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研究了固溶和冷却处理对Mg-2Dy-0.5Ni(摩尔分数,%)合金中的长程堆垛有序(LPSO)相形貌及析出硬化行为的影响。铸态合金组织主要包括α-Mg相、分布在枝晶间具有LPSO结构的竹尖状Mg_(12)DyNi相和少量立方体状的Dy相。在565℃固溶处理12 h及随后不同的冷却过程中,点状、块状、细薄片状和棒状的LPSO相分别在基体中析出。在连续冷却(空冷和炉冷)的条件下,细薄片状的LPSO相逐渐在晶粒内部析出;随着冷却时间的延长,其体积分数亦增加,且块状的LPSO相发生粗化。在不连续冷却(炉冷到415℃+空冷和炉冷到265℃+空冷)条件下,点状LPSO相生长成棒状相,降低了合金的冷却硬化作用。
The effects of solution treatment and cooling treatment on the morphology and precipitation hardening behavior of LPSO in Mg-2Dy-0.5Ni (mol fraction) alloys were investigated. The as-cast alloy mainly consists of α-Mg phase, bamboo spinel Mg 12 DyNi phase with LPSO structure distributed in the dendrite and a small amount of cubic Dy phase. During the solution treatment at 565 ℃ for 12 h and subsequent cooling, point-like, massive, flaky and rod-like LPSO phases were precipitated in the matrix respectively. Under the conditions of continuous cooling (air cooling and furnace cooling), the flaky LPSO phase precipitates inside the grain gradually; as the cooling time prolongs, the volume fraction increases, and the massive LPSO phase coarsens. Under discontinuous cooling (furnace cooling to 415 ℃ + air cooling and furnace cooling to 265 ℃ + air cooling), the point-like LPSO phase grows into a rod-like phase, reducing the cooling and hardening effect of the alloy.