Effect of Heat Treatment on the Electrochemical and Mechanical Behavior of the Ti6Al4V Alloy

The effects of heat treatment on the hardness and electrochemical behavior of the Ti6Al4V alloy were studied. Two heat treatments were performed: one below (800 °C) and the other above (1050 °C) its beta transformation temperature (T= 980 ± 20 °C) and cooled using three conditions: water quenching, normalizing, and furnace. A microstructure observed using Optical Microscopy showed dependence on the heat treatment temperature applied; mainly three microstructures were obtained: martensitic, globular, and lamellar. Besides, alpha and beta phases were characterized by X-ray diffraction (XRD) technique. The Berkovich tests were performed to measure the hardness and reduced modulus (E). The Ti6Al4V alloy treated at 1050 °C and air-cooled exhibited hardness values closer to those of the Ti6Al4V as-received alloy. Electrochemical tests were carried out to analyze the electrochemical behavior after 7-day immersion in Hank’s solution at 37 °C and pH 7.40. Open Circuit Potentials (E) showed less negative values for Ti6Al4V and Ti6Al4V alloys, suggesting ennoblement of these materials. Furthermore, these alloys exhibited an outstanding electrochemical behavior compared to the Ti6Al4V as-received alloy by Electrochemical Impedance Spectroscopy (EIS) technique.The authors thank David Pérez-Risco for sharing his experience and useful advice on Berkovich Nano-indenter at the National Metallurgical Research Center (CENIM-CSIC Madrid, Spain), allowing this work to be carried out. Mercedes Paulina Chávez-Díaz thanks the National Science and Technology Council (CONACyT) for a doctoral fellowship to hold a research stay at CENIM-CSIC. This work was supported by the Government of Spain, through the Ministry of Economy and Competitiveness [MAT2015-67750-C3-1]. Elsa Miriam Arce-Estrada and Román Cabrera-Sierra wish to thank the National Research System (SNI) for the distinction of its members and the stipend received

Global urban environmental change drives adaptation in white clover

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale