Influence of the Production Process on the Binding Mechanism of Clinched Aluminum Steel Mixed Compounds

The multi-material design and the adaptability of a modern process chain require joining connections with specifically adjustable mechanical, thermal, chemical, or electrical properties. Previous considerations primarily focused on the mechanical properties. The multitude of possible combinations of requirements, materials, and component- and joining-geometry makes an empirical determination of these joining properties for the clinching process impossible. Based on the established and empirical procedure, there is currently no model that takes into account all questions of joinability—i.e., the materials (suitability for joining), design (security of joining), and production (joining possibility)—that allows a calculation of the properties that can be achieved. It is therefore necessary to describe the physical properties of the joint as a function of the three binding mechanisms—form closure, force closure, and material closure—in relation to the application. This approach illustrates the relationships along the causal chain “joint requirement-binding mechanism-joining parameters” and improves the adaptability of the mechanical joining technology. Geometrical properties of clinch connections of the combination of aluminum and steel are compared in a metallographic cross-section. The mechanical stress state of the rotationally symmetrical clinch points is qualified with a torsion test and by measuring the electrical resistance in the base material, in the clinch joint, and during the production cycle (after clinching, before precipitation hardening and after precipitation hardening).

The Effect of Laser Beam Welding Parameters onto the Evolving Joints Geometry

In our research the effect of a new type of laser beam parameters during the laser welding have been investigated with 80 different welding parameters. The laser welding parameters such as the laser power, laser beam spot size on the surface and feed rate greatly affect the resulting weld geometry. S235 grade steel has been used. The operating equipment was a Trumpf 4001 4 kW disk laser with a diameter of 100 microns optical fiber. The effect of different welding parameters were evaluated from the metallographic cross-section of the welded joints. This article describes the effect of the different laser beam focusing and the welding feed rate.

Failure Analysis Strategies for Multistacked Memory Devices with TSV Interconnects

In this paper we will demonstrate new approaches for failure analysis of memory devices with multiple stacked dies and TSV interconnects. Therefore, TSV specific failure modes are studied on daisy chain test samples. Two analysis flows for defect localization implementing Electron Beam Induced Current (EBAC) imaging and Lock-in-Thermography (LIT) as well as adapted Focused Ion Beam (FIB) preparation and defect characterization by electron microscopy will be discussed. The most challenging failure mode is an electrical short at the TSV sidewall isolation with sub-micrometer dimensions. It is shown that the leakage path to a certain TSV within the stack can firstly be located by applying LIT to a metallographic cross section and secondly pinpointing by FIB/SEM cross-sectioning. In order to evaluate the potential of non-destructive determination of the lateral defect position, as well as the defect depth from only one LIT measurement, 2D thermal simulations of TSV stacks with artificial leakages are performed calculating the phase shift values per die level.

Resistance Spot Welding (RSW) Evaluation of 1.0 mm Usibor® 1500 P to 2.0 mm Usibor® 1500 P Steel for Automotive Body Structure Applications

There has been a substantial increase in the use of advanced high strength steel (AHSS) in automotive structures in the last few years. The usage of these materials is projected to grow significantly in the next 5–10 years with the introduction of new safety and fuel economy regulations. AHSS are gaining popularity due to their superior mechanical properties and use in parts for weight savings potential, as compared to mild steels. These new materials pose significant manufacturing challenges, particularly for welding and stamping. Proper understanding of the weldability of these materials is critical for successful application on future vehicle programs. Due to the high strength nature of AHSS materials, higher weld forces and longer weld times are often needed to weld these advanced strength steels. In this paper, the weld current lobes, mechanical properties (shear tension and cross tension), metallographic cross-section and microhardness profile of 1.0 mm Usibor® 1500 P and 2.0 mm Usibor® 1500 P joint in a two-metal stackup are discussed. Weld lobes were developed with Medium Frequency Direct Current (MFDC) equipment, ISO-type B16 tips, weld force of 3.42 kN and hold time of 5 cycles. The weld times were varied at 12, 15 and 18 cycles, with each producing current ranges at or below 3.0 kA. Tensile shear and cross tension samples were made at weld time of 15 cycles, with samples showing average loads of 15.73 kN and 4.41 kN, respectively. Also, microhardness assessment using metallographic cross-sections were analyzed at three different weld cycles (12, 15, and 18 cycles). Voids were observed at 12 and 15 weld cycles, however there was no void at 18 cycles. Similar heat affected zones (HAZ) and weld zones were observed for three different weld cycles.

Resistance Spot Welding (RSW) Evaluation of Uncoated 1.7 mm Direct Strip Production Complex 700B (DSPC) Steel for Automotive Body Structural Applications

There has been a substantial increase in the use of advanced high strength steel (AHSS) in automotive structures in the last few years. The usage of these materials is projected to grow significantly in the next 5–10 years with the introduction of new safety and fuel economy regulations. AHSS are gaining popularity due to their superior mechanical properties and use in parts for weight savings potential, as compared to mild steels. These new materials pose significant manufacturing challenges, particularly for welding and stamping. Proper understanding of the weldability of these materials is critical for successful application on future vehicle programs. Due to the high strength nature of AHSS materials, higher weld forces and longer weld times are often needed to weld these advanced steels. In this paper, the weld current lobes, mechanical properties (shear tension and coach peel), metallographic cross-section and microhardness profile of uncoated Direct Strip Production Complex 700B (DSPC 700B) 1.7 mm steel welded to itself in a two-metal stackup are discussed. Weld lobes were developed with Medium Frequency Direct Current (MFDC) equipment, ISO-type B20 tips, weld force of 5.78 kN and hold time of 5 cycles. The weld times were varied at 19, 24 and 29 cycles, with each producing current ranges at or below 4.0 kA. Tensile shear and coach peel samples were made at weld time of 19 cycles, with samples showing average loads of 18.38 kN and 3.14 kN respectively. Also, microhardness assessment using metallographic cross-sections were analyzed at three different weld cycles (19, 24 and 29 cycles). Similar heat affected zones (HAZ) and weld zones were observed for three different weld cycles.

Resistance Spot Welding Evaluation of Complex Phase 780 (CP780) Steel for Automotive Body Structural Applications

The usage of advanced high strength steel (AHSS) in automotive body structures is projected to grow significantly in the next 5–10 years with the introduction of new safety and fuel economy regulations. This is due to their superior mechanical properties and weight savings potential. These new materials pose significant manufacturing challenges, particularly for welding and stamping. Due to the high strength nature of AHSS materials, higher weld forces and longer weld times are often needed to weld these advanced steels. In this paper, the weldability of Complex Phase 780 (CP780) is discussed in terms of weld current lobes, mechanical properties (shear and cross tension), metallographic cross-section and micro-hardness profile of 1.4 mm electro-galvanized (EG) steel welded to itself in a two-metal stack-up Weld lobes and a full factorial Design of Experiment (DOE) was conducted.

Evaluation of Al2O3 MOCVD Coating for Titanium Alloys Protection under Severe Conditions at High Temperature

The corrosion resistance of MOCVD Al2O3 coating system was investigated to protect a TA6V Alloy under hot salt corrosion conditions: This coating was corroded with a salt deposit without mechanical loading at 480°C during 100 h. Corrosion products formed in salted areas were studied by Energy Dispersive Spectroscopy (EDS). Although all coated specimens were damaged with corrosion products presence in salted area, Al2O3 coatings showed the lowest salt damage on titanium substrate after a metallographic cross section observation compared to uncoated ones. As well as these interesting experimental results, coated specimens exhibit a good adherence on titanium substrate

Corrosion Product Identification by Micro-Raman and Mossbauer Spectroscopy

Micro-Raman spectrometry and Mossbauer spectroscopy have been used to identify the corrosion products on a steel coupon exposed in an industrial environment for 16 years. The Raman analysis was performed on a polished metallographic cross-section in order to map the oxides across the thickness of the coating. The spectra were recorded using a LabRam Micro-Raman spectrograph incorporating a 17 mW HeNe laser (attenuated to 1 mW to prevent oxide transformation), focused to 1 μm spot size, and 1800 g/mm grating. The confocal line-scan imaging enabled 100 spectra to be recorded in one scan at 0.5 um intervals across the thickness of the coating. The Mossbauer analysis was performed using in-situ scattering Mossbauer spectroscopy on the attached corrosion coating and transmission Mossbauer spectroscopy at 300K and 77K on the removed coating, to measure the fraction of each oxide present. Micro-Raman spectrometry showed that the corrosion products had formed in distinct layers as shown in Figure 1.