ABSTRACT
The paper presents the analysis of two compaction methods for obtaining W/Cu Functional Graded Materials (FGMs) consisting of three layers with the following compositions (% weight): first layer 80 W/20 Cu, second layer 75 W/25 Cu, and third layer 65 W/35 Cu. Each layer composition was obtained using powders obtained through mechanical milling. The two compaction methods were Spark Plasma Sintering (SPS) and Conventional Sintering (CS). The samples obtained after the SPS and CS were investigated from morphological (scanning electron microscopy-SEM) and compositional (energy dispersive X-ray spectroscopy-EDX) points of views. Additionally, the porosities and the densities of each layer in both cases were studied. It was found that the densities of the sample's layers obtained through SPS are superior to those obtained through CS. The research emphasizes that, from a morphological point of view, the SPS process is recommended for W/Cu-FGMs, having raw materials as fine-graded powders against the CS process.
ABSTRACT
Ti-based alloys are an important class of materials suitable especially for medical applications, but they are also used in the industrial sector. Due to their low tribological properties it is necessary to find optimal technologies and alloying elements in order to develop new alloys with improved properties. In this paper, a study on the influence of sintering treatments on the final properties of a titanium alloy is presented. The alloy of interest was obtained using the powders in following weight ratio: 80% wt Ti, 8% wt Mn, 3% wt Sn, 6% wt Aluminix123, 2% wt Zr and 1% wt graphite. Two sintering methods were used, namely two-step sintering (TSS) and multiple-step sintering (MSS), as alternatives to conventional sintering which uses a single sintering dwell time. Evolution of sample morphology, composition and crystalline structure with sintering method was evidenced. The lower values for the friction coefficient and for the wear rate was attained in the case of the sample obtained by TSS.
ABSTRACT
Traumatic brain injury (TBI) represents a public healthcare problem and a major economic burden, all over the world. It is estimated that every year, on the globe, there occur about two million severe TBI and over 42 million mild TBI. The main causes of TBI in civil population are fallings, followed by car accidents. In the last decades, the accelerated development of car industry and the poor development of traffic infrastructure in low- and average-income countries led to an increasing number of brain injuries, this becoming a major problem for medical health systems. According to some studies, approximately 1.35 million people die every year because of car accidents. In the last four decades, these types of injuries started to be studied in order to understand the lesion mechanisms for developing new safety equipment that may be installed on vehicles. The device presented by us for causing a TBI in a lab rat (mechanical pendulum) allows the performance of several major types of TBI, according to the kinetic energy, exposure area, contact surface, etc. The impact energies obtained by the device we presented may vary on a large scale, from less than 1 J up to 10 J, according to its weight, launching angle and impact head shape, thus being obtained minor, moderate or severe TBI.