Laser welded assembly having a heat affected zone reinforcement and method of making the same

1. A welded assembly comprising,

a first work piece having an external surface, a faying surface opposite the external surface, and a cross-sectional thickness (T 1 ) defined between the external surface and the faying surface of the first work piece;

a second work piece having an external surface, a faying surface opposite the external surface, and a cross-sectional thickness (T 2 ) defined between the external surface and the faying surface of the second work piece, wherein the faying surface of the first work piece is in abutting contact with the faying surface of the second work piece to define a faying interface;

a weld seam having a core fusion zone extending completely through the first work piece from the external surface of the first work piece through the faying interface and at least partially into the cross-sectional thickness (T 2 ) of the second work piece, wherein the weld seam includes a center linear segment extending along the external surface of the first work piece; and

a protruding fusion zone extending laterally from at least one side of the core fusion zone and extending vertically through only a portion of the cross-sectional thickness (T 1 ) from the external surface to proximal to the faying surface of the first work piece.

2. The weld assembly of claim 1 , wherein the protruding fusion zone includes a curved boundary defined between a first radius (R 1 ) adjacent to the external surface of the first work piece and a second radius (R 2 ) proximal to the faying interface, wherein the first radius (R 1 ) and second radius (R 2 ) extend radially from an axis along the core fusion zone and wherein the first radius (R 1 ) is greater than the second radius (R 2 ).

3. The weld assembly of claim 2 , wherein the first work piece includes a softened anneal zone following the boundary of the protruding fusion zone.

4. The weld assembly of claim 3 , wherein the boundary of the protruding fusion zone includes a bowl shape profile defined between the first radius (R 1 ) and the second radius (R 2 ).

5. The weld assembly of claim 4 , wherein a tangent line (L) extending from a point on the boundary of the protruding fusion zone to the faying interface at the core fusion zone defines an angle (a) less than 90 degrees relative to the faying interface.

6. The weld assembly of claim 5 , wherein the angle (a) is between about 15 degrees to about 75 degrees.

7. The weld assembly of claim 1 , wherein the protruding fusion zone is formed by post-heating the first work piece by directing a laser onto the external surface of the first work piece along a predetermined lateral portion of the core fusion zone.

8. The weld assembly of claim 1 , wherein the protruding fusion zone is concurrently formed with the core fusion zone by directing a defocused laser onto the external surface of the first work piece.

9. The weld assembly of claim 1 , wherein the weld seam is a laser weld seam.

10. A laser welded automotive structural component comprising:

a first work piece having an external surface, a faying surface opposite the external surface, and a cross-sectional thickness (T 1 ) defined between the external surface and the faying surface of the first work piece;

a second work piece having an external surface, a faying surface opposite the external surface, and a thickness (T 2 ) defined between the external surface and the faying surface of the second work piece, wherein the faying surface of the first work piece is in abutting contact with the faying surface of the second work piece to define a faying interface;

a weld seam having a core fusion zone extending from the external surface of the first work piece through the faying interface and at least partially into the thickness (T 2 ) of the second work piece, wherein the weld seam includes a center linear segment extending along the external surface of the first work piece; and

a protruding fusion zone extending laterally from the core fusion zone through a portion of the cross-sectional thickness (T 1 ) from the external surface to proximal to the faying surface within the first work piece, wherein the protruding fusion zone extends along at least one side of the center linear segment;

wherein the weld seam defines an elongated C-shape extending from an end of the center linear segment, and

wherein the protruding fusion zone is adjacent to a predetermined portion of the elongated C-shape.

11. The laser welded automotive structural component of claim 10 , wherein the protruding fusion zone includes a boundary defined between a first radius (R 1 ) adjacent to the external surface of the first work piece and a second radius (R 2 ) proximal to the faying interface, wherein the boundary defined between the first radius (R 1 ) and second radius (R 2 ) defines a curved bowl shape profile, and wherein R 1 is greater than R 2 .