Recently, 316L stainless steel fabricated by selective laser melting (SLM) has been widely used in various fields; however, the influence of post-processing heat treatments on its corrosion resistance has not yet been fully clarified in the literature. In this study, the corrosion behavior of SLM-built 316L stainless steel is investigated in its as-built state and after various heat-treatments, and the results are compared with those of conventionally processed (wrought) 316L. Electrochemical measurements show that the SLM-manufactured specimens exhibit lower corrosion resistance than their wrought counterparts. Furthermore, neither stress-relief annealing at 650 °C nor solution (recrystallization) treatment at 1050 °C leads to a measurable improvement in the corrosion resistance of the SLM-manufactured material under the conditions investigated.
This study investigates the effect of different cooling media during heat treatment on the microstructure and mechanical properties of SUP9 spring steel. The study focused on correlating microstructural evolution with microhardness and analytically predicting tensile properties. The specimens of the SUP9 spring steel were austenitized at 1000 °C for 1 hour and cooled with various media such air, oil, water, brine solution, and ice. The normalized specimens showed lower microhardness and mechanical strength because of stress relief and relatively coarse microstructures. On the other hand, increasing the cooling rate promoted the formation of refined lath martensite, which resulted in significant improvements in microhardness and estimated tensile properties. The maximum microhardness of 340 HV and 286 HV was observed in pearlitic and ferritic regions, respectively, due to the effect of ice quenching, which also resulted in the maximum yield strength ( YS ) and ultimate tensile strength ( UTS ) values of 967.49 MPa and 1086.37 MPa. Also, the properties of brine quenching were better than the standard water quenching. The results gave detailed microstructure-property correlation for different quenching conditions. This comprehensive microstructure-property correlation can be exploited to optimize the mechanical performance of spring steels for advanced engineering applications.
Due to the increasing applicability of short fiber-reinforced thermoplastic composites in numerous industrial applications, it is essential to develop efficient models for assessing and predicting their fatigue life for optimal design and operation of components made of these materials. Due to material heterogeneity and complex fatigue response that covers not only mechanical fatigue but also the self-heating effect, i.e. dissipative heating coupled with mechanical response, the fundamental understanding of fracture and failure mechanisms driven structural degradation of these materials is of key importance. In this study, the progression of fatigue damage under fatigue loading has been evaluated with the presence of the self-heating effect and specific fracture mechanisms have been identified using X-ray computed tomography. The character and rate of progression of fatigue damage are reported together with specific fracture mechanisms for thermomechanical fatigue loading.
This study investigates the strength degradation processes of structural glass-fiber reinforced plastics (GFRP) under transient heating, simulating standard fire conditions. A comparative analysis of the thermomechanical behavior of composites based on a traditional bromine-containing epoxyphenolic binder and a modified system based on epoxidized dinaphthol was conducted. It is established that at temperatures exceeding the glass transition temperature of the polymer matrix, the classic Zhurkov thermofluctuational equation becomes inapplicable due to complex phase and structural transformations in the material. It is proven that the use of oligomers with conjugated aromatic rings allows for significantly slowing down the degradation process and retaining up to 60% of the initial strength of the GFRP due to intensive pyrolytic transformations and the formation of a carbonized protective layer. Additionally, the effect of the free cooling stage on the residual load-bearing capacity of the materials is evaluated. It is shown that GFRPs based on epoxidized dinaphthols retain from 20 to 45% of their residual strength (depending on the type of loading) after the cessation of heat exposure in the fire regime and the free cooling of the material.
A desirable property in metal applications for medical, aerospace, and automobile applications is low weight, impact strength, wear resistance, and high strength. Titanium (Ti) and aluminum (Al) are lightweight, only titanium possesses some of these properties. However, to achieve improved properties, Ti-Al binary alloys are used as base metals, but with synthetic and natural reinforcements. In this study, zirconium oxide (ZrO2) and rice husk ash (RHA) in different proportions were combined with aluminum alloy (Al6061), proportions of titanium and aluminum powder to form novel metal matrix composites. Four sets of samples of varying weight fractions of Ti, Al, with each having six (6) samples with varying fractions of RHA and ZrO2, making a total of twenty-four (24) samples, were fabricated through the stir casting process. Tensile tests were carried out on each sample to determine its mechanical properties. The weight fraction by per cent of Al6061 was 85% for all the samples. From the tensile test, Ti increases the strength of the sample more than Al powder. For both tensile and ductile properties, RHA has a better impact on the modulus of elasticity than increased ZrO2 reaching as high as 152 MPa. However, it can be proven that Ti powder, Al powder, RHA, and ZrO2 all improved the mechanical properties of Al6061.
