ZK60-2Ca鎂合金半固態(tài)坯料的部分重熔Partial remelting of semi-solid metal ingots of ZK60-2Ca magnesium alloy

半固態(tài)金屬坯料部分重熔是半固態(tài)金屬觸變成形工藝的重要技術(shù)環(huán)節(jié)，為了使坯料獲得既細(xì)小又圓整的晶粒組織，對近液相線鑄造ZK60鎂合金半固態(tài)坯料進(jìn)行部分重熔，通過改變重熔溫度和保溫時間來研究其微觀組織的演化規(guī)律。結(jié)果表明：適當(dāng)控制加熱溫度和保溫時間，坯料部分重熔時可獲良好的觸變結(jié)構(gòu)。石墨模澆注時，在600~605 ℃、保溫10~15 min時可獲得較理想的觸變結(jié)構(gòu)，平均晶粒尺寸達(dá)30.5 μm，圓度達(dá)1.5；水冷銅模澆注時，可得出相同的結(jié)論，其晶粒平均直徑為31.8 μm，圓度達(dá)1.6。且坯料近液相線鑄造時的冷卻速率對部分重熔的進(jìn)程也產(chǎn)生影響，適當(dāng)降低鑄造冷卻速率，即采用石墨模能提高二次重熔組織的均勻性和穩(wěn)定性。

Partial remelting is the important part of semi-solid metal (SSM) ingots forming technology. In order to obtain small and round grain organization microstructure, the microstructure evolution of ZK60 magnesium alloy SSM ingots obtained by near-liquidus casting were partially remelted, and the microstructure evolution would be investigated by controlling remelting temperature and holding time. The results indicate that good thixotropic microstructure will be obtained by controlling remelting temperature and holding time suitably. Using the graphite mould, optimizing thixotropic microstructure can be obtained at 600-605 ℃ for 10-15 min, the average diameter of grain is 30.5 μm and the roundness is 1.5. With the water-cooled copper mould, the conclusion is the same, the average grain diameter is 31.8 μm and the roundness is 1.6. Meanwhile, the cooling rates during casting also affect the partial remelting progress, reducing the cooling rate properly, the graphite mould can improve the uniformity and stability of the partial remelting microstructure.

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