Transient liquid phase (TLP) bonding of Al7075 to Ti-6Al-4V alloy

The present paper describes the mechanical properties of a friction welded joint between Ti–6Al–4V alloy and Al–Mg alloy (AA5052). The Ti–6Al–4V/AA5052–H112 joint, made at a friction speed of 27.5 rev s−1, friction pressure of 30 MPa, friction time of 3.0 s, and forge pressure of 60 MPa, had 100% joint efficiency and fractured in the AA5052–H112 base metal. The Ti–6Al–4V/AA5052–H34 joint, made under the same friction welding conditions, did not achieve 100% joint efficiency and it fractured in the AA5052–H34 base metal because the AA5052–H34 base metal had softened under friction heating. The joints made at low friction speed or using short friction time showed fracture at the welded interface because a sufficient quantity of heat for welding could not be produced. However, the joints made at high friction speed or using long friction time were also fractured at the welded interface: in this instance, the welded interface also had an intermetallic compound layer consisting of Ti2Mg3Al18. The Ti–6A...

Mechanical properties of friction welded joint between Ti–6Al–4V alloy and Al–Mg alloy (AA5052)

The growth of an intermediate layer, consisting of an intermetallic compound phase, in a friction welded joint between pure Ti and pure Al heated at 853 K for up to 173 ks (580°C, 48 h) was elucidated via an in situ (direct) and continuous observation method using a high temperature optical microscope. The following conclusions were reached. The layer grew from the Al substrate to the Ti substrate, and neither a linear nor a parabolic time dependence could be used to describe the rate of layer growth. The layer growth stopped for some time (i.e. several hours) after every heating interval of approximately 36 ks (10 h). That is, several plateaus appeared during heat treatment. It is thought that nucleation, and growth of such nuclei, of the Al- Ti binary intermetallic phase are necessary for layer growth. The interlayer growth rate for joints between pure Ti and highly pure Al was higher than that for joints between pure Ti and commercially pure Al. This is due to the Si content in the Al base met...

In situ observation of interlayer growth during heat treatment of friction weld joint between pure titanium and pure aluminium

The interlayer growth at interfaces of Ti/Al–1%Mn and Ti/Al–4·6%Mg weld joints was studied by postweld heat treatment. The heating temperatures ranged from 676 to 873 K (400–600°C) and maximum heating time was 360 ks (100 h). The basic mechanism of interlayer growth for pure Ti/pure Al friction weld joint was also estimated. The interlayer growth rate of Ti/Al–4·6%Mg joint was much faster than for the Ti/ Al–1%Mn joint. The interlayer mainly consisted of (Al,Si)3Ti for the Ti/Al–1%Mn joint, and Al18Mg3Ti2 for the Ti/Al–4·6%Mg joint. While the interlayer grew from Al alloy substrate to the Ti side for the Ti/Al–1%Mn joint, it grew from the Ti substrate to the Al alloy side for the Ti/Al–4·6%Mg joint. The interlayer growth stopped for several hours on heating for 36 ks (10 h). Neither linear nor parabolic time-dependence relations could be exactly fit to the interlayer growth rate for both joints. The interlayer growth of Ti/Al–1%Mn was proportional to heating time raised to approximately 0·85. The...

Interlayer growth at interfaces of Ti/Al–1%Mn, Ti/Al–4·6%Mg and Ti/pure Al friction weld joints by post-weld heat treatment

Investigation of fracture for friction welded joint between pure nickel and pure aluminium with post-weld heat treatment

This paper describes the microstructural change of a Ti/Al friction weld interface during heat treatment at 673K, 773K, and 873K. TEM/EDS observations of a commercially pure Al/Ti weld confirmed that only the Al3Ti phase formed at the weld interface during heat treatment at 773K or 873K, while no intermetallic compound formed during heat treatment at 673K. The Al3Ti phase was composed of fine equiaxed grains nucleated at the interface boundary and grown up to a few microns in diameter during the heat treatment. Although the Si content was less than 0.12at% in the commercial Al/Ti weld, approximately 5at% Si was solved into the Al3Ti phase and a large amount of Si segregation, almost 20at%, was detected at the Ti/Al3Ti interface. No silicide formed during the heat treatment and the sugregation of Si was always observed. The observation of the specimen heat treated at 673K confirmed that Si segregation took place before the formation of the Al3Ti phase. The faster growth rate of the Al3Ti phase in the highly pure Al/Ti weld at 873K strongly suggested that the Si segregation retarded growth of the Al3Ti phase. The growth rate of the Al3Ti phase heat treated at 873K was in proportion to the square root of the holding time in the early stage of the heat treatment up to 3.6ksec, while it was linearly proportional to the holding time in the latter stage of the heat treatment.

https://www.jstage.jst.go.jp/article/jsms1963/44/505/44_505_1224/_pdf

Takumi Hamajima

Papers

Microstructural Change of Weld Interface in Ti/Al Friction Weld during Heat Treatment.