Weight reduction and load bearing capacity Modern transport requires faster and lighter units. Construction materials with favourable strength to weigth ratio, like aluminium, are preferred. The use of fusion welding reduces this advantage. Market adoption FSW was introduced to the market in the early 90’s. Despite the fact that the strength reduction problem is not solved, the market adoption of FSW has shown that new joining methods for aluminium are necessary. HyBond - A BONDING REVOLUTION To compensate the strength loss, the dimensions must be increased. HYB is a new patented But increased dimensions imply increased weight, fuel consumption and climate gas release. In addition to capture existing markets, disruptive innovations will reveal new markets and new customers. Thus, it is expected that HYB will gain market shares from both FSW and GMAW. HYB - the second generation ‘solid state’ joining process for aluminium. joining method for aluminium. Solid state joining of aluminium plates and profiles is now possible using filler metal Ownership 1 kg reduced weight in every car reduces the total yearly petrol consumption in the US by 300 million litres. Using HYB as joining method will reduce climate gas release. Load bearing capacity addition. HyBond - Aintellectual BONDING REVOLUTION All patents and property rights belong to HyBond AS, which is a joint venture owned by LANGSET and NTNU. In other products, the combination of low weigth and high load-bearing capacity is critical. Hence, joining without strength reduction is of outmoust importance. Traditional fusion welding of aluminium leads to 50 % HAZ strength reduction. It also leads to the formation of a fusion zone (FZ) with low cracking and corrosion resistance. The fact that fusion is not necessary to create metallic Faculty of Natural Sciences and Technology, Department of Materials Science and Engineering bonding has lead to this new development Traditional welding of aluminium Fusion welding (GMAW) does not reduce the strength of steel after welding. For aluminium the situation is different. The microstructural changes occurring during welding lead to permanent mechanical degradation with a severe softening problem in the heat affected zone (HAZ) and cracking and corrosion problems in the fusion zone (FZ). Temperature profile of aluminium The new HYB method The basic idea behind the new innovation, called the Hybrid Metal Extrusion & Bonding (HYB) process, has been to develop a low temperature solid state method which does not lead to HAZ softening and where addition of filler metal is possible. The optical micrograph shows the cross section of two AA6005 base plates being joined with an AA6082 filler wire at 400°C. The resulting Vickers hardness profile across the joint is shown above. Metallic bonding is a result of interatomic attraction between the atoms. If the oxide layer is removed and the atoms are brought sufficently close to each other, full metallic bonding will be achieved. The positively charged atom cores are bonded by mutual attraction to the negatively charged electrons. Strength profile of aluminium Results and status The HYB technology Continuous extrusion is applied to produce an oxide-free filler metal. The filler, which is slightly wider, is forced into the groove. Hence, shear deformation with oxide removal produces metallic bonding between the two components to be joined and the filler metal. If the temperature is below 300 °C, there will be no softening. Successful joining of Al-Mg-Si alloys at 275 °C has been obtained. This process temperature is below the HAZ softening temperature. A new extruder with increased robustness is under development and ready for testing in 2012. Phase diagram Reheating of aluminium above 350-400 °C reduces the strength in the HAZ by 50 % and consequently the loadbearing capacity of the component. However, metallic bonding can be obtained without fusion. It can even be achieved at room temperature. Several attempts (like FSW) have been made in order to obtain bonding at temperatures where the metal is still in the ‘solid state’. Although FSW only reaches a process temperature of about 550 °C, it still leads to the formation of a wide HAZ and the same softening problems as in GMAW. More info and downloads: www.hybond.no
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