Improving the Fatigue Strength of Laser Powder Bed-Fused AISI M3:2 by Hot Isostatic Pressing

Laser additive manufacturing enables the one-step fabrication of complex parts. However, pores and carbide networks, which are not avoidable from the laser powder-bed fusion (LPBF) process, deteriorate the fatigue strength significantly. Hot isostatic pressing (HIP) with integrated heat treatment is a powerful post-treatment that densifies the material and modifies the microstructure. Herein, AISI M3:2 samples are produced by LPBF and then are either austenitized, quenched, and tempered in a HIP unit under pressure or are only hardened and tempered in a vacuum oven. The corresponding microstructure is analyzed by optical microscopy, scanning electron microscopy using energy-dispersive X-ray spectroscopy, and X-ray diffraction. The fatigue strength is determined by rotation bending tests. Fracture surfaces are observed under scanning electron microscopy for failure analysis. While both post-treatments lead to similar microstructure, the fatigue strength is significantly improved by the HIP process.     

边界扫描在数模混合电路板级测试中的设计与应用

针对飞控系统某数模混合电路板测试需求,在不利用外部信号源、信号采集设备的条件下,利用边界扫描技术进行测试系统设计。介绍了PCI-410边界扫描核心套件和ScanWorks测试软件,对边界扫描测试方法进行研究,详细说明了测试系统方案设计、测试流程开发步骤以及测试程序执行方式,并通过实际测试,验证了设计的可行性,为数字电路板和简单的数模混合电路板的测试提供了实用的测试方法和手段,具有很好的应用价值。     

选铁尾矿中极低品位磷矿物浮选回收试验北大核心

某选铁尾矿由于矿石中磷、钛伴生有价元素含量很低,直接对其进行磨选,选矿成本高,影响其回收磷、钛的经济性;此外,矿石中存在较多的含钙脉石矿物和易浮易泥化脉石矿物,对极低品位磷矿物的浮选回收干扰很大,并影响磷精矿品位的提高。根据矿石性质,采用原矿原浆浮选—磷粗精矿再磨再选抛尾工艺进行了磷浮选回收试验研究,即首先在不磨矿条件下采用高效磷矿物组合活化剂(碳酸钠+BK116A)和磷选择性捕收剂BK410B浮选回收磷;然后磷粗精矿再磨再选后抛尾,实现了矿石中极低品位磷矿物的有效回收。闭路试验获得含P_(2)O_(5)30.10%、P_(2)O_(5)回收率87.61%的磷精矿。