News

News

Room-temperature cycling cools down strengthening in aluminium alloys

Data: 2019-09-18
Views: 250

Room-temperature cycling cools down strengthening in aluminium alloys


Aluminium alloys are widely used in many industrial applications including automobiles and aeroplanes, on account of their light weight. However, the wide-spread use of such alloys was contingent on the discovery of precipitate strengthening as a means for improving the tensile properties of these alloys necessary for most applications. Discovered over a hundred years ago, the technique involves heating alloys to elevated temperatures, which allows nanoscale secondary phases to precipitate in the metal. These precipitates hinder dislocation motion throughout the material and greatly increase their tensile strength. Now, however, Australian researchers led by Christopher Hutchinson at Monash University have developed a room-temperature cycling technique that reproduces and improves these material properties much more quickly and cheaply.


The inclusion of nanoscale precipitates into high-performance alloys is a key mechanism for improving their tensile properties for many industrial applications. These precipitates are often of a different phase from the bulk alloy and require large energy barriers to nucleate as well as increased diffusion for their formations. Hence, some of the most used aluminium alloys are “baked” for hours at between 120 °C and 200 °C to promote precipitate nucleation and growth. This technique, though in use since 1906, is highly demanding in terms of both time and energy.


Here, the researchers have developed a novel technique dubbed cyclic strengthening (CS) which, as its name suggests, cyclically stretches and compresses the metal without heating it. This cyclic stress creates vacancies in the materials by dislocation motion, which allows for increased diffusion and hence precipitate formation, leading to improved mechanical properties of the alloys.


The properties of the aluminium alloys treated by CS give equal or better strengths to heat-treatment but also improved elongation behaviour. This is explained in part due to the different nature of micro-damage sustained by the metals during CS treatment. Indeed, a caveat of thermally aging alloys is the formation of precipitate free zones (PFZs) near grain boundaries. The high diffusion rates at elevated temperatures allow precipitates and vacancies to annihilate at grain boundaries leaving 20–200 nm weak precipitate-free regions near grain boundaries. The CS method, however, does not induce the formation of such zones and instead, homogenously distributes strength throughout the material, which explains in part the improved extension behaviour of the alloys.


The researchers have not yet fully determined the exact nature of the precipitates formed during CS treatment but they are much smaller, on the order of 1 to 2 nm, than those formed during thermal treatment. What is even more notable is that the CS technique is highly rapid allowing for treatments that take only minutes to complete using high cycling frequencies. This new method provides a cheap and extremely quick alternative to traditional precipitate strengthening methods for aluminium alloys overstepping a century-old technique.


Via: https://physicsworld.com

News / Recommended news More
2020 - 01 - 22
Heusler alloys are magnetic materials made from three different metals that are not magnetic individually. The alloys are used broadly for their magnetic and thermoelectric properties, and their ability to regain their original shape after being deformed, known as shape memory. Investigations by Tohoku University's advanced materials scientist An-Pang Tsai and colleagues now show that these materi...
2020 - 01 - 10
3D printed Titanium alloys under an electron microscope: sample on the left with large, elongated crystals was printed conventionally, while sample on the right with finer, shorter crystals was printed sitting on a ultrasonic generator. Credit: RMIT UniversityResearchers have used sound vibrations to shake metal alloy grains into tighter formation during 3-D printing.A study can have a signif...
2020 - 01 - 03
The ability to 3D print titanium-alloy objects certainly does open up some intriguing possibilities. That said, the finished items aren't always as strong as they could be. Now, new research suggests that adding copper to those alloys could make a big difference.Typically, when objects are being 3D printed out of titanium alloy, a laser is used to selectively melt a powder consisting of titan...
2019 - 12 - 27
Russian scientists have developed a new generation of extrahard alloys, which will be used for the creation of equipment for mining in the extreme conditions of the Arctic region, said Yevgeny Levashov, the project manager and a professor of the Russian National University of Science and Technology.According to Levashov, the new alloys were created as part of the state program for the development ...
Share:
Uniris Exhibition Shanghai Co., Ltd.
Shanghai Branch
Tel:4000 778 909
E-mail:irisexpo@163.com
  
Guangzhou Branch
Tel:020-8327 6389
E-mail:pmchina@unifair.com

CCEC CHINA official website
犀牛云提供企业云服务
Scan the QR code to visit the official website by phone