Muzaffer Zeren

Influence of Cu addition on microstructure and hardness of near-eutectic Al-Si-xCu-alloys

The influence of Cu content on the microstructure and hardness of near-eutectic Al-Si-xCu (x = 2%, 3%, 4% and 5%) was investigated. After melting Al-based alloys with different Cu contents, alloys were cast in green sand molds at 690 °C and solidified. The solution treatment was performed at 500 °C for 7 h and then the specimens were cooled by water quenching. The samples were respectively aged at 190 °C for 5, 10 and 15 h to observe the effect of aging time on the hardness of matrix. Also differential thermal analysis was used to obtain the transition temperature of the equilibrium phases at cooling rate of 30 K/min and to determine the effect of Cu content on the formation of quaternary eutectic phases and the melting point of α(Al) + Si. The results show that as Cu content in the alloy increases, the hardness of matrix increases due to precipitation hardening, the melting point of α(Al) + Si decreases and the amount of these eutectic phases increases, quaternary eutectic phase with melting point of 507 °C forms when Cu content is more than 2%.

Effect of Cu content on the corrosion of Al‐Si eutectic alloys in acidic solutions

Purpose – The purpose of this paper is to understand corrosion behavior of different Cu‐containing Al‐Si‐x% Cu alloys (x: 1 wt% Cu, 2 wt% Cu, 3 wt% Cu, 4 wt% Cu, and 5 wt% Cu) in 0.1 M HCl and 0.1 M H2SO4.Design/methodology/approach – Potentiodynamic, chronoamperometric and impedance measurements were applied to specimens to obtain their electrochemical characteristics. For the long‐term analyses, hydrogen evolution with immersion time (V‐t) was measured. The corroded surfaces of the alloys were investigated using scanning electron microscopy (SEM) to understand the corrosion mechanism.Findings – All experimental investigations showed that the corrosion resistance of alloys increased with increasing Cu content in the alloys.Research limitations/implications – Cu‐containing aluminum alloys are age‐hardenable alloys. The corrosion behaviour of these alloys can be changed by heat treatment. Corrosion test results for the heat treated and aged alloys will be discussed in another study.Originality/value – Al‐S...

Evaluation of cyanoacrylate augmentation of transpedicular screw pullout strength

Purpose: Pedicle screw fixation of osteoporotic bone in the elderly is a challenge. Various augmentation methods have been studied by many authors. Although polymethylmethacrylate (PMMA) augmentation is believed to be a standard method, its usage is fraught with complications. Butyl-2-cyanoacrylate is an alternative to PMMA as it is bioresorbable, biocompatible, inexpensive, and noninfective. The objective of the current study was to determine the pullout strength of the pedicle screws when butyl-2-cyanoacrylate is used for augmentation. Methods: Fresh calf lumbar vertebrae were obtained from male calves weighing 100-120 kg and implanted with pedicle screws. The screws were placed in native, unaugmented bone (group 1), butyl-2-cyanoacrylate-augmented bone (group 2), and PMMA-augmented bone (group 3). Axial pullout tests were done by an Instron 4411 universal testing machine. Statistical analysis was performed using the SPSS 9.0 for Windows program. Paired samples t test was used, and P < 0.05 was considered significant. Results: The mean bone mineral density of the vertebrae was 1.6 ± 0.1 g/cm2. The mean pullout strengths were 1.55 ± 0.23 kN for group 1, 1.62 ± 0.42 kN for group 2, and 2.55 ± 0.22 kN for group 3. There was no statistically significant difference between groups 1 and 2. PMMA augmentation increased the pullout strength significantly when compared with butyl-2-cyanoacrylate augmentation and native bone (P = 0.002 and P = 0.001, respectively). Conclusions: The results of this study show that butyl-2-cyanoacrylate has no contribution to the augmentation of pedicle screw fixation in a calf model when compared with native bone or PMMA augmentation. Further studies are required to evaluate the effectiveness of butyl-2-cyanoacrylate in osteoporotic specimens and under cyclic loading in calf vertebra and animal and cadaver models before dispensing with its utility as an augmentation method in the clinical setting.

The microstructural design of diamond cutting tools

The use of diamond tools has, over recent years, become widely accepted as the most economical method of processing natural stone. The ever-increasing pressure for higher production rates and better surface textures in finished stone products has resulted in diamond cutting becoming one of the major growth areas in the stone industry of Turkey. In this study, a general defect characterization in the continuous disc type diamond cutting tools used in marble, granite, and natural stone cutting has been investigated. Transverse rupture tests were carried out with different matrix and diamond compositions. The toughness of the tested materials was determined.

Microstructural chracterisation of Al-Si-xTi cast alloys

Abstract The present paper reports the existence and morphology of intermetallic particles in Al–Si–xTi cast alloys. Near eutectic Al–Si alloys with 0, 0·1, 1, 2, and 5% Ti have been utilised for this purpose. Metallographic observations were made by the combination of an optical microscope and a scanning electron microscope. Wear tests were performed in a pin on disc tribometer under dry sliding conditions. The addition of Ti to the Al–Si alloys led to the precipitation of TiAlSi intermetallic phase. By increasing Ti content, hardness increases due to increasing volume fraction of relatively hard intermetallics.

Effect of heat treatment on erosive wear behaviour of Ti6Al4V alloy

Abstract In this paper, the erosive wear behaviour of Ti6Al4V alloy depending on various heat treatment conditions was evaluated. It is aimed to understand the relationship between the microstructure and the erosion rate of Ti6Al4V alloys. Furthermore, the hardness and the surface morphology variations depending on the annealing parameters and the effects of these parameters on the erosion behaviour of the annealed Ti6Al4V alloy were also considered. Moreover, eroded surfaces of samples were examined by using a scanning electron microscope in order to understand dominant material removal mechanisms depending on the annealing parameters. Results showed that the aging process has dramatically affected the erosion resistance of Ti6Al4V alloy. The microstructure and the hardness of the samples have significantly affected the erosion resistance of the alloy. Surprisingly, erosion resistance decreased when the hardness increased. Finally, SEM investigations of the eroded surfaces of the heat treated samples showed that microcutting and microploughing were the dominant erosion mechanisms occurred during the erosion process.

Microstructural investigation of as cast and PREP atomised Ti–6Al–4V alloy

Abstract A microstructure characterisation of Ti–6Al–4V is conducted for cast, extruded and micrometre sized particles. The plasma rotating electrode process is used to produce spherical Ti–6Al–4V powders from an alloy electrode. The process parameters and their impact on the material properties are described. The effects of electrode rotation speed on the particle size distribution, particle shape and crystal structure are investigated in detail. Optical microscopy and scanning electron microscopy are used for microstructural characterisation. The analysis shows that cast and extruded Ti–6Al–4V alloys have equiaxial α and α+β phase structures, while plasma rotating electrode processed powder from the same alloy compositions has an acicular or martensitic (α) structure. The microstructure scale depends on the particle size. Microhardness measurements are used to assess mechanical property dependence on the microstructure of this alloy. The rapidly cooled alloy particles have much higher hardness than cast or extruded bulk alloy.

The property optimization of diamond-cutting tools with the help of micro-structural characterization

Abstract In this study, a general defect characterization in diamond-cutting tools used in marble, granite and natural stone cutting has been investigated. An important factor determining the performance of the PCD tool and the quality of the cutting operation is the bond characteristic obtained during hot pressing as a function of the pressure, sintering temperature and time. Successful diamond tool design starts with the appropriate choice of high-quality matrix powders and diamonds. The matrix should support the diamond particles without damaging them. During cutting the matrix is expected to wear to some extent provided the tips of the diamond particles run easily and also chip flow smoothly. The bond reaction of the diamond surface and surrounding metal matrix is effective for efficient tool performance. With this type of cutting/abrasive material produced by the PM techniques the primary important factor for their properties is cleanness (cleanness of operation media, cleanness of powders and diamonds used). In general, a weak diamond–matrix bond as well as oxide films and inclusions in the matrix overtake the role of crack initiation. Also the diamond particles can act as defects through their size, form and area distribution (clustering). In this study for a micro-structural optimization, the defect characterization should be realized primarily. Transverse rupture tests which are generally used for hard material were carried out with different matrix and diamond compositions. The toughness of the tested materials were determined and the defects leading to crack formation are classified.

Effect of nickel on microstructure and wear behaviour of pure aluminium against steel and alumina counterfaces

Abstract In this study, aluminium–nickel alloys with different Ni ratios ranging from 1 to 5 wt-% were produced by casting method. The effect of nickel on the microstructure and hardness properties was studied. The dry sliding wear response of the Al–xNi alloys against steel and alumina counterfaces was investigated. Worn surfaces of the alloys were examined using scanning electron microscopy. The results showed that the hardness of the alloys increases with increasing nickel content. Severe wear damage was observed at low and high nickel contents. Maximum wear resistance was obtained with the addition of 3 wt-% nickel to the pure aluminium under both loads and against both counterfaces.

Effect of heat treatment conditions on microstructure and wear behaviour of Al4Cu2Ni2Mg alloy

Al4Cu2Ni2Mg alloy is an age-hardenable aluminum alloy. The effect of different solution and aging heat treatment conditions on the microstructure, hardness and wear resistance of the alloy was studied. The cast specimens were solution treated and then artificially aged. Optical microscopy and scanning electron microscopy were used to investigate the microstructures of the specimens. The hardness and wear tests were applied to understanding the effects of heat treatment. After aging for 8 h, the hardness of the alloy increases from HV10 96.5 to 151.1. Aging treatment for a longer duration causes a drop in the hardness because of over aging. Increasing the hardness of the alloy increases the wear resistance. As a result of all tests, solution heat treatment at 540 °C for 8 h and aging at 190 °C for 8 h were chosen for optimum heat treatment conditions for this alloy.