Role of inclination angle on columnar-to-equiaxed transition in the eutectic Al-5Mg-2Si alloy fabricated by laser powder bed fusion

In this study,the effect of inclination angles relative to the building direction in the additively manufactured eutectic Al-5Mg-2Si alloy was investigated through the laser powder bed fusion(LPBF).The microstructures and mechanical properties of the Al-5Mg-2Si alloy manufactured with different inclination angles(0°,30°,45°,60°and 90°)were reported and discussed.It is found that the“semicircular”melt pool(MP)in the load bearing face of 0°sample was eventually transformed into“stripe-like”MP in the 90°sample,accompanied by an increased fraction of melt pool boundaries(MPBs).Moreover,the microstructural analysis revealed that the columnar-to-equiaxed transition(CET)of theα-Al grains and eutectic Mg2Si was completed in the 90°sample,which were significantly refined with the average size of 10.6μm and 0.44μm,respectively.It is also found that the 90°sample exhibited good combination of strength and elongation(i.e.yield strength of 393 MPa,ultimate tensile strength of 483 MPa and elongation of 8.1%).The anisotropic mechanical properties were highly associated with the refined microstructures,thermal stress,and density of MPBs.Additionally,the CET driven by inclination angles was attributed to the variation of thermal conditions inside the local MPs.

一种无线通信网络信息敏感密文数据差错恢复方法

无线通信网络信息在复杂网络环境下加密,容易出现丢失差错,对丢失数据恢复过程忽略了数据所处的序列位置,可恢复的信息过少,导致效果不佳。为提高无线通信网络敏感密文数据差错恢复的精度和效率,提出基于一种无线通信网络信息敏感密文数据差错恢复方法。采集无线通信网络数据,运用马尔科夫聚类识别敏感信息属性;将算术码、时间标签与签名组成ANBD码,创建差错信息定位模型;基于长短期记忆网络挖掘数据时序特征,以差值最小为核心构建差错恢复约束条件,完成敏感密文数据差错恢复。实验结果表明:应用所提方法进行差错恢复提高了数据恢复精度和效率。

不同角度晶界对单层多晶二硫化钼摩擦性能的影响

目的考察不同角度晶界对单层多晶二硫化钼纳米片摩擦性能的影响,并探究其摩擦耗散机理。方法用化学气相沉积法(CVD)制备单层多晶二硫化钼(MoS2),通过原子力显微镜力曲线测试和摩擦力实验,分别得出无晶界区域和晶界处的粘附力、摩擦系数、摩擦耗散。结果对于单层多晶MoS2,无晶界区域粘附力为7.20 nN,不同角度晶界处粘附力为11.11nN至11.40 nN。无晶界区域及−6°、33°、88°晶界区域(400 nm×400 nm)摩擦系数分别为0.00619、0.00645、0.00737和0.01760。在30~150 nN法向载荷范围内,探针经过无晶界区域产生的摩擦耗散变化范围为33.93×10^−16~46.88×10^−16 J,−6°晶界区域为37.15×10^−16~52.09×10^−16 J,33°晶界区域为38.76×10^−16~55.18×10^−16 J,88°晶界区域为46.59×10^−16~59.72×10^−16 J。结论晶界处吸附的极性粒子加强了探针与MoS2表面的相互作用,使得晶界处的粘附力比无晶界区域的大,但晶界角度对粘附力的影响不大。在一定测试范围内,晶界区域的摩擦系数要比无晶界区域的摩擦系数大,并随晶界角度增加而增大,摩擦过程中晶界区域产生的摩擦耗散也比无晶界区域多。晶界角度的不同可能会造成晶界处的弯曲刚度存在差异,从而探针滑移经过不同角度晶界时导致不同程度的褶皱效应。并且随着法向载荷的增大,探针在MoS2表面引起的面内变形程度越来越高,这样会引起表面褶皱效应,从而导致摩擦过程中产生的能量耗散随晶界角度和法向载荷增大而增加。

水利工程中不同种组合多桩型复合地基的应用

复合型地基是指采用两种或者两种以上处理地基的方法进行地基处理,根据不同处理地基的方法,选择合适的组合,可以达到比单一处理地基方法缩短时间、节省投资、提高地基承载力、减少变形等方面的优点。目前,已有众多工程进行了复合地基处理,取得了良好的效果。因此,通过对不同组合的多桩型复合型地基进行探讨,以供实际工程中选择应用。