无模拉拔成形连续柱状晶BFe10-1-1合金管材的残余应力

在拉拔温度850℃、拉拔速度0.7mm/s、进料速度0.5mm/s的条件下,对连续柱状晶组织BFe10-1-1合金管材进行无模拉拔成形,采用X射线法测定管材的残余应力,采用TEM进行微观组织分析,探讨了残余应力产生的机理。结果表明,沿着拉拔方向,无模拉拔合金管材的变形区外表面残余应力分布呈先升高后降低的趋势;已变形区残余应力值较为均匀;各点残余应力均为压应力,最大值为135MPa。无模拉拔成形过程中,连续柱状晶组织BFe10-1-1合金管材的晶界变得曲折,晶界周围出现不同密度的位错塞积,变形区沿拉拔方向的位错密度呈先增大再减小的趋势,这一趋势是导致产生不同程度残余应力的根本原因。

Study of residual stress of a BFe10-1-1 alloy tube with continuous columnar grains after dieless drawing

Residual stress of a BFe10-1-1 alloy tube with continuous columnar grains was measured after dieless drawing by X-ray method.The microstructure of the tube was observed by means of TEM.The dieless drawing of the tubes was performed in the temperature of 850℃ at the drawing speed of 0.7mm·s-1 and the feed speed of 0.5mm·s-1.The mechanism of residual stress was investigated.The results indicated that the residual stress along the drawing direction at deformation zone on the outer surface of the tube increased at first,and then decreased.And the residual stress distribution at deformation zone was relatively uniform.All residual stress was compressive stress,with the maximum of 135MPa.The straight grain boundary of columnar grains in the tube became zigzag after dieless drawing.Dislocations tended to pile up at the zones adjacent to grain boundary with different densities.The essential reason of the different degrees of residual stresses was that the dislocation density firstly increased and then decreased.