AZTERLAN

In recent years, there has been a significant research effort in the laser powder bed fusion (LPBF) processing of Nitinol aiming potentially for stenting applications. To achieve superelasticity that Nitinol stents require, Ni content needs to be within ±0.1at% of the optimal Ni content of 50.8at%, but the high thermal intensity of the laser in LPBF results in a Ni-loss. How to achieve the targeted Ni content in LPBF processed Nitinol alloys, whilst producing defect-free parts is not certain, requiring further evaluation. In the LPBF processing of a Nitinol powder with 51.2at% Ni herein, we exhibit defect-free processing obtaining the idealised Ni content with the use of a constant scan velocity and narrow power and thus energy (E) window. An exponential decay in Ni content with increasing E was observed and is correlated to the aspect ratio of the melt pool shape. Under optimum, defect free conditions, a primarily austenite structure with a tiny amount of twinned martensite is reported by room temperature. Sequential transmission electron micrographs taken between −80 °C to 0 °C on a defect-free sample have illustrated the transformation of twinned martensite to austenite with the major portion of the transformation taking place well below 0 °C. • Ni content of Nitinol decreases exponentially with laser energy due to Ni loss. • The loss is ~0.4at% using defect-free conditions of laser powder bed fusion. • Defect-free builds using 51.2at%Ni powder is austenitic with a trace of martensite. • Austenite-martensite transformation is a grain-by-grain event.

Abstract: Scams are systematically executed crimes. Criminal tactics are organized based on the targeted victims, timing, and technological advances. Various approaches have been implemented by authorities to educate and raise awareness among the public regarding the modus operandi and methods of self-protection against these crimes. Therefore, this study aims to identify the level of knowledge and behaviour on self protection against scam crimes among teenagers in Malaysia. A total of 482 teenagers aged 16 to 19 participated in this study. The survey instrument involved five constructs and 29 items formulated based on guidelines, campaigns, and promotional materials implemented by various authoritative agencies in Malaysia. Data were analyzed using descriptive analysis in the form of frequency, percentage, and cross tabs analysis. While the inference analysis used was the multiple regression analysis to analyze the influence of each variable toward respondents’ behaviour. The analysis results found that the scores of teenagers’ knowledge for two constructs were high (data information, data security), and three constructs were moderate (communication, digital content, problem-solving). Whereas the finding of multiple regression analysis indicated that all variables were significant in influencing respondents’ behaviour except for the digital content variable. Overall, this study proved that the protective actions taken by authorities against scam crimes were effective. However, these efforts need to be continued to ensure that these preventive elements can still be practiced in the future. Keywords: Scam; Teenagers; Communication; Digital Content; Problem-solving; Data Security; Data Information

The combination of wrought materials and laser-based directed energy deposition (DED-LB) is being increasingly used for manufacturing new and repairing old or damaged components in several industries. Aerospace components made of Inconel 718 featuring small-thickness DED-LB buildups are a remarkable example of such a combination due to the high added value it brings. Despite that these are usually critical components, the miniature testing methods to assess the local mechanical properties in the buildup area are not fully developed. This work contributes to this miniature testing development with an improvement of the small punch testing (SPT) technique for measuring the mechanical properties of the weld line between the DED-LB and the wrought substrate. A new criterion for weld line positioning in the SPT specimens is proposed and applied on samples of hybrid wrought/DED-LB Inconel 718. The results of positioning the weld line at the necking site of the SPT specimen show that the proposed approach is valid for assessing the properties of the transition zone between the wrought and additive states. For the specific conditions tested and taking the wrought material as a reference, the strength of the Inconel 718 drops 10% in the weld line and 20% in the buildup.

Scalmalloy is an Al–Mg alloy with additions of Sc and Zr originally developed as a high‐strength aluminum alloy with σ0.2 ≥ 450 MPa for aerospace industry. It is now well understood that the alloy is amendable for processing by laser powder bed fusion (LPBF). However, the mechanism of formation of the equiaxed‐columnar bimodal grain structure during LPBF is not ascertained yet, fully. Herein, this gap is addressed with special focus on the distributions of critical elements such as Sc and various particles that form during LBPF. It is found that strong and weak segregation of Mg and Sc, respectively, occurs in the final solidification areas of the fine‐ and equiaxed‐grain regions. The coarser and columnar grain regions show weak segregation of Mg and no Sc segregation. A priori knowledge on the Al–Sc eutectic reaction, its dependence on cooling rates, and the well‐known thermal and solidification conditions related to the track location during LPBF is used to ascertain the mechanism of formation of the bimodal grain structure. The mechanism suggested is substantiated by the location‐dependent elemental distributions and the various particles that are observed.

The determination of silicon and carbon contents by thermal analysis is based on the recording of a cooling curve of a melt whose eutectic solidification takes place in the metastable system. The temperatures of the austenite and eutectic arrests are evaluated and then related to the carbon and silicon contents by linear relationships that would be defined by the phase diagram if there were no undercoolings. However, published experimental values of austenite liquidus arrest and metastable eutectic arrest both show significant undercoolings when compared to the equilibrium metastable Fe–C–Si phase diagram. The undercooling of the austenite observed in hypo-eutectic alloys can be explained by tip undercooling during dendritic growth. On the other hand, it is pointed out that alloys with a composition close to the stable eutectic—either slightly hypo- or slightly hypereutectic—can show much higher undercoolings than expected if some stable eutectic precipitates. For such compositions, the thermal analysis could hardly be reproducible enough if the alloy does not solidify completely in the metastable system. Furthermore, the published experimental information on the temperature of the metastable eutectic is here supplemented by new results for silicon contents up to nearly 4 wt%. Both previous and new results show a similar undercooling of 5 to 15 °C compared to the calculated equilibrium metastable eutectic. Each foundry wishing to use thermal analysis for carbon and silicon evaluation must determine its own relationships for austenite liquidus and metastable eutectic to account for the specificity of its melting process and casting system. Care should be taken to avoid any graphite precipitation in the thermal cup, and testing should be performed to improve reproducibility as this defines the accuracy of the composition determination.