烘烤硬化及Cottrell气团形成机制的内耗研究
发布时间：2018-11-22 12:43
【摘要】：针对低碳钢的烘烤硬化和Cottrell气团的形成机制进行了研究,探索了应变时效初期Cottrell气团的形成、较长时间时效后的碳化物沉淀以及热处理态的烘烤硬化性能,分别测量了其BH值、应力-应变曲线和内耗-温度谱,并从原子层面揭示其烘烤硬化机理。主要研究结果如下:(1)当预应变量为2%、烘烤温度为170℃时,随着烘烤时间的增加BH值与SKK峰的峰高有线性关系,他们的关系可以表示为BH=17119*hSKK-33;低碳钢在200min烘烤时间内的时效硬化机制主要是Cottrell气团强化,位错钉扎点即气团数量的增加是屈服强度增加的主要原因,碳原子在位错的浓度随时效时间变化不大。(2)多种应变时效工艺下,预变形由2%增加到5%,BH值降低,SKK峰峰高增加;在170℃时效,预变形由5%增加到16%,BH值降低,屈服点延伸率增加。(3)随着热处理保温时间延长,平均晶粒尺寸不断增大,晶粒的不均匀性逐渐增加,烘烤硬化值逐渐减小。与原始样品相比,热处理样品的BH值较高。随着热处理保温时间延长,间隙碳原子含量下降,SKK峰逐渐升高,间隙碳原子和Cottrell气团共同影响了BH值的变化。烘烤前后相比较,Snoek峰高降低,SKK峰高升高。(4)与原始样品相比,热处理样品的BH值较高;随着时效时间延长,间隙碳原子含量下降,SKK峰逐渐升高;热处理后的样品,在时效过程中,碳原子向晶界和位错扩散的同时大量脱溶形成细小碳化物;在100 min时效时间内出现的p2峰、麻点和强度的下降与过饱和碳原子的脱溶过程有关;过饱和碳原子的脱溶造成软化,使BH值下降致负值。
[Abstract]:The mechanism of baking hardening and Cottrell air mass formation of low carbon steel was studied. The formation of Cottrell air mass at the initial stage of strain aging, the carbide precipitation after long aging and the baking hardening property of heat treatment state were investigated. The BH values were measured respectively. The stress-strain curve and internal friction temperature spectrum are also studied, and the mechanism of bake hardening is revealed at atomic level. The main results are as follows: (1) when the prestrain is 2 and the baking temperature is 170 鈩，
本文编号：2349407
[Abstract]:The mechanism of baking hardening and Cottrell air mass formation of low carbon steel was studied. The formation of Cottrell air mass at the initial stage of strain aging, the carbide precipitation after long aging and the baking hardening property of heat treatment state were investigated. The BH values were measured respectively. The stress-strain curve and internal friction temperature spectrum are also studied, and the mechanism of bake hardening is revealed at atomic level. The main results are as follows: (1) when the prestrain is 2 and the baking temperature is 170 鈩，
本文编号：2349407
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