[en] The compressive creep property of Mg–4Al–RE (AE41) alloys is investigated using a homemade compressive creep device. The microstructure of as-cast and post-crept AE41 alloys is observed by scanning electron microscope (SEM), and the precipitation phases in the alloys are analyzed by X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). The results show that the compressive creep rates of AE41 alloys are decreased with increasing duration in the primary creep stage, and the steady state compressive creep rates are decreased with increasing calcium and strontium concentrations. The steady state compressive creep rate of AECJ411202 alloy is 1.36721×10"−"7 mm/s that is 8.34 times lower than that of AE41 alloy. The poor compressive creep resistance of AE41 alloys is caused by the softening of β-Mg_1_7Al_1_2 phase. The compressive creep resistance of Mg–Al–RE–Ca and Mg–Al–RE–Ca–Sr alloys is improved by the grain refinement, and the granular Al_2Nd, bone (Mg, Al)_2Ca and fish-bone Al_4Sr hindering the dislocation climbing and grain boundary sliding

[en] The wettability, microstructure and mechanical properties of multi-walled carbon nanotube (CNT)-reinforced Sn-58Bi composite solder joints were investigated. The results indicate that the wettability of the Sn-58Bi solder is improved and the growth of interfacial intermetallic (IMC) compounds for solder joints is restrained by CNTs. The thickness of the IMC layers is decreased with increasing CNTs concentration. The microstructure of the Sn-58Bi composite solders is refined, the maximum tensile strength and shear strength are obtained by adding the optimum CNTs content about 0.01 wt.%. However, excessive content of CNTs addition can deteriorate the properties. The creep rupture life of Sn-58Bi solder joint and Sn-58Bi-0.01CNTs solder joint is decreased with increasing load, temperature and current density. The average creep rupture life of Sn-58Bi-0.01CNTs composite solder joint is 60% higher than that of the plain solder joint.

[en] The effect of aging temperature on microstructure and mechanical properties of Sn–9Zn–xZrC (x = 0, 0.06) solder joints was investigated. The results showed that the wettability of Sn–9Zn based alloys was improved by ZrC nanoparticles, the spreading areas of Sn–9Zn–xZrC (x = 0–0.12) were increased firstly then decreased with increasing ZrC content. The spreading area of Sn–9Zn was about 143.64 mm² and reached maximum about 190.92 mm² of Sn–9Zn–0.06ZrC. The microstructure of Sn–9Zn–0.06ZrC solder alloy consisted of β-Sn, Sn–Zn eutectic and intermetallic compounds (IMCs), and the microstructure of Sn–9Zn alloy was refined by adding appropriate amounts of ZrC nanoparticles. The interfacial IMCs at the β-Sn boundary in the Sn–9Zn–0.06ZrC solder joint was Cu₅Zn₈, and partial Cu₅Zn₈ was transformed to Cu₆Sn₅ during aging treatment. The IMCs layer thickness was dominated by aging temperature, and ZrC facilitated the IMCs layer growth. The tensile strength of Sn–9Zn based solder joints was enhanced by adding ZrC particles, and then are decreased simultaneously with increasing aging temperature. The fracture surface of Sn–9Zn joints after aging was mainly composed of uniform dimples, and the fracture mechanism of Sn–9Zn based solder joints was ductile fracture.

[en] In this study, the friction stir processing (FSP) was employed to modify 1060 Aluminum (Al) surface composites reinforced with lead (pb) particles of different mass fractions (0–30 wt%). The effect of the Pb content on the microstructure, mechanical properties and wear resistance of Al-Pb alloy layer was investigated. The results indicated that an excellent metallurgical bonding was formed between Pb-rich phase and Al matrix by FSP, and most lead particles were uniformly distributed in the low regions of Al-Pb alloy layer. The tensile strength of FSPed composites was inferior to that of pure Al, while the elongation of FSPed composites with Pb content of 0-18 wt% was obviously enhanced. The wear resistance of FSPed composite was increased firstly and then decreased with increasing Pb content. Amongst the FSPed Al-Pb composite, specimen with 18 wt% of Pb showed the optimal wear resistance with low coefficient of friction. (paper)

[en] The laser deposited IN718 alloys were fabricated with laser cladding system under different conditions to estimate the sensitivity of weld metal liquation cracking. The microstructure and the crack characterization of the laser deposited IN718 alloy were investigated, and the effect of metallurgical factors and residual stress on the crack sensitivity was analyzed. The results showed that the continuous dendritic Laves was precipitated and formed a Lave–austenite interface with ambiguous nanohardness distribution. The weld metal liquation cracking was propagated along the laser scanning direction and the buildup direction in the laser deposited IN718 alloy simultaneously, and the Nb-/Mo-riched fine granular clusters were formed in the crack surface. The precipitation amount of the coarse eutectic phases, presented as dendrite or network, was increased in the laser deposited alloy fabricated with IN718/C-Fe-Cr composite powder and slow cooling rate. The total crack length and the maximum crack length were decreased by increasing cooling rate, and the transverse residual stress was increased with increasing buildup layer number. The crack sensitivity of the laser deposited IN718 alloy was increased by the crack initiation provided by the metallurgical defects and the eutectic phases with low melting temperatures, and then, crack propagated along the continuous phase under the transverse residual stress.

[en] The microstructural evolution and IMCs growth behavior of Sn-58Bi and Sn-58Bi-0.25Mo solder joints were investigated. The results showed that the microstructure is coarsened, the IMCs layer thickness is increased and the tensile strength of Sn-58Bi and Sn-58Bi-0.25Mo solder joints is decreased with increasing aging time and temperature. Aging temperature is the key factor that causes the excessive IMCs growth of the solder joint compared with aging time, and the activation energy of IMCs layer growth of Sn-58Bi and Sn-58Bi-0.25Mo solder joints is 48.94 kJ mol⁻¹ and 53.79 kJ mol⁻¹, respectively. During the aging treatment, the microstructure of Sn-58Bi solder joint is refined by adding Mo nanoparticles, and the appropriate IMCs layer thickness and improved mechanical properties are obtained by Sn-58Bi-0.25Mo solder joint. (paper)

[en] The effect of WC nanoparticles on the spreadability, microstructure and mechanical properties of Cu/Sn57.6Bi0.4Ag/Cu solder joints was investigated. The results showed that the spreadability of Sn57.6Bi0.4Ag composite solder was enhanced by WC nanoparticles, and the spreadability was increased first and decreased with increasing WC content next; when the content of WC was 0.1 wt%, the solder got relatively optimal spreadability. The dispersed WC particles provided the heterogeneous nucleation sites during the soldering process and led to the microstructure refinement of Sn57.6Bi0.4Ag solder alloy. WC particles restrained the growth rate of IMC by reducing the surface energy of Cu₆Sn₅, the shear strength of Sn57.6Bi0.4Ag-xWC/Cu (x = 0, 0.1) solder joints decreased seriously with increasing aging time, WC particles improved the shear strength and toughness of Sn57.6Bi0.4Ag/Cu solder joints by refining the microstructure. (orig.)

[en] The microstructure and the mechanical properties of the Sn-58Bi based composite solder joints reinforced by different content vanadium (V) particles were investigated. The results showed that the Sn-58Bi-0.4 V solder alloy with spreading area 52.51 mm² exhibited an appropriate wettability. The microstructure of Sn-58Bi solder alloy consisted of rich Bi phase and rich Sn phase, and the spacing of Sn-rich phase was reduced from 2.13 μm to 0.98 μm by adding 0.4 wt% V particles. The intermetallic compounds (IMCs) layer of Cu/Sn-58Bi/Cu solder joint was presented as scallop shape, and the IMCs layers thickness of Cu/Sn-58Bi-xV/Cu (x = 0–1.0) solder joints was firstly increased to the maximum 0.95 μm and then decreased with increasing V content. The tensile strength and the shear strength of Cu/Sn-58Bi/Cu solder joint were 72.76 MPa and 38.44 MPa, then were reached the maximum 83.81 MPa and 42.81 MPa by Cu/Sn-58Bi-0.4 V/Cu solder joint, respectively. The tensile and the shear fracture morphologies of Cu/Sn-58Bi-xV/Cu (x = 0–1.0) solder joints with the brittle fracture mode were both presented as cleavage fracture, and a couple of dimples occur in the tensile and the shear fracture of Cu/Sn-58Bi-0.4 V/Cu solder joint. (paper)

[en] The effect of trace ZrC on the wettability, microstructure and mechanical properties of Sn-9Zn composite solder alloy joints was investigated. The results indicated that the wettability of the Sn-9Zn based composite solder alloy was improved and the microstructure was refined by adding appropriate amount nanoparticle ZrC. The microstructure of Sn-9Zn based composite solder alloys consists of primary Sn and Sn-Zn eutectic, and the excellent wettability and refined microstructure can be obtained by adding about 0.06 wt% ZrC. The interfacial intermetallic compounds (IMC) layer in the Sn-9Zn based composite solder alloy joints consists of Cu₅Zn₈ and Cu₆Sn₅. IMC layer thickness of Sn-9Zn based composited solder alloys joints is increased with increasing ZrC content. The tensile strength and the shear strength of Sn-9Zn based composite solder alloys joints relate to the ZrC content, and the maximum mechanical properties of solder joints are obtained by adding about 0.06 wt% ZrC, and the fracture mechanism of the Cu/Sn-9Zn-(0-0.09) ZrC/Cu solder joints is ductile fracture. (paper)

[en] This study aims to investigate Nd:YAG laser welding of dissimilar Mg/Al joints using Cu interlayer. Welding processing, microstructure and the corrosion properties of laser-welded Mg/Al joints with Cu interlayer were discussed. According to the results, the pulse width is the most important influence on weld formation of dissimilar Mg/Al joints, followed by laser power and welding speed. Selected optimization process parameters of 1 mm AZ31B/6061 lap welding are: laser power is 6 KW, laser pulse width is 7.5 ms, velocity is 1.2 mm s⁻¹. There is no obvious pore and cracks in the Mg/Al joint with Cu interlayer. The Mg-Al-Cu compounds are introduced to the Mg-Al binary system and then the microstructure of the fusion zone is optimized and improved. The IMCs are mainly consisted of Mg₁₇Al₁₂, Al₃Mg₂ and Al₆CuMg₄. The plastic of (Al₆Cu)Mg₄ is better than that of Mg₁₇Al₁₂, Al₃Mg₂ according to the calculation. Model of mechanism of interfacial reaction layer is established. Because of the existence of Cu, the reaction of Mg, Al was depressed and the generation of MgAl compounds was decreased. The corrosion resistance of alloys in different conditions decreased in the following order: 6061 Al> the weld beam >AZ31B Mg. (paper)