ZA27合金蜗轮毛坯的成形性与力学性能

对ZA27蜗轮毛坯进行了金属型铸造、挤压铸造和半固态挤压成形试验,研究了在不同工艺条件下,制件的宏观成形性、微观组织形貌和力学性能。结果发现,金属型铸造蜗轮毛坯组织从齿顶到分度圆,均为细密发达的树枝晶;挤压铸件齿顶无树枝状枝晶,齿根的树枝晶晶臂有碎断现象,分度圆枝晶组织破碎圆整痕迹较为明显;半固态挤压件齿顶晶粒组织细化,分布较为均匀,齿根部呈典型的玫瑰状半固态组织形貌,分度圆为细小的等轴晶粒组织。金属型铸造蜗轮齿型成形困难;挤压铸造制备的蜗轮,外观轮廓清晰,齿形饱满;半固态挤压件成形性更加优良。半固态成形件力学性能高于挤压铸造和金属型铸件。

Formability and Mechanical Properties of the ZA27 Alloy Worm Gear Blanks

Macroscopic formability,microstructure and mechanical properties of the ZA27 alloy worm gear blanks in permanent mold casting,in liquid forging and in semisolid die forging were investigated under various process conditions.The results show that the microstructure of the worm gear in permanent mold casting is fine-developed dendrite from the addendum to the graduated circle.Absence of dendritie in the addendum and broken phenomenon of the dendrite arm in the dedendum of the worm gear in liquid die forging can be observed,and it is obvious that the dendritic structure in the graduated circle is broken and spheroidized.The refined microstructure in the addendum with uniform distribution and rosette structure in the dedendum are presented in semisolid die forging,and the microstructure in the graduated circle exhibits fine equiaxed grain.It is difficult for the tooth profile of worm gear to form by permanent mold casting,and the worm gear has clear outline with plumptooth profile by liquid forging and the formability is more desirable by semisolid die forging.The mechanical properties of the parts by semisolid die forging are superior to those prepared by permanent mold casting and by liquid forging.