航空增材SLM制件对比试块的代表性研究

选区激光熔化(SLM)制件结构形状复杂,常规射线检测技术对于结构复杂的零件,极易出现检测盲区。工业计算机层析成像检测(CT)技术可实现零件的整体检测,对于复杂零件无检测盲区,而目前航空增材SLM工业CT对比试块设计缺少相关试验验证依据,因此,针对对比试块代表性问题,研究了缺陷盲孔或通孔、相同尺寸不同位置缺陷、柱面粗糙度、基体成型方式对工业CT检测结果的影响规律。研究结果表明,通孔相较于盲孔更容易检出,相同尺寸情况下缺陷所处位置对孔洞类缺陷的检出无明显影响,但缺陷越靠近中心处,检测结果受环形伪影影响越大,柱面粗糙度、基体成型方式对孔洞类缺陷的检出均无明显影响。

Aging-induced two-stage reverse martensitic transformation behavior in Co_(46)Ni_(27)Ga_(27) high-temperature shape memory alloy

The effect of austenite aging at 823 K on the microstructures and martensitic transformation behavior of Co 46 Ni 27 Ga 27 alloy has been investigated using optical microscopy （OM）, transmission electron microscopy （TEM）, X-ray diffraction analysis （XRD）, and differential scanning calorimeter （DSC）. The microstructure observation results show that the unaged Co 46 Ni 27 Ga 27 alloy is composed of the tetragonal nonmodulated martensite phase and face-centered cubic γ phase. It is found that a new nanosized fcc phase precipitates in the process of austenite aging, leading to the formation of metastable age-affected martensite around the precipitates with composition inhomogeneity. Two-stage reverse martensitic transformation occurs in the samples aged for 2 and 24 h due to the composition difference between the age-affected martensite and the original martensite. For the Co 46 Ni 27 Ga 27 alloy aged for 120 h, no reverse transformation can be detected due to the disappearance of the metastable age-affected martensite and the small latent heat of the original martensite. The martensitic transformation temperatures of the Co 46 Ni 27 Ga 27 alloy decrease with an increase in aging time.

多焦点超快激光并行加工单晶金刚石

金刚石表面的周期性微纳结构具有增透减反、提高量子运输效率等功能,在航空航天、生物医学、集成光子学器件等领域被广泛应用。传统的电子束曝光、离子刻蚀等加工方法涉及较多步骤,对环境要求高,加工效率远远无法满足使用需求。为了解决这些问题,超快激光微加工技术被引入,其因具有低热效应、高精度和高度可控的可设计性而备受关注。然而,单光束激光无法实现快速高效加工。为了提高加工效率,本课题组利用空间光调制器对飞秒激光光束进行5×5阵列分光,对金刚石进行了多焦点并行加工,实现了圆柱、球形、金字塔、圆锥等三维阵列结构的高精度、高效率加工。拉曼光谱结果显示,激光加工区域未发现明显的石墨化G带和激光热影响区,这说明多焦点超快激光并行加工后金刚石不会产生明显的物性改变。超快激光多焦点并行加工单晶金刚石对于开发高速、高精度的金刚石加工新技术具有重要意义。