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The purpose of this paper is to determine the failure reasons and failure mechanism of the commercially pure titanium air conditioning condenser.

In this paper, chemical analysis, metallographic observation, visual examination and scanning electron microscope examination, corrosion products analysis and working conditions analysis were adopted for determining the reasons for the failure of the condenser.

The results indicated that TA2 titanium pipe perforation failure is caused by the synergistic effect of crevice corrosion and deposit corrosion. The corrosion processes can be divided into three steps.

This research is an originality study on the failure case of a commercially pure titanium air conditioning condenser. This study makes up for the shortage of titanium alloy failure cases and also gives the result of the failure reason and failure mechanism for titanium, which has an engineering significance.

Materials with a high thermal conductivity, such as Cu-alloys hold the most interest to the plastic moulding industry. Additive manufacturing (AM), especially selective laser melting (SLM) of metals, allows the production of parts with complicated internal cooling and increased production efficiency. The portfolio of alloys for metal AM is limited and still missing process parameters for the processing of copper alloys. This paper aims to preview the process parameters of high-strength alloy Cu7.2Ni1.8Si1Cr processed by SLM.

An experimental approach is adopted to investigate porosity and mechanical properties of SLM specimens and its comparison with standard material AMPCOLOY 944. Optimization of porosity was performed using line and cube specimens; mechanical properties and microstructure were evaluated by tensile testing and metallography.

Optimum processing parameters for fabrication of Cu-alloy specimens with a relative density of 99.95 per cent were identified, and no cracks were detected. Mechanical testing of SLM specimens showed the ultimate tensile strength, proof stress of 0.2 and elongation of 380, 545 MPa and 16.9 per cent. The alloy is suitable for laser AM, thanks to its processability at a relatively high laser scanning speeds and thus its promising price of part/costs ratio.

The paper describes the initial state of research – the follow-up tests focussed on mechanical testing, fatigue and statistical evaluation need to be conducted. The process parameters are developed only for bulk geometry – optimal setup for lattice structures and thin walls has not been explored yet.

The research findings in this work could be used for production of 3D printed parts and after the tuning of additional parameters, e.g. for up- and down-skin zones, could be used for special application such as energy exchange.

This work produces the processing of new material suitable for laser AM. Cu7.2Ni1.8Si1Cr alloy could be the prospective material from the group of Cu alloys suitable for moulds manufacturing and thermal applications.

The objective of this study is to investigate the effect of various parameters on rapid prototyping parts for processes of sintering metallic powder by using Nd:YAG laser via the design of experiments (DOE) method.

Experiments based on the DOE method were utilized to determine an optimal parameter setting for achieving a minimum amount of porosities in specimens during the selective laser sintering (SLS) process. Analysis of variance (ANOVA) was further conducted to identify significant factors.

A regression model predicting percentages of porosities under various conditions was developed when the traditional Taguchi's approach failed to identify a feasible model due to strong interactions of controlled factors. The significant factors to the process were identified by ANOVA.

Four controlled factors including pulse frequencies and pulse durations of laser beams, times of strikes of a pulse applying on a single laser spot and particle sizes of the powder base material had significant influence on the sintering process. Future investigation planned to be carried out for achieving multiple quality targets such as the hardness and the density for 3D parts.

The implementation of the DOE method provided a systematic approach to identify an optimal parameter setting of the SLS process; thus, the efficiency of designing optimal parameters was greatly improved. This approach could be easily extended to 3D cases by just including additional parameters into the design. Additionally, utilization of the normality analysis on the residual data ensured that the selected model was adequate and extracted all applicable information from the experimental data.

The purpose of this study is to verify how the carbon doping of the WC-Co cemented carbide (CC) affected their structure before their processing by hot isostatic pressing (HIP) technology.

The samples for this experiment were fabricated by selective laser melting technology (SLM) using a YAG fiber laser with a power of P = 40 W and a scanning speed of 83 mm/s. The subsequent carbon doping process was performed in a chamber furnace at 900 0 C for 1, 4 and 12 h. The HIP was performed at 1,390°C and pressures of 40 MPa, 80 MPa and 120 MPa. The changes induced in the structures were evaluated using X-ray diffraction and various microscopic methods.

X-ray diffraction analysis showed that the structure of the samples after SLM consisted of WC, W₂C, Co₄W₂C and Co phases. As a result of the increase in the carbon content in the structure of the samples, the transition carbide W₂C and structural phase Co₄W₂C decayed. Their decay was manifested by the coarsening of the minor alpha phase (WC), which occurred both during the carburizing process and during the subsequent processing using HIP. In the samples in which the structure was carburized prior to HIP, only the structural phases WC and Co were observed in most cases.

The results confirm that it is possible to increase the homogeneity of the CC structure and thus its applicability in practice by additional carburization of the sample structure with subsequent processing by HIP technology.

The purpose of this paper is to present the results of an atomic force microscopy (AFM) based approach to local impedance spectroscopy (LIS) measurement performed on AA2024 and AA2024‐T3 aluminium alloys.

AFM‐LIS measurements were performed ex‐situ without the electrolyte environment, so in fact the electrical not electrochemical impedance was obtained.

Relative local impedance values recorded for AA2024 alloy during the researches carried out were maximally approximately three orders of magnitude higher than the ones obtained for age‐hardened AA2024‐T3 alloy. Moreover, in the case of AA2024‐T3 alloy, a region located in the interior of α crystals exhibited localized impedance one order of magnitude higher than that measured at its grain boundary when affected by intergranular corrosion.

The paper presents differences in localized impedance between grain and grain boundaries activity.

The purpose of this paper is to study the effect of the addition of a small amount of Al (0.1 percent) on the properties of lead‐free solder type Sn‐4Ag‐0.5Cu (SAC 405).

The soldering properties of wettability and spreadability on a Cu substrate were studied, and the effect of Al on the growth of intermetallic compounds (IMCs) was observed. The shear strength of soldered joints was assessed. For comparison, soldering and strength tests were carried out on SAC 405 and SAC 405+ Al solders. Soldering was performed with an activated flux type ZnCl₂‐NH₄Cl, with non‐activated flux (rosin), and without flux in the air.

Experimental results show that Al addition slightly reduces the wettability and spreadability of SAC 405 solder. Also, the shear strength is moderately reduced, dropping by 8 MPa on average. Differential scanning calorimetry (DSC) analysis showed that the melting point of SAC 405+0.1%Al solder was increased to 221°C.

The positive effect of a small Al addition is due to the fact that it hinders the growth of IMCs formed on the contact surface with Cu substrate. The width of the transition zone of IMC was reduced by approximately 2 to 3 μm, depending on the soldering temperature.

The reduction in IC package lead pitches in surface mount solder assembly and the current high emphasis on quality and reliability of printed circuit assemblies have created a requirement for microanalysis of fine pitch solder joints in manufacturing situations. Of particular interest are metallographic analysis, detection of solder joint defects and mechanical strength testing of solder joints. Much has been published in the literature on the results of such evaluations in specific applications but little has been available on procedures for use in the microanalysis itself, particularly for fine pitch solder joints. Detailed procedures for fine pitch solder joint microanalysis, which the authors have verified down to 0.5 mm (0.02 in.) lead pitches, are presented. In particular, the authors present procedures for metallographic examination of tin‐lead and tin‐lead‐silver solder joints. In addition, test parameters are given for a repeatable technique of fine pitch solder joint mechanical strength testing that allows mechanical strength measurements to be obtained from almost every lead on a fine pitch surface mount IC package.

In thermal and nuclear power plants, numerous corrosion phenomena observed in copper alloy condenser tube nests have been identified by means of metallography. Particular importance has been given in the paper to verification of secondary dezincification, initiated at the boundaries of the α‐grains in copper tubes. Typical phenomena of corrosion under stress and of erosion‐corrosion have been observed in other copper alloy tube nests, with circulation of sea and river water. In some instances a semi‐quantitative check of the phenomenon on the whole tube nest, by means of eddy currents, has been made possible through the simultaneous application of metallographic analysis.

The purpose of this paper is to quantify the corrosion damage evolution that has occurred on the aircraft aluminum alloy 2024 after the exposure to Exfoliation Corrosion Test (EXCO) solution. Moreover, the effect of the evolving corrosion damage on the materials mechanical properties has been assessed. The relevance of the corrosion damage induced by the exposure to the laboratory EXCO for linking it to the damage developed after the exposure of the material on several outdoor corrosive environments or in service is discussed.

To induce corrosion damage the EXCO has been used. For the quantification of corrosion damage the metallographic features considered have been pit depth, diameter, pitting density and pit shape. The effect of the evolving corrosion damage on the materials mechanical properties has been assessed by means of tensile tests on pre corroded specimens.

The results have shown that corrosion damage starts from pitting and evolves to exfoliation, after the development of intergranular corrosion. This evolution is expressed by the increase of the depth of attack, as well as through the significant growth of the diameter of the damaged areas. The results of the tensile tests performed on pre corroded material made an appreciable decrease of the materials tensile properties evident. The decrease of the tensile ductility may become dramatic and increases on severity with increasing corrosion exposure time. SEM fractography revealed a quasi-cleavage zone beneath the depth of corrosion attack.

The results underline the impact of corrosion damage on the mechanical behavior of the aluminum alloy 2024 T3 and demonstrate the need for further investigation of the corrosion effect on the structural integrity of the material. This work provides an experimental database concerning the quantification of corrosion damage evolution and the loss of material properties due to corrosion.

The purpose of this paper is to study the drop reliability of ball-grid array (BGA) solder joints affected by thermal cycling.

The drop test was made with the two kinds of chip samples with the thermal cycling or not. Then, the dyeing process was taken by these samples. Finally, through observing the metallographic analysis results, the conclusions could be found.

It is observed that the solder joint cracks which were only subjected to drop loads without thermal cycling appeared near the BGA package pads. The solder joint cracks which were subjected to drop loads with thermal cycling appear near the printed circuit board pads.

This paper obtains the solder joint cracks picture with drop test under the thermal cycling.