Recent research and progress of biodegradable zinc alloys and composites for biomedical applications: Biomechanical and biocorrosion perspectives.

Wear behavior of Al-Mg-Cu-based composites containing SiC particles

Properties of Cu–Cr–Zr alloy with ultrafine-grained (UFG) structure produced by equal-channel angular pressing (ECAP) via different routes have been investigated. Special attention was paid to the optimization of multi-functional structural, thermal, electrical and mechanical properties of the alloy by aging of UFG one. Multi-pass ECAP via different routes gives rise to the formation of a deformation-induced submicrocrystalline structure with the grain (subgrain) sizes in the range of 200–300 nm depending on applied routes which leads to high hardness and strength in the Cu–Cr–Zr alloy with reduced ductility. Amongst the applied routes, route-Bc was found to be the best processing path for achieving the lowest grain size, the highest hardness and strength. Aging of 8Bc-processed UFG samples increases the hardness and strength of Cu–Cr–Zr alloy while retaining an electrical conductivity comparable to that of aged coarse-grained (CG) one. A satisfactory electrical conductivity of 71%IACS without considerable loss of peak hardness was achieved after aging of 8Bc-processed UFG alloy at 425 °C for 240 min. The precipitation strengthened UFG alloy remains its stable behavior at elevated temperatures up to 450 °C.

Optimization of strength, ductility and electrical conductivity of Cu–Cr–Zr alloy by combining multi-route ECAP and aging

Dry sliding wear behaviour of Al–12Si–4Mg alloy with cerium addition

Microalloyed Zn-Mn alloys: From extremely brittle to extraordinarily ductile at room temperature

Effect of copper content on the mechanical and sliding wear properties of monotectoid-based zinc-aluminium-copper alloys

One binary Zn–15Al, five ternary Zn–15Al–Cu and six quaternary Zn–15Al–3Cu–Si alloys were prepared by permanent mold casting. Their microstructures and mechanical properties were investigated using metallography and hardness, tensile, compression and impact tests. The microstructure of the binary Zn–15Al alloy consisted of β dendrites and α and η phases. The microstructure of ternary Zn–15Al–Cu alloys containing more than 2% Cu revealed e (CuZn4) particles in addition to the phases present in the binary alloy and the quaternary Zn–15Al–3Cu–Si alloys exhibited silicon particles in addition to the phases present in the ternary alloys. The hardness and compressive strength of these alloys increased continuously with increasing copper and silicon contents. Their tensile strength also increased with increasing copper and silicon contents, but above 3% Cu and 1% Si the trend reversed. However, total percent elongation and impact energy of the ternary and quaternary alloys decreased with increasing copper and silicon contents. T6 heat treatment further increased the hardness and tensile strength of ternary Zn–15Al–3Cu and quaternary Zn–15Al–3Cu–1Si alloys by altering their microstructures. Mechanical test results obtained from the experimental alloys were discussed in terms of their chemical compositions and microstructures. It was concluded that ternary Zn–15Al–3Cu and quaternary Zn–15Al–3Cu–1Si alloys can be successfully substituted for some non-ferrous commercial alloys including ZAMAK and ZA alloys, bronzes and brasses in engineering applications.

Microstructure and mechanical properties of Zn–15Al-based ternary and quaternary alloys

One binary ZnAl27- and five ZnAl27-based ternary alloys containing 1–5% Cu were produced by permanent mould casting. Their friction and wear properties were examined using a block-on-ring test machine after determining their hardness and tensile strength. It was observed that the hardness and tensile strength of the ZnAl27-based ternary alloys increased with increasing copper content up to 2% due to solid-solution hardening, above which their tensile strength decreased, while hardness continued to increase. This is attributed to the formation of copper-rich e and T′ phases, which reduce the solid-solution hardening of the alloys. It was found that the wear volume loss of the ZnAl27-based alloys decreased with increasing copper content up to 2% but showed a small increase above this level. Therefore, it was concluded that the wear resistance of ZnAl27-based alloys containing 1 to 5% Cu correlates well with their tensile strength. In addition, smearing and scratches were found to be the main features of the wear surfaces of the ZnAl27-based alloys under static loading and lubricated sliding conditions.

Effect of Copper Content on the Mechanical and Tribological Properties of ZnAl27-Based Alloys

In this study, a binary Al–12Si, eight ternary Al–12Si–Sr, and six quaternary Al–12Si–0.1Sr–(0.2–1)Mg alloys were produced by permanent mold casting. It was observed that microstructure of the binary alloy consisted of the phases of aluminum rich α grains (dendrites), primary silicon, plate like β and eutectic Al–Si containing needle like silicon particles. The ternary alloys have fine and globular (modified) eutectic silicon particles and higher volume fraction of α (Al) dendrites than binary alloys. They also contained Al4Sr phase after 0.02 wt% Sr, in addition to the phases in the binary alloy. This phase got coarse when the strontium ratio exceeded 0.1%. It was observed that the plate like β phase seen in the binary alloys transformed into the fibrous form δ phase in the ternary alloys. Magnesium addition resulted in transformation of δ phase into script like π phase, and the formation of lamellar like Mg2Si phase when the ratio of it in the quaternary alloys reached the 0.6 wt%. The lamellar like form of Mg2Si phase changed to Chinese-script type after the 0.6 wt% Mg. The results showed that hardness, yield and tensile strength of the Al–12Si–Sr alloys increased with increasing strontium content up to 0.1 wt%. The results also showed that hardness of the quaternary alloys increased with increasing magnesium content, while yield and tensile strength increased only up to 0.6 wt% Mg.

Effect of Strontium and Magnesium Additions on the Microstructure and Mechanical Properties of Al–12Si Alloys

In this study, Al-5Zn, Al-15Zn, Al-25Zn and Al-35Zn alloys containing 5, 15, 25 and 35 wt% Zn, respectively were produced by permanent mold casting. Their microstructures and mechanical properties were investigated using metallography and universal hardness and tensile tests. Cutting tests of the alloys produced were carried out in a vertical machining center. During the tests, the cutting forces were continuously measured and saved by a software. The roughness of the machined surfaces of the alloy samples was measured accordance with the standard of ISO 4287. It was observed that Al-(5–15)Zn alloys exhibit single phase (aluminum rich α) microstructure while Al-(25–35)Zn alloys exhibit two-phase microstructure consisting of α and zinc rich η. As the zinc content increased the hardness and tensile strength of the alloys increased, but their elongation to fracture decreased. Cutting force, surface roughness, formation of built-up edge (BUE) and built-up layer (BUL), and the size of the chip occurring in the machining of the alloys decreased with increasing zinc content. The machining of the Al-(5-35)Zn alloys with uncoated WC tools results in both lower cutting forces and better surface quality compared to titanium-aluminum-nitride (TiAlN) coated tools. The changes in the cutting properties of the tested alloys with the increasing zinc content were discussed in the based on changes in structural and mechanical properties.

Ali Paşa Hekimoğlu

Papers

Effect of copper content on the mechanical and sliding wear properties of monotectoid-based zinc-aluminium-copper alloys

Microstructure and mechanical properties of Zn–15Al-based ternary and quaternary alloys

Effect of Copper Content on the Mechanical and Tribological Properties of ZnAl27-Based Alloys

Effect of Strontium and Magnesium Additions on the Microstructure and Mechanical Properties of Al–12Si Alloys

Effect of Zinc Content and Cutting Tool Coating on the Machinability of the Al-(5–35) Zn Alloys