In the laser treatment of a workpiece (9), e.g. for surface hardening, melting, alloying, cladding, welding or cutting, the adverse effect of reflectivity of the surface, when a pure, monochromatic laser (6) is used, is remedied by the simultaneous application of a relatively shorter wavelength beam (1). The two beams (1)(5) may be combined by a beam coupler (4) or may reach the workpiece (9) by separate optical paths (not shown). The shorter wavelength beam (1) improves the coupling efficiency of the higher- powered laser beam (5).

Laser Material Processing

Graded microstructure and mechanical properties of additive manufactured Ti–6Al–4V via electron beam melting

In the last two decades or so, spinning and flow forming have gradually matured as metal forming processes for the production of engineering components in small to medium batch quantities. Combined spinning and flow forming techniques are being utilised increasingly due to the great flexibility provided for producing complicated parts nearer to net shape, enabling customers to optimise designs and reduce weight and cost, all of which are vital, especially in automotive industries. In this paper, process details of spinning and flow forming are introduced. The state of the art is described and developments in terms of research and industrial applications are reviewed. Also, the direction of research and development for future industrial applications are indicated.

A review of spinning, shear forming and flow forming processes

Dynamic recrystallization behavior of a typical nickel-based superalloy during hot deformation

Recent progress on polymer materials for additive manufacturing

The flow behavior of 7050 aluminum alloy was investigated by means of isothermal compression tests. Isothermal compression of 7050 aluminum alloy was carried out on a Gleeble-1500 thermal simulation machine at the deformation temperatures ranging from 593 K to 743 K, the strain rates ranging from 0.01 s−1 to 20.0 s−1, and the height reductions of 30%, 50% and 70%. The characteristics of stress–strain curves are determined by the interaction of work hardening, dynamic recovery and dynamic recrystallization. The flow stress decreases with the increasing of deformation temperature and the decreasing of strain rate. The relationship between microstructure and processing parameters was analyzed. The constitutive equations for characterizing the flow behavior during the whole deformation process had been established, based on the experimental results and the kinetic analysis. The average relative error between the calculated and the experimental flow stress is 5.73%, which indicates that the constitutive equations can be used to predict the flow behavior of 7050 aluminum alloy accurately during high temperature deformation.

The flow behavior and constitutive equations in isothermal compression of 7050 aluminum alloy

Constitutive model for high temperature deformation of titanium alloys using internal state variables

The 300M steel was heated in an electric furnace at the temperatures of 850, 900, 950, 1000, 1050 °C, and holding time of 5, 10, 30, 60, 90, 120 min. The grain size of austenite was measured by using the linear intercept method on Olympus PMG3 metallographic microscope. The experimental results show that grain size of austenite increases with the increasing of heating temperature and holding time, and the grain growth model of austenite in 300M steel is in the following: d  = 4.04 × 10 6 t 0.17 exp( − (1.32 × 10 5 / RT )).

The growth behavior of austenite grain in the heating process of 300M steel

The variation of strain rate sensitivity exponent and strain hardening exponent in isothermal compression of Ti–6Al–4V alloy

The deformation behavior of isothermally compressed Ti–6Al–4V alloy in the deformation temperature range from 1093 K to 1303 K, the strain rate range from 0.001 s −1 to 10.0 s −1 and the height reduction range from 20% to 60% has been investigated in depth. Effect of the strain on the flow stress, the grain size and the apparent activation energy for deformation of isothermally compressed Ti–6Al–4V alloy is analyzed. The results show that the apparent activation energy for deformation and the grain size of isothermally compressed Ti–6Al–4V alloy in the α + β two-phase region vary slightly with strain: the activation energy increases with strain after an early drop as the primary α grain size varies with strain. On the other hand, the apparent activation energy for deformation of isothermally compressed Ti–6Al–4V alloy in the β single-phase region increases firstly with the increasing of strain and then does that slightly in the strain range from 0.3 to 0.7. A processing map of the isothermally compressed Ti–6Al–4V alloy is constructed at a strain of 0.6. The processing map of isothermally compressed Ti–6Al–4V alloy exhibits that the optimal processing parameters are the deformation temperature of 1143 K and the strain rate of 0.001 s −1 . Meanwhile, two instability domains in the processing map of isothermally compressed Ti–6Al–4V alloy are as follows: one is in the deformation temperature range from 1093 K to 1183 K and the strain rate range from 0.011 s −1 to 2.02 s −1 , and another is in the deformation temperature range from 1243 K to 1303 K and the strain rate range from 1.0 s −1 to 10.0 s −1 .

Miaoquan Li

Papers

The flow behavior and constitutive equations in isothermal compression of 7050 aluminum alloy

Constitutive model for high temperature deformation of titanium alloys using internal state variables

The growth behavior of austenite grain in the heating process of 300M steel

The variation of strain rate sensitivity exponent and strain hardening exponent in isothermal compression of Ti–6Al–4V alloy

Effect of the strain on the deformation behavior of isothermally compressed Ti―6Al―4V alloy