Carbon nanotubes (CNTs) reinforced Sn-58Bi composites were successfully fabricated through ball-milling method and low temperature melting process.The influence of multi-walled carbon nanotubes (MWCNTs) on the mechanical strength and ductility of Sn-58Bi lead-free alloy was studied.The mechanical test results show that the bending strength of Sn-58Bi-0.03CNTs (mass fraction,%) composite is increased by 10.5% than that of the Sn-58Bi alloy,which can be attributed to the reduction of Sn-rich segregation and the grain refinement.The toughness of Sn-58Bi-0.03CNTs composite is increased by 48.9% than that of the matrix materials.It is indicated that the influence of CNTs on the strength of Sn-58Bi-xCNTs composite is insignificant.In addition,the fracture mechanism of CNTs reinforced Sn Bi composite was analyzed.The corresponding fracture surface comparison between the Sn-58Bi-0.03CNTs composite and the monolithic Sn-58Bi alloy was made to identify the influence of CNTs on the fracture behavior and the reinforcing effect of CNTs.
Al2O3and Tie6Ale4V alloy were brazed with AgeCueTi+B fillers in different brazing conditions.Effects of brazing temperature,holding time and additive Ti content on joints microstructure and shear strength were investigated by scanning electron microscopy,energy dispersive spectrometry,X-ray diffraction,transmission electron microscopy and shear testing.Results indicate that TiCu and Ti(Cu,Al) decrease,but Ti2Cu and Ti2(Cu,Al) increase in brazing seam with increasing brazing temperature,holding time and additive Ti content.Area consisting of Ti3(Cu,Al)3O and TiO near Al2O3becomes gradually discontinuous from continuity when brazing temperature rises or holding time extends.As Ti additive content increases,TiO is absent near Al2O3;area consisting of only Ti3(Cu,Al)3O thickens.TiB whiskers are in situ synthesized by Ti and B atoms during brazing process.The brazing temperature,holding time and additive Ti content on joints microstructure influence the joints shear strength directly.The shear strength of joints,obtained at 850℃ holding for10 min,reaches the maximum of 78 MPa.According to the experimental results,phase diagram and thermodynamics calculation,the interface evolution mechanism of the Al2O3/Tie6Ale4V alloy joint was analyzed.
