An investigation of mechanical properties of Ti6Al4V produced by additive manufacturing (AM) in the as-printed condition have been conducted and compared with wrought alloys. The AM samples were built by Selective Laser Melting (SLM) and Electron Beam Melting (EBM) in 0°, 45° and 90°—relative to horizontal direction. Similarly, the wrought samples were also cut and tested in the same directions relative to the plate rolling direction. The microstructures of the samples were significantly different on all samples. α′ martensite was observed on the SLM, acicular α on EBM and combination of both on the wrought alloy. EBM samples had higher surface roughness (Ra) compared with both SLM and wrought alloy. SLM samples were comparatively harder than wrought alloy and EBM. Tensile strength of the wrought alloy was higher in all directions except for 45°, where SLM samples showed higher strength than both EBM and wrought alloy on that direction. The ductility of the wrought alloy was consistently higher than both SLM and EBM indicated by clear necking feature on the wrought alloy samples. Dimples were observed on all fracture surfaces.

The need to manufacture components out of copper is significantly increasing, particularly in the solar technology, semiconductor, and electric vehicle sectors. In the past few decades, infrared laser (IR) and green laser (GL) have been the primary technologies used to address this demand, especially for small or thin components. However, with the increased demand for energy saving, alternative joint techniques such as blue diode laser (BDL) are being actively explored. In this paper, bead-on-plate welding experiments on 0.2 mm thick pure copper samples employing a BDL are presented. Two sets of parameters were carefully selected in this investigation, namely Cu-1: Power (P) = 200 W; Speed (s) = 1 mm/s; and angle = 0°, and Cu-2: P = 200 W; s = 5 mm/s; and angle = 10°. The results from both sets of parameters produced defect-free full penetration welds. Hardness test results indicated relatively softer weld zones compared with the base metal. Tensile test samples fractured in the weld zones. Overall, the samples welded with Cu-1 parameters showed better mechanical properties, such as strength and elongation, than those welded with the Cu-2 parameters. The tensile strength and elongation obtained from Cu-1 were marginally lower than those of the unwelded pure copper. The outcomes from this research provide an alternative welding technique that is able to produce reliable, strong, and precise joints, particularly for small and thin components, which can be very challenging to produce.

Ti-5Al-5V-5Mo-3Cr (Ti5553) is a metastable β titanium alloy with a high potential use in the aeronautic industry due to its high strength, excellent hardenability, fracture toughness and high fatigue resistance. However, recent research shows this alloy has a limited weldability. Different welding technologies have been applied in the literature to weld this alloy, such as electron beam welding (EBW), gas tungsten arc welding (GTAW) or laser beam welding (LBW) under keyhole regime. Thus, in tensile tests, joints normally break at the weld zones, the strength of the welds being always lower than that of the base metal. In the present work, a novel approach, based on the application of LBW under conduction regime (with a High-Power Diode Laser, HPDL), has been employed for the first time to weld this alloy. Microstructure, microhardness and strength of obtained welds were analyzed and reported in this paper. LBW under conduction regime (LBW-CR) leads to welds with slightly higher values of Ultimate Tensile Strength (UTS) than those previously obtained with other joining processes, probably due to the higher hardness of the fusion zone and to lower porosity of the weld.

In the process of shale gas development, different drilling, hydro-fracturing, and pumping speeds will produce different productivity effects. This reflects the effect of the loading rate of rock mechanics. Therefore, it is of great scientific significance to study the deformation and failure characteristics of shale under different loading rates. In order to reveal the loading rate effect of the Longmaxi shale, a series of laboratory experiments were carried out, including scanning electron microscope, XRD, and uniaxial compression tests at different loading rates. The results show that 1) the peak strength and elastic modulus of shale increase with the increase in the loading rate, but Poisson’s ratio has no obvious rule with the increase in the loading rate. In contrast, the loading rate causes the peak strength to vary by about 20%, which is larger than that of the elastic modulus. 2) The loading rate has a significant influence on shale failure. A higher loading rate will lead to severe damage but with simple cracks, whereas a lower loading rate will lead to complex damage of cracks. With the decrease in the strain rate, the length of the failure crack increases greatly. Therefore, a lower strain rate is helpful to form more broken fragments in the shale matrix. 3) By analyzing the relationship between elastic strain energy/dissipated energy and the loading rate, it is found that the elastic strain rate has a preliminary increasing and then a decreasing trend with the loading rate, but the dissipated energy has a decreasing trend with the loading rate. A higher loading rate is helpful to increase the brittleness of the shale, but a lower loading rate is beneficial to forming more cracks and a greater degree of fracture in the shale matrix. The effect of the loading rate on the mechanical properties and fracture properties of the shale is discussed. It is suggested that the lower hydro-fracturing rate is useful for generating more complex crack networks in the shale reservoirs.

The need for thin foil welding is increasing significantly, particularly in the electronic industries. The technologies that are currently available limit the joining processes in terms of materials and their geometries. In this paper, a series of trials of fusion welding (bead-on- plate) of commercially pure titanium (CPTi) foils were conducted using a blue diode laser (BDL) welding method. The power used was 50 W and 100 W for 0.1 mm and 0.2 mm thick foils, respectively. Following welding, various samples were prepared to examine the weld profiles, microstructures, hardness, tensile strength, and fracture surface characteristics. The results showed that the base metal (BM) had an annealed microstructure with equiaxed grains, while the weld zones contained martensite (α’) with large grains. The hardness increased in both regions, from around 123 HV to around 250 HV, in the heat-affected zone (HAZ) and fusion zone (FZ) areas. The tensile tests revealed that the strengths of the welded samples were slightly lower than the unwelded samples, i.e., UTS = 300–350 MPa compared with 325–390 MPa for the unwelded samples. Fracture took place within the BM area. All of the samples, welded and unwelded, showed identical fracture mechanisms, i.e., microvoid coalescence or ductile fracture. The weld zone experienced very small strains (elongation) at fracture, which indicates a good weld quality.