Effect of precipitation kinetics on microstructure and properties of novel Al-Mn-Cr-Zr based alloys developed for powder bed fusion – laser beam process

This study investigates the precipitation kinetics and resulting effect on microstructure and property of a family of novel high strength Al-Mn-Cr-Zr alloys designed for powder bed fusion – laser beam process. The alloys have been shown to be printable without solidification cracking along with high supersaturation of solutes in as-printed state. Upon direct ageing, two families of precipitates namely Al-Mn and Al-Zr are observed. Al-Mn containing precipitates, which are observed in as-printed condition as nanometric precipitates decorating special regions are seen to grow preferentially at grain boundaries, which is followed by growth in bulk of the sample. A possible explanation is suggested to be a higher diffusivity at grain boundaries leading to faster growth while depleting solutes around grain boundary region quickly. The Al-Zr precipitation, which normally follows bulk precipitation is observed to co-precipitate with Al-Mn precipitates. Optimised heat treatments are seen to achieve peak hardness of 143 HV at 623 K for 24 h and 142 HV at 648 K for 14 h as compared to 102 HV in as-printed condition for one of the alloys. This overall hardening effect is attributed majorly to Al3Zr nanoprecipitates along with semi-coherent Al12Mn precipitates

Advancing novel Al-Mn-Cr-Zr based family of alloys tailored for powder bed fusion-laser beam process

Additive manufacturing coupled with modern computational tools have enabled novel alloy design possibilities to create materials for the future. One such example is the Al-Mn-Cr-Zr based family of alloys tailored for powder bed fusion-laser beam process. This alloy system has previously been shown to produce crack free samples with good precipitation hardening response and strong thermal stability up to 523\ua0K 2500\ua0h. The current study investigates modifications made to enhance the mechanical response of the alloys. It was done by creating three novel alloy variants with higher Zr and addition of Mg. Interestingly, increasing Zr independently triggered grain refinement while addition of Mg independently causes significant increase in as-printed hardness albeit causing solidification cracking. Desirable properties were achieved when both higher Zr and addition of Mg was done at the same time. As-printed hardness enhanced by 30 % from previously known as-printed hardness of 102 HV to 132 HV in one of the variants. Upon direct ageing, peak hardness of 172 HV is observed thus suggesting retention of precipitation hardening

Al–Mn–Cr–Zr-based alloys tailored for powder bed fusion-laser beam process: Alloy design, printability, resulting microstructure and alloy properties

This study introduces a family of unique Al–Mn–Cr–Zr-based aluminium alloys illustrated by two ternary and one quaternary variants. The choice of alloy compositions has created a system resistant to solidification cracking while retaining high amount of solutes in solid solution in as-printed condition. Good relative density (~ 99.5%) has been demonstrated along with microstructural study supported by X-ray diffraction to display solidification structure with nanometric precipitate formation in small amounts in as-printed condition. High levels of Mn and Cr produce significant solid solution strengthening reaching hardness of up to 102 HV in as-printed condition. Additionally, the combination of Mn, Cr and Zr is shown to be important to control precipitation strengthening upon direct ageing and coarsening resistance due to slow diffusivity. To elucidate the concept of precipitation strengthening, one set of alloys was aged at 678\ua0K between 0 and 10\ua0h and microhardness results showed that average hardness response reached 130 HV for the quarternary alloy. Graphical abstract: [Figure not available: see fulltext.

A Realistic Simulation Testbed of A Turbocharged Spark-Ignited Engine System: A Platform for the Evaluation of Fault Diagnosis Algorithms and Strategies

Research on fault diagnosis on highly nonlinear dynamic systems such as the engine of a vehicle have garnered huge interest in recent years, especially with the automotive industry heading towards self-driving technologies. This article presents a novel opensource simulation testbed of a turbocharged spark ignited (TCSI) petrol engine system for testing and evaluation of residuals generation and fault diagnosis methods. Designed and developed using Matlab/Simulink, the user interacts with the testbed using a GUI interface, where the engine can be realistically simulated using industrial-standard driving cycles such as the Worldwide harmonized Light vehicles Test Procedures (WLTP), the New European Driving Cycle (NEDC), the Extra-Urban Driving Cycle (EUDC), and EPA Federal Test Procedure (FTP-75). The engine is modeled using the mean value engine model (MVEM) and is controlled using a proportional-integral (PI)-based boost controller. The GUI interface also allows the user to induce one of the 11 faults of interest, so that their effects on the performance of the engine are better understood. This minimizes the risk of causing permanent damages to the engine and shortening its lifespan, should the tests be conducted onto the actual physical system. This simulation testbed will serve 16 as an excellent platform where researchers can generate critical data to develop and compare current and future research methods for fault diagnosis of automotive engine systems.Comment: 64 pages, 23 figures, To appear in IEEE Control System

Распространенность, применение и патологические эффекты диоксида титана

ДИОКСИД ТИТАНАКРАСИТЕЛЬ БЕЛОГО ЦВЕТААЛЛЕРГЕНЫПИЩЕВЫЕ ДОБАВКИПАТОЛОГИЧЕСКИЕ ПРОЦЕСС

Accelerated learning for wood supply managers - the next generation of on-line training tools

The Virtual Wood Supply Arena is an on-line training environment for managing roundwood purchase, production and transport in cut-to-length supply systems. The purpose of its development was accelerated training for coordination of these functions under realistic operating conditions. It offers 8- and 12-week scenarios for supplying five mills. Weekly planning is done for 10 harvesting teams and 10 trucks in a Swedish case geography while tracking mill delivery fulfillment under weekly trafficability restrictions. The purpose of this paper is to introduce the training environment and report the progression of student performance after 2 years of use in university-level training. Student teams reached full delivery fulfillment within three training runs. After familiarization during an introductory run, a complete 12-week scenario took four effective hours to complete. Delivery fulfillment increased from 82 to 95 and 100% between the first, second and third training runs. The progression of team performance included a 36% reduction of relocation distances for harvesting teams and 11% reduction of transport distances for hauling from forest to mill. By the third training run these performance levels were attained with less than 2 weeks of inventory for both the purchase bank and roadside stocks

High temperature compression of Mo(Si,Al)2-Al2O3 composites

The aim of this study was to investigate the effect on high temperature of mechanical properties of adding Al2O3 particles to polycrystalline Mo(Si,Al)2. Mo(Si,Al)2-Al2O3 composites, containing 0–25 wt% Al2O3 particles have been compression tested at 1300 \ub0C, and the microstructure after deformation was studied using electron backscatter diffraction. It was shown that even small amounts (5 wt%) of Al2O3 particles resulted in a grain-refined material through inhibition of grain growth during sintering, which lead to lower flow stresses compared to the coarse-grained Al2O3-free material. The inverse grain size effect and post-test microstructure investigations suggest that creep-like deformation mechanisms dominate in fine grained Mo(Si,Al)2-Al2O3 composites at 1300 \ub0C. In the materials containing 5–15 wt% Al2O3, the maximum stress decreased with increasing Al2O3 content. In materials with higher Al2O3 additions, the maximum stress increased with the Al2O3 addition, but did not reach the strength levels in the Al2O3-free reference material. It is suggested that the deformation behaviour is affected by electroplasticity effects as resistive heating was used. Electroplasticity contributes to the decrease in maximum stress observed in the lower Al2O3 containing materials, while this is outweighed by particle strengthening at higher Al2O3 contents

High temperature deformation of polycrystalline C40 Mo(Si,Al)2

Polycrystalline Mo(Si,Al)2 with C40 crystal structure was deformed in compression with a strain rate of 10−4 s−1 at 1300 \ub0C. The specimens were deformed to a strain of 10%–15% and showed maximum stresses around 150 MPa prior to pronounced softening. No crack formation or significant increase in porosity could be observed. Post-test microstructure analysis revealed that the material was inhomogeneously deformed on both inter- and intragranular levels. Dynamic recrystallization occurred alongside low angle grain boundary formation in highly deformed grains. Furthermore, complex intragranular deformation fields suggest that slip systems other than 21̄1̄0[0001] may be active during deformation