solidification. Heavy sections where solidification is slower typically show higher cooling rates when ablated. Tese characteristics of ablation are expected to lead to a more refined microstructure, especially in the case of the interden- dritic eutectic, and a uniform distribution of reinforcement particles. A comparison of relative properties of monolithic A356 alloys produced via sand, permanent mold, squeeze and ablation casting are shown in Table 1. In the study, hybrid aluminum-silicon-carbide graphite


composites, known as 10S4G, were conventionally cast and produced via ablation to study the effect each method has on the matrix microstructure and dispersion of the reinforcement in the composite, as well as the resulting mechanical properties.


Ablation Put to the Test


Te study was conducted with an 20.32 x 40.64-cm plate-shaped pattern, suitable for both conventional sand casting and ablation. Te section thickness of the plate casting is 6.35 cm on the left and 3.81 cm on the right. Te total casting weight was 11.6 kg. Te same riser and gating system, which was designed with the aid of solidification modeling software for the conven- tional sand process, was used for both molds. It is possible the increased cooling rates and thermal gradients of the ablation process would require changes in the gating/risering. Tis would be a subject for future testing. Te overall dimensions of the mold for the conventional


cast and ablation component were the same, but the cope por- tion of the mold for the ablation process included the following modifications: 1. Approximately 15.24 cm of sand was removed directly above the casting to increase the rate of ablation in that location.


2. A channel was cut at the edge of the cope to allow water to drain from the mold cavity.


Both types of castings were solutionized at 538C for 12


hours, followed by hot quenching at 60C, and aged at 155C for five hours.


Ablation Results Promising 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 that both the particulate reinforcements were pushed by growing aluminum dendrites into the solute- rich final freezing zones. Te apparent increase in the volume percentage of reinforcement in the ablated sample likely was due to the increased solidification rate and decreased flotation or settling of the reinforcement (Fig. 2). Te ablated sample’s microstructure was more cellular, meaning reinforcement par-


消融结果好


通过观察传统铸件与消融铸件的微观组织发现，在 晶粒内部或枝晶边界上均存在碳化硅和石墨颗粒 。 这表明，两种铸件的强化颗粒均受到生长的铝枝晶将 其推向溶质富集的最终凝固区域。消融试样中的强化 相体积分数明显更大，应该是由于更快的冷却速度、 较小的浮力与较小的强化相的沉淀（见图2）。消融 铸造试样的微观组织像一种蜂窝结构，意味着强化相 颗粒被晶界形成的网所困住，增加了局部强化物的浓


Table 1. Mechanical Properties of A356 Alloy Aluminum Cast in Various Methods 表1 不同方法生产的A356铝合金铸件的机械性能


Property 性能


Ultimate Tensile Strength MPa (ksi) 拉伸强度（MPa） 228 (33) Yield Strength MPa (ksi) 屈服强度（MPa） % Elongation 延伸率


179 (26) 3.5


Sand 砂子 Permanent Mold 金属型 Squeeze Cast 挤压铸造 Ablation 消融铸造 262 (38) 207 (30) 4


312 (45) 243 (35) 11.0


54 | FOUNDRY-PLANET.COM | MODERN CASTING | CHINA FOUNDRY ASSOCIATION Spring 2012


325 (47) 261 (38) 12.5


面区域冷却速度明显加快。消融法的这些特点会带来更 细的晶粒，跨枝晶的共晶的细化尤为明显，这还会带来 强化颗粒的均匀分布。表1为砂型铸造、金属型铸造、挤 压铸造与消融铸造生产的单一A356合金的性能对比。 本研究采用传统铸造方法与消融铸造法生产名为 10S4G的铝-硅化碳-石墨复合材料，以研究每种方法对 微观组织、强化相的分布以及最终机械性能的影响。


消融铸造法的测试


研究采用一个8 x 16-英寸. (20.32 x 40.64cm)的板 形模样，该模样适用于传统砂型铸造和消融铸造法。左 侧厚2.5 英寸(6.35 cm)，右侧厚1.5 英寸(3.81 cm)。铸 件总重25.6 磅(11.6 kg)。


两种砂型使用了同样的冒口和浇道，冒口和浇道是借 助于传统砂型铸造的辅助软件设计的。或许消融铸造法 带来的更快的冷却速率和更大的温度梯度需要对冒口和 浇道做一些改动，这是后续试验的议题之一。 传统砂型铸造与消融铸造的砂型大体尺寸相似，但是 消融铸造砂型的上箱部分包含了以下的改动： 去除铸件上方约6 英寸 (15.24 cm)厚的砂子，以加快 相应区域的消融速度。


上箱边缘开槽，以方便铸型排水。


两种铸件均在538 °C下固溶处理12小时，然后60°C 快速淬火，最后在155°C下时效处理5小时。


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