船用螺旋桨材料镍铝青铜的热处理强化

Heat treatment strengthening of nickel-aluminum bronze alloy for marine propeller

采用OM、SEM、EDS、拉伸测试、疲劳裂纹扩展测试、电化学腐蚀测试等研究退火、正火和固溶时效处理对镍铝青铜合金的微观结构、力学性能以及电化学腐蚀行为的影响。结果表明:675℃退火可以消除β′相,显著提高材料的塑性和耐蚀性,但强度稍微降低。固溶时效处理试样强度最高(812 MPa),但伸长率只有2.9%,且腐蚀阻抗最低。适当地正火处理可以提高材料的综合力学性能,同时不降低材料的耐蚀性能。镍铝青铜在空气中的疲劳裂纹扩展速率由高至低的顺序依次为铸态、固溶时效态、正火态。铸态试样的疲劳裂纹主要沿着α相和κⅢ相界面扩展,正火态试样的裂纹一般穿越α晶粒扩展,而固溶时效试样的裂纹既在α相内又在α相和κ相的界面间扩展。

Abstract：The effect of heat treatment on the microstructure and mechanical properties, as well as the electrochemical corrosion behavior of nickel-aluminum bronze alloy was investigated by OM, SEM, EDS, tensile, fatigue crack growth and electrochemical corrosion tests. The heat treatment processes include annealing, normalizing, and aging. The results show that annealing at 675 ℃ could eliminate the β′ phase, which remarkably improves the plasticity and corrosion resistance of the alloy, while its strength degrades slightly. The aged sample demonstrates the highest tensile strength （812 MPa）, but its elongation is only 2.9%, and the corrosion resistance diminishes greatly. The experimental alloy normalized properly could possess good combinations of strength and toughness, and its noncorrodibility keeps good. Fatigue cracks in as-cast sample prefer to propagate through α and κ phase interface. However, the fatigue cracks in normalized alloy mainly propagate through the ductile α grain, and have the lowest crack growth rate. For the aged sample, crack extends through α and κ interface, as well as in α grain.