Halil Karakoç

Effect of the B4C reinforcement ratio on surface roughness of A16061 based metal matrix composite in wire-EDM machining

This study investigates the machining properties of Al6061 reinforced with boron carbide (B4C) and the effect of cutting parameters on surface roughness in wire electrical discharge machining of (WEDM). Four Al 6061 metal matrix composites reinforced with 5 wt%, 10 wt.%, 15 wt.%, and 20 wt.% B4C were fabricated by powder metallurgy. Influence of the B4C reinforcement particles on surface roughness were studied during the WEDM. Experiments were conducted based on Taguchi L18 (21 × 32) with a mixed orthogonal array and the optimal machining parameters were investigated for the surface finish. The machining parameters were analyzed by using main effect graphs and analysis of variance (ANOVA). The results showed that the reinforcement particles were uniformly dispersed in matrix structure and the surface quality of machined specimens were improved with increasing the weight fraction of the B4C reinforcement. The best surface roughness values were measured at lower peak current (IP) and surface quality of the machined part was decreased with increasing peak current.

Fabrication of AA6061/B4C composites and investigation of ballistic performances

In this study, mechanical properties of B4C particulate reinforced AA6061 matrix composites produced by powder metallurgy were investigated and their ballistic performances were examined. AA6061 matrix particles have been mixed with B4C particle for 45 minute and cold pressed under 400 MPa. The pressed compacts have been sintered at 550oC for one hour, and then were extruded at the same temperature. In order to improve rigidity, the T6 precipitation processes were applied to the composite samples. The ballistic performance of composite samples against 7.62×51 mm shootings were examined. Extruded plate samples have shown significantly high ballistic performance against 7.62×51 mm shootings. It is proved that the ballistic performance is increasing by using dual plate composite system against 7.62×51 mm shootings.

Mechanical and ballistic properties of powder metal 7039 aluminium alloy joined by friction stir welding

Abstract 7039 Al alloy plates which were used as armor materials were produced by powder metallurgy method. The prepared mixed powders were pressed and plated by extrusion process. These plates, after being subjected to T6 heat treatment, were joined double-sided by friction stir welding method. Microstructure and microhardness of the welded plate were investigated. It was determined that the finest grain structure and the lowest hardness value occurred in the stir zone as 2–6 μm and HV 80.9, respectively. In order to determine the ballistic properties of welded plates, 7.62 mm armor piercing projectiles were shot to the base metal (BM), heat affected zone (HAZ), and thermomechanically affected zone+stir zone (TMAZ+SZ). Ballistic limits ( v 50 ) of these zones were determined. The ballistic limits of the BM, TMAZ+SZ, and HAZ of the plate were approximately 14.7%, 15.3%, and 17.9% lower than that of the standard plate at the same thickness, respectively. It was determined that the armor piercing projectiles created petaling and ductile hole enlargement failure types at the armor plate. Ballistic and mechanical results can be enhanced by hot–cold rolling mills after extrusion and particle reinforcement.

Investigation of mechanical properties of tubular aluminum foams

Abstract This manuscript focuses on the mechanical behavior under compressive and bending loadings of tubular aluminum foams. The tubular structures were manufactured using the powder metallurgy technique. Tubular aluminum foams were fabricated by heating foamable precursor materials above their melting temperature in a mould. The influence of important parameters such as wall thickness and density of foam on the mechanical properties was investigated. It was found that the 6 mm thick specimen showed a lower collapse strength than the thicker 9 mm specimen. Despite the decrease in densities of the samples, the collapse strength increased with the increase in wall thickness. The reduction of approximately 33% in wall thickness (from t = 9 mm to 6 mm) decreased the bending performance of the tubular aluminum foams by approximately 50%.

TOZ METALURJİSİ YÖNTEMİYLE ÜRETİLEN AlSi7 KÖPÜKLERİN DÜŞÜK HIZLI DARBE ENERJİLERİ ALTINDA PENETRASYON DAVRANIŞININ İNCELENMESİ

Bu calismada AlSi7 kopuklerin dusuk hizli darbe enerjileri altindaki penetrasyon davranislari incelenmistir. Bu amacla toz metalurjisi yontemi ile uretilen 55x55x20 mm boyutlarinda Al kopuklere agirlik dusurme test cihazi kullanarak farkli hizlarda (1,2 - 3 ms -1 ) darbeler uygulanmistir. Bir numune uzerinde delinme meydana gelene kadar yapilan darbe testleri ile saplanma ve delinme darbe davranislari incelenmistir. Darbe sonrasi numunelerin icyapilarinda meydana gelen degisiklikler makro boyutta incelenmistir.