the solute- rich fi nal freezing zones. T e apparent increase in the volume percentage of reinforcement in the ablated sample likely was due to the increased solidi- fi cation rate and decreased fl otation or
Table 2. Properties of the Ablated Component and Conventional Casting
# 1
2 3 4 5 6 7 8 9
Rear Swing Arm Material: B206
aluminum.
Weight: 7 lbs. Dimensions:
26 x 10.25 x 6 in.
• The motorcycle casting features 0.079-in. wall thickness and extensive internal coring. Although prone to hot tears and poros- ity, the B206 alloy in this case achieved grade level 1 x-ray for porosity and inclusions.
• The casting was filled from one end and gated into the wheel axle. No feeders were used in any other area in order to maintain the fin- ish’s cosmetic quality.
38 | METAL CASTING DESIGN & PURCHASING | Jan/Feb 2012 10 Mean
Conventional Casting Tensile
% Elongation
30.6 0.35 30.7 0.35 30.3 0.25 31.2 0.4 31.2 0.45 34.1 0.45 32.5 0.4 33.2 0.4 30
0.35 31.2 0.4 31.5 0.38%
Standard Deviation 1.34 0.06 Ablated Component
# 1
2 3 4 5 6 7 8
Mean
Tensile % Elongation 38.4 0.35 41
0.4
31.6 0.3 37
0.3
33.2 0.3 35.6 0.3
36.1 0.33% Standard Deviation 2.91 0.05 0.25
35.7 0.4 36
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