冷拉拔珠光體鋼絲的力學(xué)性能各向異性研究

冷拉拔珠光體鋼絲的力學(xué)性能各向異性研究STUDY ON ANISOTROPIC MECHANICAL PROPERTIES OF COLD DRAWN PEARLITIC STEEL WIRE

利用拉伸試驗(yàn)機(jī)、SEM、TEM研究了鋼絲在冷拉拔形變過(guò)程中鋼絲力學(xué)性能的各向異性。結(jié)果表明，隨著鋼絲應(yīng)變量的增加，鋼絲各向抗拉強(qiáng)度的差異逐漸明顯。其中，平行方向（平行于拉伸軸方向）、45°方向（與拉伸軸呈45°方向）符合應(yīng)變強(qiáng)化規(guī)律；垂直方向（垂直于拉伸軸方向）的抗拉強(qiáng)度穩(wěn)定在1350MPa附近。原始盤(pán)條（ε=0）中，各向強(qiáng)度相近；形變鋼絲中，平行方向抗拉強(qiáng)度最高，垂直方向抗拉強(qiáng)度最低。原始盤(pán)條中，各向均發(fā)生穿晶斷裂；形變鋼絲中，平行方向發(fā)生微孔聚集型斷裂，45°方向和垂直方向發(fā)生穿晶斷裂或沿晶斷裂。在TEM下觀察拉伸斷裂樣品后發(fā)現(xiàn)，平行方向上，位錯(cuò)均勻分布在鐵素體片層中，各片層協(xié)調(diào)形變；垂直方向上，位錯(cuò)在鐵素體/滲碳體界面處塞積纏結(jié)，產(chǎn)生應(yīng)力集中直至斷裂。表現(xiàn)出明顯的各向異性。

The anisotropic mechanical properties of cold drawn pearlitic steel wires were investigated by tensile test, scanning electron microscopy(SEM), transmission electron microscopy(TEM). Results indicated that the distinctions of tensile strength between three directions( parallel to the tensile axis, inclined to the tensile axis(45°), vertical to the tensile axis) were amplified with increasing strain. The obvious effect of strain hardening was observed in parallel and inclined directions while the vertical direction remained strength stability in 1350MPa. When ε=0, the tensile strength was found isotropic and the fracture mode was transgranular fracture; As strain increasing, the tensile strength reached peaks in parallel direction and valleys in vertical direction and the fracture modes of inclined and vertical directions remained transgranular or intergranular fracture while the fracture mode of parallel direction was converted into microvoid accumulation fracture. In TEM, the phenomenon was discovered that due to non-homogeneous distribution in vertical direction, dislocations piled up at the boundaries resulting in stress concentration. On the contrary, the dislocations were uniformly distributed which led to homogeneous transformation in parallel direction.

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