高强耐热镁合金GW103K近液相线制浆工艺

Preparation of a New High Strength and Heat Resistant GW103K Magnesium Alloy Semi-solid Slurry by Near Liquidus Method

采用近液相线法制备了新型高强耐热镁合金GW103K(Mg-10Gd-3Y-0.6Zr)半固态浆料,并与高于液相线温度浇注锭坯的组织进行对比,同时,考察了近液相线浇注时静置时间和不同铸模浇注时冷却速率对铸造组织的影响。结果表明,近液相线温度浇注所获得的GW103K镁合金半固态组织与高于液相线温度浇注的相比发生了明显的变化,近液相线法浇注有利于含Zr的GW103镁合金晶粒的球化,圆整度也大大提高,但晶粒发生了明显的融合长大;近液相浇注时随静置时间的延长,晶粒变得比较粗大,圆整度显著降低,同时晶界变得比较细,分布在晶界上的金属间化合物明显减少;增加冷却速率有利于组织细化,也促进了球化的趋势。对于新型高强耐热镁合金GW103K,在近液相线温度不需静置浇注至冷却能力较强的铸模中即可获得理想的半固态浆料。

A new type high strength and heat resistant Mg-10Gd-Y-Zr(GW103K)magnesium alloy semi-solid slurry was prepared by the near liquidus casting method,and its microstructure was compared with that prepared by over-liquidus casting method.And the effects of holding time and cooling rate of the mould on the as-cast microstructure of the alloy were investigated in near-liquidus casting method.The results reveal that compared with that prepared by over-liquidus casting,microstructure of the GW103K semi-solid slurry prepared by near-liquidus casting is obviously changed.Near-liquidus casting is beneficial to the spheroidization of grain size in the GW103K containing Zr with obviously increasing in roundness,However,grain size becomes coarse as a result of fusion mechanism.With increasing in holding time,grain size is increased with the great decrease of roundness,while grain boundary is refined due to the reduction of intermetallics distributed along the boundary.With increasing in cooling rate,the grain size in the alloy is refined with the increase of shperoidization.The new type high strength and heat resistant magnesium alloy GW103K slurry with more perfect spheroidized structure can be prepared by near-liquidus casting method by the molten alloy immediately pouring into a high cooling capacity mould at near-liquidus temperature.