The effect of Cu-riched clusters on strength and impact toughness in a tempered Cu-bearing high-strength low-alloy (HSLA) steel is investigated. With increasing the tempering temperature, it is found that the yield strength increases firstly, achieving the maximum value (~ 1053 MPa) at the tempering temperature of 450 °C, and then decreases significantly with the rise of tempering temperature. The tempering temperature-dependent yield strength is closely related to the precipitation of Cu-riched clusters. When tempering at 450 °C, the peak strength will be reached as the nanoscale Cu-riched clusters with small size and high number density will cause a strong precipitation strengthening (~ 492 MPa) due to the dislocation shearing mechanism. However, the Cu-riched clusters will coarsen with further increasing tempering temperature, resulting in obvious decrement of yield strength owing to the dislocation bypassing mechanism. Compared with the yield strength, the variation in impact energy displays an inverse tendency and the impact energy is only 7 J for the sample tempered at 450 °C. The fracture mode can be well explained by the competition between the cleavage fracture strength (σ_F) and “yield strength” (σ_Y). Although transgranular cleavage fracture can be found in samples tempered at 450 and 550 °C, the crack propagation along the lath boundaries is prevented in the sample tempered at 550 °C. The reason is that the number density of Cu-riched clusters at lath boundaries decreases and the segregation of Mo element at the lath boundaries is induced, which will increase the bonding energy.

研究了富铜簇对回火含铜高强度低合金 (HSLA) 钢的强度和冲击韧性的影响。随着回火温度的升高，屈服强度先增加，在回火温度为450℃时达到最大值（~1053 MPa），然后随着回火温度的升高而显着降低。回火温度依赖的屈服强度与富铜簇的析出密切相关。当在 450 °C 回火时，由于位错剪切机制，小尺寸和高数量密度的纳米级富铜簇将导致强烈的沉淀强化（~492 MPa），将达到峰值强度。然而，随着回火温度的进一步升高，富铜簇会变粗，由于位错绕过机制，导致屈服强度明显下降。与屈服强度相比，冲击能的变化呈现出相反的趋势，450℃回火的样品的冲击能仅为7J。断裂模式可以通过解理断裂强度之间的竞争来很好地解释（σ _F ) 和“屈服强度” ( σ _Y )。尽管在 450 和 550 °C 回火的样品中可以发现穿晶解理断裂，但在 550 °C 回火的样品中，裂纹沿板条边界的扩展被阻止。原因是板条边界富Cu簇的数量密度降低，引起Mo元素在板条边界偏析，增加了键能。