超塑处理对喷射成形GCr15钢超塑性的影响

研究了超塑处理对喷射成形GCr15钢超塑性的影响，超塑性拉实验结果表明，未经超塑处理的铸态试样，延伸率为119％，经过二次油淬和二次油淬＋高温回火超塑处理的两种试样，延伸率分别为328％和671％，变形温度和应变速率对GCr15钢的超塑性有一定的影响，但材料的微观组织对其超塑性具有决定性作用，超塑处理改变了材料试样的微观组织，导致其超塑性发生变化，经过二次油淬＋高温回火超塑处理后试样具有球化组织，其超塑性最好，未经超塑处理的铸态试样具有珠光体组织，超塑性最差，经过二次油淬超塑处理后试样的组织是马氏体和少量碳体物的混合，其超塑性介于上述两种试样之间，喷射成形工艺使GCr15钢获得均匀细化的稳定组织，这对于细晶超塑性是必要的，超塑处理材料的超塑性得到更大的提高。

INFLUENCE OF SUPERPLASTIC TREATMENT PROCESS ON THE SUPERPLASTICITY IN SPRAY FORMING GCr15 STEEL

The results of superplastic tensile tests showed that the elongations of specimens of the spray forming GCr15 steel without superplastic treatment and of twice oil quenching and twice oil quenching plus high temperature tempering superplastic treatment were 119%, 328% and 671%, respectively. It is known that both Deformation temperature and strain rate have a certain influence on the superplasticity during deformation, but microstructure of the specimen has a determinative effect on its superplasticity.The present work have demonstrated that the differences in the superplasticities of specimens resulted from their different microstructures which were gained by superplastic treatment.The superplasticity of specimen with the spheroidized microstructure obtained by twice oil quenching plus high temperature tempering superplastic treatment was inferior to none. The specimen with pearlitic microstructure without superplastic treatment had the poorest superplasticity, And the superplasticity of the specimen with mixed microstructures, which were composed of martensite and a little carbide, gained by twice oil quenching superplastio treatment was situated between them as mentioned above. With Spray forming technique one can prepare materials with a stable structure of fine grain size and homogeneous distribution of composition. It is just a necessary condition to fine grained superplasticity. The enhancement in superplasticity is exactly realized by selecting appropriate superplastic treatment process.