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对D6A钢热轧板进行了两相区轧制及退火处理,获得超细晶D6A合金钢样品,微观结构特征为纳米尺寸的球粒状渗碳体弥散分布于亚微米尺寸的铁素体组织中。实验结果表明:随着退火温度由550℃升高至650℃,铁素体晶粒被拉长现象逐渐减弱直至消失,晶粒尺寸呈现先减小后增大的趋势,在550℃时达到最小尺寸400nm;同时渗碳体尺寸逐渐由70增加至140nm,其质量分数分数由9.6%降低至3.6%;随着退火温度升高,实验钢沿α和γ取向线分布的{112}<110>、{111}<112>和{001}<110>织构强度逐渐减弱,600℃退火后消失,{110}<001>与{112}<111>织构逐渐增强,硬度随退火温度升高由472HV逐渐减小至423HV。细晶强化、纳米尺寸渗碳体的析出强化,以及织构强化的共同作用是超细晶D6A钢的主要强化机制。
D6A steel hot-rolled sheet was subjected to two-phase rolling and annealing treatment to obtain ultrafine-grained D6A alloy steel samples. The microstructure was characterized by nanometer-sized spheroidal cementite dispersedly distributed in submicron-sized ferrite . The experimental results show that as the annealing temperature increases from 550 ℃ to 650 ℃, the ferrite grains are gradually weakened and disappear until they disappear, the grain size first decreases and then increases, reaching the minimum at 550 ℃ The size of the cementite gradually increases from 70 to 140 nm, and the mass fraction of the cementite decreases from 9.6% to 3.6%. With the annealing temperature increasing, {112} <110> The textures of {111} <112> and {001} <110> gradually weakened and disappeared after annealed at 600 ℃. The texture of {110} <001> and {112} <111> From 472HV gradually reduced to 423HV. The main strengthening mechanism of the ultrafine-grained D6A steel is the fine grain strengthening, precipitation strengthening of nano-size cementite, and the combined effect of texture strengthening.