Effect of process parameters on microstructure and mechanical properties of a nickel-aluminum-bronze alloy fabricated by laser powder bed fusion

This work investigated the effect of process parameters on densification,microstructure,and mechanical properties of a nickel-aluminum-bronze(NAB)alloy fabricated by laser powder bed fusion(LPBF)additive manufacturing.The LPBF-printed NAB alloy samples with relative densities of over 98.5%were obtained under the volumetric energy density range of 200−250 J/mm^(3).The microstructure of the NAB alloy printed in both horizontal and vertical planes primarily consisted ofβ'martensitic phase and bandedαphase.In particular,a coarser-columnar grain structure and stronger crystallographic texture were achieved in the vertical plane,where the maximum texture intensity was 30.56 times greater than that of random textures at the(100)plane.Increasing the volumetric energy density resulted in a decrease in the columnar grain size,while increasing the amount ofαphase.Notably,β_(1)'martensitic structures with nanotwins and nanoscaleκ-phase precipitates were identified in the microstructure of LPBF-printed NAB samples with a volumetric energy density of 250 J/mm^(3).Furthermore,under optimal process parameters with a laser power of 350 W and scanning speed of 800 mm/s,significant improvements were observed in the microhardness(HV 386)and ultimate tensile strength(671 MPa),which was attributed to an increase in refined acicular martensite.

SKIKDA炼厂穿路地管腐蚀防护问题分析及对策

为确保穿路段埋地管线腐蚀防护效果,结合阿尔及利亚SKIKDA炼厂区域穿路管线的腐蚀情况,总结并分析了穿路段地管发生腐蚀的主要原因及应对措施。研究结果表明:敷设方式、涂层类型、绝缘效果、套管结构、阴极保护设计等因素都会对穿路段地管的防腐蚀造成显著影响。为保证穿路地管的防腐蚀效果,应尽量避免穿越段管线走向突变造成腐蚀性介质沉积。在应力核算通过的情况下尽量避免使用套管,以避免套管内腐蚀介质积聚并对阴极保护电流产生屏蔽;保证穿路段地管与地上管线或管托与管墩之间的绝缘,以避免阴极保护电流流失。在无法对地上管线和管墩进行有效绝缘隔离的情况下应采用多种途径补加阴极保护,并同时兼顾钢筋混凝土阴极保护要求。

轻钢轻混凝土墙体免拆模板施工技术

介绍了轻钢轻混凝土墙体免拆模板的技术特点、免拆模板材料指标、墙体免拆模板的构造要求等,并与传统木模板、钢板网抹灰工艺进行了经济性对比分析。以试验房为例,介绍了墙体免拆模板安装及支护的施工过程,并在试验测试研究的基础上,结合样板房建造,验证了轻钢轻混凝土墙体免拆模板构造及施工工艺。