退火处理对拉拔态B10白铜管材组织和腐蚀行为的影响

Effect of annealing treatment on microstructure and corrosion behavior of as-drawn B10 cupronickel pipes

对取自工程试制的大口径B10白铜管坯进行晶界工程处理:经21%冷扩径拉拔变形后进行成品退火,随后空冷。采用EBSD、SEM、EDS、XPS和失重法研究不同退火温度对拉拔态B10白铜管材晶界特征分布和腐蚀行为的影响。研究结果表明:高温再结晶退火有助于优化拉拔态B10白铜管材的晶界特征分布和提高耐蚀性能。B10白铜管冷拔变形21%,在720℃退火10 min时,低ΣCSL晶界的比例达到73.25%,形成了大尺寸的“互有Σ3n取向关系”的晶粒团簇,具有最优的晶界特征分布。海水浸泡腐蚀52 d后,B10白铜表面主要形成保护性的Cu_(2)O膜;基体的腐蚀形式随退火温度的升高由剥蚀转变为晶间腐蚀。其中在720℃退火10 min的B10白铜管材具有最高比例的低ΣCSL晶界、最大的晶粒团簇平均尺寸和较少的接近<111>取向的晶粒,同时腐蚀表面易形成较厚且愈致密的Cu_(2)O膜,表现出较佳的耐蚀性能,其浸泡腐蚀速率相比于拉拔态B10白铜管材降低了24.33%。

The large diameter B10 cupronickel pipe blank obtained from the engineering trial is subjected to grain boundary engineering(GBE)treatment:after 21%cold expansion drawing deformation,the finished annealing was carried out and subsequent air cooled.The effects of different annealing temperatures on the grain boundary character distribution(GBCD)and corrosion behavior of as-drawn B10 cupronickel pipes were studied by EBSD,SEM,EDS,XPS and weight loss method.The results show that recrystallization annealing of high temperature helps to optimize the grain boundary character distribution and improve the corrosion resistance of as-drawn B10 cupronickel pipe.The proportion of lowΣCSL grain boundaries reaches 73.25%and large sized grain clusters(GC)with"mutuallyΣ3n orientation relationship"are formed when the cold drawn deformation of B10 cupronickel pipe is 21%and subsequent annealing at 720℃for 10 min,showing that it has the optimal grain boundary character distribution.After being immersed in seawater for 52 days,the surface of B10 cupronickel mainly formed a protective Cu_(2)O film;the corrosion form of the substrate changed from exfoliation corrosion to intergranular corrosion with the increase of annealing temperature.The B10 cupronickel pipe annealed at 720℃for 10 min has the highest proportion of lowΣCSL grain boundaries,the largest average size of grain clusters appear,and fewer grains are close to the<111>orientation.Meanwhile,the corroded surface is prone to form a thicker and denser Cu_(2)O film,thus showing the better corrosion resistance that the immersion corrosion rate is 24.33%lower than that of as-drawn B10 cupronickel pipe.