Interface Characteristics and Mechanical Properties of Ultrasonic-Assisted Friction Stir Lap Welded 7075-T6 Aluminium Alloy

In this work, friction stir lap welding (FSLW) and ultrasonic-assisted friction stir lap welding (UAFSLW) was applied to 6-mm-thick 7075-T6 alloy sheets using three welding tools with the same process parameters. The joint formation, microstructural characteristics, and mechanical properties of the resulting lap joints were then investigated. The results showed that ultrasonic vibration significantly promoted the flow of metal at the interface, enlarged the size of the stirred zone (SZ), and reduced the angle between the hook defect and the interface. During lap shear testing, the FSLW and UAFSLW joints fractured in a similar manner. The fracture modes included tensile fracture, shear fracture, and a mixture of both. Cold lap and hook defects may have served as crack-initiation zones within the joint. Under configuration A (i.e., upper sheet on the retreating side (RS)), all joints failed in the shear-fracture mode. The effective lap width (ELW) of the joint welded using tool T2 was the greatest. This resulted in a higher shear fracture strength. The maximum shear fracture strength of the UAFSLW joint was 663.1 N/mm. Under configuration B (i.e., upper sheet on the advancing side (AS)), the shear fracture strength was greatly affected by the fracture mode. The highest shear fracture strength of the UAFSLW joint, 543.7 N/mm, was welded by tool T3. Thus, under otherwise identical conditions, UAFSLW joints can withstand a greater fracture shear strength than FSLW joints, as ultrasonic vibration helps to mix the material at the interface, thus, enlarging the SZ and diminishing the cold lap defects.

Effect of Tool Geometry and Welding Parameters on Friction Stir Welded Lap Joint Formation with AA2099-T83 and AA2060-T8E30 Aluminium Alloys

In this paper the effect of tool geometry and welding parameters on friction stir welded lap joints with AA2099-T83 and AA2060-T8E30 aluminium alloys has been investigated through the study of the material flow and weld formation along with the reaction forces during friction stir welding (FSW) for various sets of welding parameters and two FSW tools with different geometrical features. The results showed that welding parameters and tool probe geometry strongly affect the characteristics of the typical defect features (hook and cold lap defects) of the friction stir welded lap joints. From the relationship established between the welding parameters, tool probe geometry and the hook and cold lap defect formation, some guidelines are concluded with the objective of guaranteeing appropriate FSW lap joint properties.

Feasibility and interface migration characteristics of friction stir lap welding of LA141 Mg-Li alloy

Abstract2 mm-thick LA141 plates were successfully friction stir lap welded (FSLW). The similar FSLWLA141Mg-Li alloy joint appeared a downward hook on the advanced side and an upward cold lap on the retreating side. The load of lap-shear tensile testing reached 2.8 kN, and the joints failed in the interface defects. The interface migration of LA141/LA141 lap joint during FSLW process was driven by forces at interface, such as a frictional force paralleled to the thread, a downward pressure perpendicular to the surface of the thread, the resistance from unsoftened metal and its own gravity. Moreover, the FSLWof AZ31/LA141 and LA141/AZ31 furtherly verified that forces at the interface were critical factors in determining the interface migration during FSLW process.

Numerical Simulation and Production Trial of Aluminum Alloy Gear Box Housing

Die casting processing analysis was conducted and the gating system and the cooling system were designed for aluminum alloy gearbox housings. Numerical simulation software PROCAST was used to calculate the filling and solidification sequence and the temperature field of die castings. The reasonable designs of the gating system and the cooling system were obtained. The feasible die casting mould was designed and manufactured. Production trial showed that, casting molding effect is good, and there were not defects such as misrun, cold lap. After machining, there were not defects exceeding the allowed limited values including porosity, shrinkage, and slag inclusion in the products. The trial showed that the product mold design and die casting technology achieved the desired effect, which can realize batch production.

Study on Temperature Influence on Lack of Fusion Formation in Spatter/Base Metal Interface

In the development of modern welded structures with longer life-time and/or higher load-carrying ability, fatigue properties are becoming more and more important. A lot of researches have been done to investigate which factors can elongate the fatigue life of weldments. Cold lap defects, were found to be important initiation sites of the fatigue failure in 1990s. In the ISO standard, cold lap is referred to as a type of micro-lack of fusion. Previous study found that most of the cold laps in GMAW process are formed in spatters. In this paper the interface of spatter/base metal was cut, polished and investigated by conventional metallographic methods. The aim is to reveal the influence of temperature on cold lap formation. In the experiments, different pre-heating temperatures of the parent plate were used in tandem GMAW. Results showed linear empirical relationship between the temperature of the parent plate and the amount of lack of fusion in the spatter/base metal interface.

The Exploration of Appropriate Pouring Time which is the Important Parameters in Gray Cast Iron Foundry Process Design

The determination of pouring time is the important content in the casting process design. Pouring time to determine the design of the casting process is very important content. Appropriate pouring time can avoid many defects such as misrun, cold lap, entrapped slag, distortion, blowhole, swell, cope raise and so on. This paper analyzes the characteristics and shortcomings of determining several kinds of pouring time in current production of gray iron castings. The writer proposed a new calculate formula of pouring time about gray iron casting. By comparing the successful production instances, it is proved that it is good reliability, scientific and suitability.