Aluminium and aluminium alloy hard soldering technology

Aluminium joints find wide application in the welded structures of air conditioning systems, aeronautics, electrical engineering, radio engineering, and many other areas of industry. In spite of their unquestionable qualities, aluminium and aluminium alloy soldering brings about considerable setbacks, especially in the case of highly alloyed aluminium compounds. The problems result from the physical and chemical properties of such materials. For instance, highly alloyed aluminium requires specific solders of sufficiently low melting point, as well as special sources of heat in order to ensure even soldering. An additional problem results from the considerable aluminium-to-oxygen chemical affinity that produces the resultant Al₂O₃ layer on the surface as an integral and barely fusible coat. This article presents the problems related to aluminium and aluminium alloy joining as well as basic methods of aluminium soldering.     

Selection of soldering temperature for ultrasonic-assisted soldering of 5056 aluminum alloy using Zn-Al system solders

The conditions for sound butt-joints of 5056 aluminum alloy containing 4.6 mass% Mg using Zn-xAl (x = 5, 13, and 38 mass%) solder at the relevant temperatures were investigated. Each solder foil was inserted between faying surfaces of 5056 aluminum rods. Ultrasonic vibration at a frequency of 19 kHz was applied to the faying surfaces through an aluminum substrate at soldering temperatures for 4 s in air. The strength of obtained solder joints was measured by tensile tests. The microstructure in the solder layer after the soldering process was evaluated with an SEM-EDX. The results of tensile tests revealed that joints soldered under the liquidus temperature of Zn-Al solders showed higher strength than joints soldered over the liquidus temperature. In the joints soldered over the solder liquidus temperature, the joint strength decreased with an increase in soldering temperature. It was caused by the formation of MgZn₂ in the solder layer due to dissolution of 5056-Al into the solder liquid during the soldering process. On the other hand, ultrasonic-assisted soldering under the solder liquidus temperature suppressed dissolution of 5056-Al and improved the joint strength by reducing the formation of MgZn₂.     

Dissolution of Cu into Sn-based solders during reflow soldering

Cu contents in pure Sn and Sn-37Pb solders were measured as a function of reflowing time. The results indicated that the contents are significantly higher than that of the Cu solubility limit in each solder. Several plausible causes for the excess dissolution of Cu into the solders were explored with experimental observations.     

Corrosion inhibitors for aluminium and its alloys in neutral media

On the basis of results so far available on inhibitors for water, sodium chloride and other salt solutions new results are reported which were obtained with respect to the inhibition in sodium persulfate solutions. The inhibitors studied in this context show increasing efficiency in the order nicotinic acid - quinonline - pyridine - alpha-picoline - 2,4-lutidine. The efficiency is primarily due to the nitrogen atom facilitating chemisorption of the particular compound to the metal surface. The efficiency may be interpreted in terms of the increased electron density of the heterocyclic system at the nitrogen atom.     

Resistance welding of aluminium and aluminium alloys

Special features of the process of resistance welding of aluminium and its alloys and also equipment manufactured by the CEA and supplied by Weber Comechanics are described.     

亚共晶Sn-Zn系合金无铅焊料的性能

通过差热分析(DTA),研究Sn-xZn合金(x=2.5~9)的非平衡熔化性能,发现在加热速度为5℃/min时,Sn-6.5Zn与Sn-9Zn的熔化特性相同;通过浸润法和铺展法表征Sn-xZn合金在Cu基材表面上的润湿性。结果表明:Sn-6.5Zn在Cu基材表面上的润湿性优于Sn-9Zn。研究速率为10-3s-1和10-1s-1时Sn-xZn的拉伸性能,结果发现:Sn-6.5Zn的抗拉强度与Sn-9Zn的相当,而延伸率高于Sn-9Zn。以搭接焊及界面剪切实验研究Sn-xZn/Cu焊点界面强度,发现焊点界面剪切强度随x的增加而提高,在x≥6.5时趋于稳定;x=6.5时剪切力最大,表明Sn-6.5Zn在Sn-Zn系中具有最好的钎焊工艺性能。     

Relative porosity in aluminium and in aluminium alloys

Abstract

Pores are readily formed in aluminium alloy castings. Density and porosity area fraction are often used quantitatively to evaluate the quality of aluminium alloy castings. This study used the relative porosity, the ratio (d _c ? d _r)/d _c, where d _c is the density of the chilled sample and d _r is the density of the reduced-pressure test sample, to evaluate the quality of aluminium and Al–6Si and Al–13Si alloys. The bursting of degassing bubbles on the free surface of the melt brought debris of oxide particles into the melt, which were eventually trapped in the castings after pouring. These particles were accompanied with air pockets and/or engulfed by bubbles, resulting in pores shown on the sections of poured castings.     

Mechanical properties of QFP micro-joints soldered with lead-free solders using diode laser soldering technology

Soldering experiments of quad flat package(QFP) devices were carried out by means of diode laser soldering system with Sn-Ag-Cu and Sn-Cu-Ni lead-free solders, and competitive experiments were also carried out not only with Sn-Pb eutectic solders but also with infrared reflow soldering method. The results indicate that under the conditions of laser continuous scanning mode as well as the fixed laser soldering time, an optimal power exists, while the optimal mechanical properties of QFP micro-joints are gained. Mechanical properties of QFP micro-joints soldered with laser soldering system are better than those of QFP micro-joints soldered with IR reflow soldering method. Fracture morphologies of QFP micro-joints soldered with laser soldering system exhibit the characteristic of tough fracture, and homogeneous and fine dimples appear under the optimal laser output power.     

Process window for manufacturing of semi-solid aluminium alloys

Abstract

The demands of the automotive industry for lightweight technologies stimulate research on new materials and the development of corresponding innovative production methods. The thixocasting process is based on standard high pressure die casting with the exception that mould filling takes place in the semi-solid state. In comparison to other processes, thixocast parts generally have better mechanical properties. For an industrial application and for the safe handling of the partially solidified alloys in series manufacturing, an exact knowledge of the material behaviour is necessary. This paper attempts to give an overview of the relevant parameters influencing the successful processing of semisolid metals with thixotropic properties. With this aim, several parameters considered to be of major importance for the process were selected and analysed and correlated with the desired end properties. The influence of temperature to obtain an optimally heated semi-solid billet with thixotropic properties was the first parameter to be evaluated. Subsequently, the effect of wall thickness (25–0.5 mm) and metal velocity during mould filling on the mechanical properties, grain texture development and segregation phenomena was studied and analysed. As a result of the investigations, a preliminary process window for the successful processing of semi-solid aluminium alloys was defined.     

Recent developments in arc welding with shielding gas of aluminium and its alloys

Summary

Aluminium and its alloys are frequently used in many sectors of industry. Arc welding should adapt to these metals, particularly with regard to productivity and quality. Optimisation of recent innovations are presented here.

In order to adapt to the technological developments of the various sectors of the transport industry (automotive, rail, shipbuilding, aircraft and aerospace), the electricity industry, and the chemical and food‐processing industries, welding processes must also adapt to light metals (aluminium and its alloys) in terms of the productivity and quality required by these industrial sectors.

Recent developments (refinements and innovations) in welding processes, notably MIG welding (dual‐wire welding, modulated spray MIG welding) due to a global approach (procedure, consumables, gas) enable useful alternative solutions to be found for the usual applications of the process.     

Droplet transition for plasma-MIG welding on aluminium alloys

The synchronous acquisition system of droplet image inspection and arc electric signals were established and the droplet transition characteristics of aluminum alloys were researched in the plasma-MIG welding process.Typical droplet transition modes include globular transfer mode,short circuiting transfer mode,metastable spray transfer mode and projected transfer mode.The result indicates that MIG droplet transfer frequency and droplet transfer modes are changed by introducing the plasma arc in the plasma-MIG welding process compared with the MIG welding on the aluminum alloys,which broadens the range of welding parameters when the stable welding process proceeds.The metastable spray transfer and projected transfer mode are proved to be the most optimal modes by comparing the stability of electronic signal,droplet transition,weld appearance and weld penetration.