Zr基非晶合金精密直齿轮超塑性成形试验研究

SUPER-PLASTIC DIE FORGING OF FINEPRECISION SPUR GEAR OF Zr-BASEDBULK METALLIC GLASS

具有多种优异性能的大块非晶合金是近年来材料领域的重要研究成果之一。由于非晶合金在过冷区域表现出良好的超塑性性能,因而有望通过塑性加工的方法来获得非晶质的复杂结构精细零部件。以直径为5 mm的zr41.25Ti13.75Ni10Cu12.5Be22.5非晶合金棒材为试验材料,采用自行设计的专用真空炉和精密模锻装置,对带轮毂的精密直齿轮(节圆直径6 mm,齿数24,模数0.25 mm)进行了超塑性成形试验。分析对比了上芯杆直接冲孔成形、下芯杆直接冲孔成形和两阶段冲孔成形三种不同工艺的成形结果。结果表明,在其他工艺参数相同的条件下,两阶段成形工艺比其余两种工艺具有更低的成形压力和较小的内孔偏心度。选用两阶段成形工艺和合理的模具结构,制备出了具有良好尺寸精度和表面粗糙度的精密齿轮。经x射线衍射分析表明,所成形的齿轮没有发生明显晶化现象,从而较好地保持了大块非晶合金材料的各种优异性能。

Bulk metallic glass (BMG) is one of the important research results of material science in recent years, which has many excellent properties compared with other metallic engineering materials. Because of the excellent super-plasticity in super-cooled liquid region of BMG, it is very hopeful to fabricate precision amorphous metallic parts with complicated configuration through plastic working processes. Using Zr41.25Ti13.75Ni10Cu12.5Be22.5 bulk metallic glass rods of 5 mm diameter, fine spur gear with boss (pitch diameter 6 mm, number of gear teeth 24, modulus 0.25 mm) is fabricated with super-plastic die-forging method under vacuum condition. The forming results of different processes such as hole-forming by upper-mandrel, hole-forming by bottom-mandrel and two-stage forming are analyzed. The results show that the two-stage hole-forming process has lower forming pressure and decentralization level of inner hole. The fine spur gear with good size-precision and surface-roughness is obtained through two-stage hole-forming process scheme and reasonable die structure design. XRD shows that the fabricated parts have no obvious crystallization, the excellent properties of as-cast Zr41.25Ti13.75Ni10Cu12.5Be22.5 bulk metallic glass being kept.