Additive manufacturing (AM) has become increasingly important over the last decade and the quality of the products generated with AM technology has strongly improved. The most common metals that are processed by AM techniques are steel, titanium (Ti) or aluminum (Al) alloys. However, the proportion of magnesium (Mg) in AM is still negligible, possibly due to the poor processability of Mg in comparison to other metals. Mg parts are usually produced by various casting processes and the experiences in additive manufacturing of Mg are still limited. To address this issue, a parameter screening was conducted in the present study with experiments designed to find the most influential process parameters. In a second step, these parameters were optimized in order to fabricate parts with the highest relative density. This experiment led to processing parameters with which specimens with relative densities above 99.9% could be created. These high-density specimens were then utilized in the fabrication of test pieces with several different geometries, in order to compare the material properties resulting from both the casting process and the powder bed fusion (PBF-LB) process. In this comparison, the compositions of the occurring phases and the alloys’ microstructures as well as the mechanical properties were investigated. Typically, the microstructure of metal parts, produced by PBF-LB, consisted of much finer grains compared to as-cast parts. Consequently, the strength of Mg parts generated by PBF-LB could be further increased.
Niobium is an important material for high temperature applications, in space, in superconductors or in chemical process constructions. Laser-based powder bed fusion of niobium (PBF-LB/M/Nb) offers new opportunities in design, though it is still an expensive technique. The build-up rate is an important factor for economical manufacturing using PBF-LB/M/Nb. It is largely influenced by variation of process parameters, affecting the heat flow during the manufacturing process. In this work, an empirical model for PBF-LB/M/Nb is developed. Based on this model, manufacturing parameter sets using different volume build-up rates are predicted and confirmed. They enable the manufacture of parts with homogeneous and crack-free microstructure with more than 99.9% relative density. Tensile and hardness tests of specimens, which were manufactured using different parameter sets, are performed to determine the effects of the build-up rate—and thus the heat flow during manufacturing—on different mechanical properties. The ultimate tensile strength and yield strength of as-manufactured specimens reach values up to 525 MPa and 324 MPa, respectively, while the elongation at break ranges between approximately 8 and 16%. The Vickers hardness of all specimens was in the range of 149 ± 8 HV0.1. In addition, the microstructure of the manufactured samples is investigated by means of light as well as scanning electron microscopy.
The performance of small and medium scale enterprises (SMEs) plays a key role in the growth and development of any economy. Competitive Aggressiveness (CA) has been identified as instrumental to enhancing the control of sizable market share. However, lack of adoption of this important tool has been a challenge for these SMEs leading to decline in performances. The study hence, examined the effect of competitive aggressiveness on the market share of SMEs in Lagos, Nigeria. The study adopted cross-sectional survey research design. The population comprised 8,396 owner/managers of SMEs. The Research Advisors table was used to determine a sample size of 481. A validated questionnaire was administered to 481 respondents for data collection purpose but 430 came back correctly and were used for the study. The Cronbach’s alpha reliability coefficients of the constructs ranged from 0.71 to 0.84. The response rate was 89%. Data were analyzed using descriptive and inferential statistics. Findings revealed that Competitive aggressiveness does not have a significant effect on the market share of selected small and medium scale enterprises in Lagos state (β = 0.009, R = 0.015 R2, = 0.000, F(1, 428) = 0.100, p >0.05). The study concluded that Competitive aggressiveness does not have a significant effect on market share of small and medium scale enterprises in Lagos State, Nigeria. The study recommended that firms should intensify aggressive competitive effort by working smart, carrying employees along, effective bench marketing, and proper monitoring of operational activities by regulatory bodies. These activities if well executed will increase level of market share of the SMEs in Lagos State, Nigeria.
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