<正> 一般认为亚共析钢中魏氏组织降低机械性能,尤其是不利于冲击韧性。近年来研究结果则认为魏氏组织可以提高机械性能,也有人认为具有魏氏组织的亚共析钢,由于冷却速度快,增加了珠光体量,细化了铁素体晶粒,从而抵销了针状铁素体的不良影响。另一些人指出切变机制使针状铁素体中有较高密度的位错和较细的亚结构,提高了钢的机械性能。本文根据对裂纹扩展行为的观察,探讨铁素体影响钢的机械性能的原因。 本实验采用25铸钢作试样,其化学成分(wt-％)为:C 0.28,Si 0.37,Mn 0.61,S
The effect of acicular ferrite in Widmanstatten structure on the mechanical properties of subeutectoid steel was studied. The results show that the substrueture of acicular ferrite consists of subgrains. The subgrain boundary is surrounded with dislocation tangles. The interior of subgrain is evenly distributed with the movable dislocations which are higher in density than that in cubic ferrite. The superior strength and better toughness are then obtained. It is revealed under direct observation that the cracks propagate to meet with obstacles of acicular ferrite and to change their direction forward even through or around it. Thus, it seems to be believed that the acieular ferrite in Widmanstatten structure is benefit to improve the mechanical properties of subeutectoid steel.
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