钢铁材料及有色合金构件的多段半固态成形工艺研究

目的为了有效抑制半固态成形过程中的液相偏析,改善半固态成形构件微观组织和力学性能的均匀性。方法提出了包括多段流变成形和多段触变成形在内的多段半固态成形工艺。多段半固态成形工艺均由半固态坯/浆料制备、预成形、控温冷却和终成形4个阶段组成,分别在热模拟试验机和机械伺服压机上开展了SKD11工具钢和6061铝合金的半固态触变成形和半固态流变成形试验。结果在初成形阶段,具有较高液相分数的半固态坯/浆料以较高的应变速率初步充填型腔,限制了液相外流的时间和空间;在控温冷却阶段,半固态坯/浆料的液相分数因部分凝固而降低;在终成形阶段,具有较低液相分数的半固态坯/浆料以较低的应变速率完成型腔的充填,由于固相晶粒在此阶段发生塑性变形而提高了成形构件的力学性能。结论获得了组织均匀性较好的钢铁材料和有色合金构件,验证了多段半固态成形工艺的可行性。

Multi-stage Semisolid Forming of Ferrous and Non-ferrous Components

To effectively inhibited the occurrence of liquid segregation during semisolid forming and improve the homogeneities of microstructure and mechanical properties of semisolid formed components, multi-stage semisolid forming processes including multi-stage thixoforming and multi-stage rheoforming were proposed in this study. Multi-stage semisolid forming was composed of preparation of semisolid slurry, first forming, controlled cooling, and secondary forming. Multi-stage thixoforming of SKD11 tool steel and rheoforming of 6061 Al alloy were conducted on a Thermecmastor-Z compression machine and a mechanical servo press machine, respectively. In the first forming stage, the cavity was filled with semisolid slurry of high liquid fraction at high strain rate. The time and space for out-flow of liquid phase was restrict. In the controlled cooling stage, the liquid fraction of semisolid slurry was decreased by partial solidification. In the secondary forming stage, the cavity was filled with semisolid slurry of low liquid fraction at low strain rate. Plastic deformation of solid particles resulted in excellent mechanical properties of component. The feasibility of multi-stage semisolid forming processes on manufacturing ferrous and non-ferrous alloys components with homogenous microstructure and mechanical properties is verified.