合金钢缺口试样热预应力增韧机理的研究

Investigation of mechanism of toughness improvement of warm prestressing in notched specimens of alloy steel

用缺口试样进行了一系列不同循环的热预应力 (WPS)试验 ,以研究合金钢热预应力增韧效应的机理 .测量了宏观力学参数 ,对断口和热预应力后卸载试样缺口前的微观特征也进行了观察 .实验结果表明 :产生残余压应力和使缺口钝化张开的WPS循环可以改善低温缺口韧性 .相反 ,产生残余拉应力和使缺口根部锐化闭合的WPS循环使缺口韧性变差 .随着提高WPS载荷 ,越来越多的潜在解理起裂第二相粒子被剥离和钝化成微孔 .

A series of experiments are carried out on notched specimens to investigate the mechanism of toughness improvement of warm prestressing (WPS)of alloy steel. The macro mechanical parameters are measured and the fracture surfaces and the microscopic features in front of notch roots of specimens unloaded after WPS are observed. Experimental results show that warm prestressing cycles which produce compressive residual stress and make the notch root open and blunted can improve notch toughness at low temperatures. Conversely, WPS cycles which produce tensile residual stress and make the notch closed and sharpened will deteriorate notch toughness. With increasing the preload of WPS, more and more particles with potential cleavage nuclei are decohered and blunted to cavities. This effect also can improve notch toughness.